Merge pull request #15481 from ziglang/use-mem-intrinsics

actually use the new memory intrinsics

116 files changed, 630 insertions, 591 deletions

diff --git a/lib/compiler_rt/udivmodei4.zig b/lib/compiler_rt/udivmodei4.zig
index 1a18612015..354a926b81 100644
--- a/lib/compiler_rt/udivmodei4.zig
+++ b/lib/compiler_rt/udivmodei4.zig
@@ -29,8 +29,8 @@ inline fn limb_set(x: []u32, i: usize, v: u32) void {
 
 // Uses Knuth's Algorithm D, 4.3.1, p. 272.
 fn divmod(q: ?[]u32, r: ?[]u32, u: []const u32, v: []const u32) !void {
-    if (q) |q_| std.mem.set(u32, q_[0..], 0);
-    if (r) |r_| std.mem.set(u32, r_[0..], 0);
+    if (q) |q_| @memset(q_[0..], 0);
+    if (r) |r_| @memset(r_[0..], 0);
 
     if (u.len == 0 or v.len == 0) return error.DivisionByZero;
 
@@ -44,7 +44,7 @@ fn divmod(q: ?[]u32, r: ?[]u32, u: []const u32, v: []const u32) !void {
     }
 
     if (n > m) {
-        if (r) |r_| std.mem.copy(u32, r_[0..], u[0..]);
+        if (r) |r_| @memcpy(r_[0..u.len], u);
         return;
     }
 
diff --git a/lib/std/Build.zig b/lib/std/Build.zig
index 34806adf48..f23b3ba5aa 100644
--- a/lib/std/Build.zig
+++ b/lib/std/Build.zig
@@ -1693,10 +1693,10 @@ pub fn constructCMacro(allocator: Allocator, name: []const u8, value: ?[]const u
         u8,
         name.len + if (value) |value_slice| value_slice.len + 1 else 0,
     ) catch |err| if (err == error.OutOfMemory) @panic("Out of memory") else unreachable;
-    mem.copy(u8, macro, name);
+    @memcpy(macro[0..name.len], name);
     if (value) |value_slice| {
         macro[name.len] = '=';
-        mem.copy(u8, macro[name.len + 1 ..], value_slice);
+        @memcpy(macro[name.len + 1 ..][0..value_slice.len], value_slice);
     }
     return macro;
 }
diff --git a/lib/std/Build/Cache.zig b/lib/std/Build/Cache.zig
index cae779a306..9139311785 100644
--- a/lib/std/Build/Cache.zig
+++ b/lib/std/Build/Cache.zig
@@ -388,7 +388,7 @@ pub const Manifest = struct {
         self.hash.hasher = hasher_init;
         self.hash.hasher.update(&bin_digest);
 
-        mem.copy(u8, &manifest_file_path, &self.hex_digest);
+        @memcpy(manifest_file_path[0..self.hex_digest.len], &self.hex_digest);
         manifest_file_path[hex_digest_len..][0..ext.len].* = ext.*;
 
         if (self.files.items.len == 0) {
diff --git a/lib/std/Build/CompileStep.zig b/lib/std/Build/CompileStep.zig
index b71298ce6a..d5a135e24b 100644
--- a/lib/std/Build/CompileStep.zig
+++ b/lib/std/Build/CompileStep.zig
@@ -1139,7 +1139,7 @@ fn appendModuleArgs(
         // We'll use this buffer to store the name we decide on
         var buf = try b.allocator.alloc(u8, dep.name.len + 32);
         // First, try just the exposed dependency name
-        std.mem.copy(u8, buf, dep.name);
+        @memcpy(buf[0..dep.name.len], dep.name);
         var name = buf[0..dep.name.len];
         var n: usize = 0;
         while (names.contains(name)) {
diff --git a/lib/std/Build/RunStep.zig b/lib/std/Build/RunStep.zig
index 435c7369d0..ce2dd0234a 100644
--- a/lib/std/Build/RunStep.zig
+++ b/lib/std/Build/RunStep.zig
@@ -822,9 +822,19 @@ fn runCommand(
             },
         },
         .zig_test => {
+            const prefix: []const u8 = p: {
+                if (result.stdio.test_metadata) |tm| {
+                    if (tm.next_index <= tm.names.len) {
+                        const name = tm.testName(tm.next_index - 1);
+                        break :p b.fmt("while executing test '{s}', ", .{name});
+                    }
+                }
+                break :p "";
+            };
             const expected_term: std.process.Child.Term = .{ .Exited = 0 };
             if (!termMatches(expected_term, result.term)) {
-                return step.fail("the following command {} (expected {}):\n{s}", .{
+                return step.fail("{s}the following command {} (expected {}):\n{s}", .{
+                    prefix,
                     fmtTerm(result.term),
                     fmtTerm(expected_term),
                     try Step.allocPrintCmd(arena, self.cwd, final_argv),
@@ -832,8 +842,8 @@ fn runCommand(
             }
             if (!result.stdio.test_results.isSuccess()) {
                 return step.fail(
-                    "the following test command failed:\n{s}",
-                    .{try Step.allocPrintCmd(arena, self.cwd, final_argv)},
+                    "{s}the following test command failed:\n{s}",
+                    .{ prefix, try Step.allocPrintCmd(arena, self.cwd, final_argv) },
                 );
             }
         },
@@ -922,6 +932,7 @@ const StdIoResult = struct {
     stdout_null: bool,
     stderr_null: bool,
     test_results: Step.TestResults,
+    test_metadata: ?TestMetadata,
 };
 
 fn evalZigTest(
@@ -1057,6 +1068,7 @@ fn evalZigTest(
             .skip_count = skip_count,
             .leak_count = leak_count,
         },
+        .test_metadata = metadata,
     };
 }
 
@@ -1172,6 +1184,7 @@ fn evalGeneric(self: *RunStep, child: *std.process.Child) !StdIoResult {
         .stdout_null = stdout_null,
         .stderr_null = stderr_null,
         .test_results = .{},
+        .test_metadata = null,
     };
 }
 
diff --git a/lib/std/Progress.zig b/lib/std/Progress.zig
index dba7166398..e3c5fc20dd 100644
--- a/lib/std/Progress.zig
+++ b/lib/std/Progress.zig
@@ -374,7 +374,7 @@ fn bufWrite(self: *Progress, end: *usize, comptime format: []const u8, args: any
             self.columns_written += self.output_buffer.len - end.*;
             end.* = self.output_buffer.len;
             const suffix = "... ";
-            std.mem.copy(u8, self.output_buffer[self.output_buffer.len - suffix.len ..], suffix);
+            @memcpy(self.output_buffer[self.output_buffer.len - suffix.len ..], suffix);
         },
     }
 }
diff --git a/lib/std/Thread.zig b/lib/std/Thread.zig
index f2a78100ad..119328b2a8 100644
--- a/lib/std/Thread.zig
+++ b/lib/std/Thread.zig
@@ -56,7 +56,7 @@ pub fn setName(self: Thread, name: []const u8) SetNameError!void {
 
     const name_with_terminator = blk: {
         var name_buf: [max_name_len:0]u8 = undefined;
-        std.mem.copy(u8, &name_buf, name);
+        @memcpy(name_buf[0..name.len], name);
         name_buf[name.len] = 0;
         break :blk name_buf[0..name.len :0];
     };
diff --git a/lib/std/array_hash_map.zig b/lib/std/array_hash_map.zig
index bf43f24bc0..55b9aac6e4 100644
--- a/lib/std/array_hash_map.zig
+++ b/lib/std/array_hash_map.zig
@@ -578,9 +578,9 @@ pub fn ArrayHashMapUnmanaged(
             self.entries.len = 0;
             if (self.index_header) |header| {
                 switch (header.capacityIndexType()) {
-                    .u8 => mem.set(Index(u8), header.indexes(u8), Index(u8).empty),
-                    .u16 => mem.set(Index(u16), header.indexes(u16), Index(u16).empty),
-                    .u32 => mem.set(Index(u32), header.indexes(u32), Index(u32).empty),
+                    .u8 => @memset(header.indexes(u8), Index(u8).empty),
+                    .u16 => @memset(header.indexes(u16), Index(u16).empty),
+                    .u32 => @memset(header.indexes(u32), Index(u32).empty),
                 }
             }
         }
diff --git a/lib/std/array_list.zig b/lib/std/array_list.zig
index 1791482bc4..cbca601b82 100644
--- a/lib/std/array_list.zig
+++ b/lib/std/array_list.zig
@@ -120,7 +120,7 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             }
 
             const new_memory = try allocator.alignedAlloc(T, alignment, self.items.len);
-            mem.copy(T, new_memory, self.items);
+            @memcpy(new_memory, self.items);
             @memset(self.items, undefined);
             self.clearAndFree();
             return new_memory;
@@ -170,7 +170,7 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             self.items.len += items.len;
 
             mem.copyBackwards(T, self.items[i + items.len .. self.items.len], self.items[i .. self.items.len - items.len]);
-            mem.copy(T, self.items[i .. i + items.len], items);
+            @memcpy(self.items[i..][0..items.len], items);
         }
 
         /// Replace range of elements `list[start..start+len]` with `new_items`.
@@ -182,15 +182,15 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             const range = self.items[start..after_range];
 
             if (range.len == new_items.len)
-                mem.copy(T, range, new_items)
+                @memcpy(range[0..new_items.len], new_items)
             else if (range.len < new_items.len) {
                 const first = new_items[0..range.len];
                 const rest = new_items[range.len..];
 
-                mem.copy(T, range, first);
+                @memcpy(range[0..first.len], first);
                 try self.insertSlice(after_range, rest);
             } else {
-                mem.copy(T, range, new_items);
+                @memcpy(range[0..new_items.len], new_items);
                 const after_subrange = start + new_items.len;
 
                 for (self.items[after_range..], 0..) |item, i| {
@@ -260,7 +260,7 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             const new_len = old_len + items.len;
             assert(new_len <= self.capacity);
             self.items.len = new_len;
-            mem.copy(T, self.items[old_len..], items);
+            @memcpy(self.items[old_len..][0..items.len], items);
         }
 
         /// Append an unaligned slice of items to the list. Allocates more
@@ -306,18 +306,22 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
         /// Append a value to the list `n` times.
         /// Allocates more memory as necessary.
         /// Invalidates pointers if additional memory is needed.
-        pub fn appendNTimes(self: *Self, value: T, n: usize) Allocator.Error!void {
+        /// The function is inline so that a comptime-known `value` parameter will
+        /// have a more optimal memset codegen in case it has a repeated byte pattern.
+        pub inline fn appendNTimes(self: *Self, value: T, n: usize) Allocator.Error!void {
             const old_len = self.items.len;
             try self.resize(self.items.len + n);
-            mem.set(T, self.items[old_len..self.items.len], value);
+            @memset(self.items[old_len..self.items.len], value);
         }
 
         /// Append a value to the list `n` times.
         /// Asserts the capacity is enough. **Does not** invalidate pointers.
-        pub fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
+        /// The function is inline so that a comptime-known `value` parameter will
+        /// have a more optimal memset codegen in case it has a repeated byte pattern.
+        pub inline fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
             const new_len = self.items.len + n;
             assert(new_len <= self.capacity);
-            mem.set(T, self.items.ptr[self.items.len..new_len], value);
+            @memset(self.items.ptr[self.items.len..new_len], value);
             self.items.len = new_len;
         }
 
@@ -397,7 +401,7 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
                 self.capacity = new_capacity;
             } else {
                 const new_memory = try self.allocator.alignedAlloc(T, alignment, new_capacity);
-                mem.copy(T, new_memory, self.items);
+                @memcpy(new_memory[0..self.items.len], self.items);
                 self.allocator.free(old_memory);
                 self.items.ptr = new_memory.ptr;
                 self.capacity = new_memory.len;
@@ -596,7 +600,7 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
             }
 
             const new_memory = try allocator.alignedAlloc(T, alignment, self.items.len);
-            mem.copy(T, new_memory, self.items);
+            @memcpy(new_memory, self.items);
             @memset(self.items, undefined);
             self.clearAndFree(allocator);
             return new_memory;
@@ -647,7 +651,7 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
             self.items.len += items.len;
 
             mem.copyBackwards(T, self.items[i + items.len .. self.items.len], self.items[i .. self.items.len - items.len]);
-            mem.copy(T, self.items[i .. i + items.len], items);
+            @memcpy(self.items[i..][0..items.len], items);
         }
 
         /// Replace range of elements `list[start..start+len]` with `new_items`
@@ -716,7 +720,7 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
             const new_len = old_len + items.len;
             assert(new_len <= self.capacity);
             self.items.len = new_len;
-            mem.copy(T, self.items[old_len..], items);
+            @memcpy(self.items[old_len..][0..items.len], items);
         }
 
         /// Append the slice of items to the list. Allocates more
@@ -766,19 +770,23 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
         /// Append a value to the list `n` times.
         /// Allocates more memory as necessary.
         /// Invalidates pointers if additional memory is needed.
-        pub fn appendNTimes(self: *Self, allocator: Allocator, value: T, n: usize) Allocator.Error!void {
+        /// The function is inline so that a comptime-known `value` parameter will
+        /// have a more optimal memset codegen in case it has a repeated byte pattern.
+        pub inline fn appendNTimes(self: *Self, allocator: Allocator, value: T, n: usize) Allocator.Error!void {
             const old_len = self.items.len;
             try self.resize(allocator, self.items.len + n);
-            mem.set(T, self.items[old_len..self.items.len], value);
+            @memset(self.items[old_len..self.items.len], value);
         }
 
         /// Append a value to the list `n` times.
         /// **Does not** invalidate pointers.
         /// Asserts the capacity is enough.
-        pub fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
+        /// The function is inline so that a comptime-known `value` parameter will
+        /// have a more optimal memset codegen in case it has a repeated byte pattern.
+        pub inline fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
             const new_len = self.items.len + n;
             assert(new_len <= self.capacity);
-            mem.set(T, self.items.ptr[self.items.len..new_len], value);
+            @memset(self.items.ptr[self.items.len..new_len], value);
             self.items.len = new_len;
         }
 
@@ -815,7 +823,7 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
                 },
             };
 
-            mem.copy(T, new_memory, self.items[0..new_len]);
+            @memcpy(new_memory, self.items[0..new_len]);
             allocator.free(old_memory);
             self.items = new_memory;
             self.capacity = new_memory.len;
@@ -877,7 +885,7 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
                 self.capacity = new_capacity;
             } else {
                 const new_memory = try allocator.alignedAlloc(T, alignment, new_capacity);
-                mem.copy(T, new_memory, self.items);
+                @memcpy(new_memory[0..self.items.len], self.items);
                 allocator.free(old_memory);
                 self.items.ptr = new_memory.ptr;
                 self.capacity = new_memory.len;
diff --git a/lib/std/base64.zig b/lib/std/base64.zig
index d9bf7d4a07..758c7c8b58 100644
--- a/lib/std/base64.zig
+++ b/lib/std/base64.zig
@@ -309,11 +309,11 @@ test "base64 padding dest overflow" {
     const input = "foo";
 
     var expect: [128]u8 = undefined;
-    std.mem.set(u8, &expect, 0);
+    @memset(&expect, 0);
     _ = url_safe.Encoder.encode(expect[0..url_safe.Encoder.calcSize(input.len)], input);
 
     var got: [128]u8 = undefined;
-    std.mem.set(u8, &got, 0);
+    @memset(&got, 0);
     _ = url_safe.Encoder.encode(&got, input);
 
     try std.testing.expectEqualSlices(u8, &expect, &got);
diff --git a/lib/std/bit_set.zig b/lib/std/bit_set.zig
index 292d099303..b7dfc8d529 100644
--- a/lib/std/bit_set.zig
+++ b/lib/std/bit_set.zig
@@ -738,7 +738,7 @@ pub const DynamicBitSetUnmanaged = struct {
             // fill in any new masks
             if (new_masks > old_masks) {
                 const fill_value = std.math.boolMask(MaskInt, fill);
-                std.mem.set(MaskInt, self.masks[old_masks..new_masks], fill_value);
+                @memset(self.masks[old_masks..new_masks], fill_value);
             }
         }
 
@@ -765,7 +765,7 @@ pub const DynamicBitSetUnmanaged = struct {
         const num_masks = numMasks(self.bit_length);
         var copy = Self{};
         try copy.resize(new_allocator, self.bit_length, false);
-        std.mem.copy(MaskInt, copy.masks[0..num_masks], self.masks[0..num_masks]);
+        @memcpy(copy.masks[0..num_masks], self.masks[0..num_masks]);
         return copy;
     }
 
diff --git a/lib/std/bounded_array.zig b/lib/std/bounded_array.zig
index 8a4c2db64b..be32093fe7 100644
--- a/lib/std/bounded_array.zig
+++ b/lib/std/bounded_array.zig
@@ -73,7 +73,7 @@ pub fn BoundedArrayAligned(
         /// Copy the content of an existing slice.
         pub fn fromSlice(m: []const T) error{Overflow}!Self {
             var list = try init(m.len);
-            std.mem.copy(T, list.slice(), m);
+            @memcpy(list.slice(), m);
             return list;
         }
 
@@ -165,7 +165,7 @@ pub fn BoundedArrayAligned(
             try self.ensureUnusedCapacity(items.len);
             self.len += items.len;
             mem.copyBackwards(T, self.slice()[i + items.len .. self.len], self.constSlice()[i .. self.len - items.len]);
-            mem.copy(T, self.slice()[i .. i + items.len], items);
+            @memcpy(self.slice()[i..][0..items.len], items);
         }
 
         /// Replace range of elements `slice[start..start+len]` with `new_items`.
@@ -181,14 +181,14 @@ pub fn BoundedArrayAligned(
             var range = self.slice()[start..after_range];
 
             if (range.len == new_items.len) {
-                mem.copy(T, range, new_items);
+                @memcpy(range[0..new_items.len], new_items);
             } else if (range.len < new_items.len) {
                 const first = new_items[0..range.len];
                 const rest = new_items[range.len..];
-                mem.copy(T, range, first);
+                @memcpy(range[0..first.len], first);
                 try self.insertSlice(after_range, rest);
             } else {
-                mem.copy(T, range, new_items);
+                @memcpy(range[0..new_items.len], new_items);
                 const after_subrange = start + new_items.len;
                 for (self.constSlice()[after_range..], 0..) |item, i| {
                     self.slice()[after_subrange..][i] = item;
@@ -243,9 +243,9 @@ pub fn BoundedArrayAligned(
         /// Append the slice of items to the slice, asserting the capacity is already
         /// enough to store the new items.
         pub fn appendSliceAssumeCapacity(self: *Self, items: []const T) void {
-            const oldlen = self.len;
+            const old_len = self.len;
             self.len += items.len;
-            mem.copy(T, self.slice()[oldlen..], items);
+            @memcpy(self.slice()[old_len..][0..items.len], items);
         }
 
         /// Append a value to the slice `n` times.
@@ -253,7 +253,7 @@ pub fn BoundedArrayAligned(
         pub fn appendNTimes(self: *Self, value: T, n: usize) error{Overflow}!void {
             const old_len = self.len;
             try self.resize(old_len + n);
-            mem.set(T, self.slice()[old_len..self.len], value);
+            @memset(self.slice()[old_len..self.len], value);
         }
 
         /// Append a value to the slice `n` times.
@@ -262,7 +262,7 @@ pub fn BoundedArrayAligned(
             const old_len = self.len;
             self.len += n;
             assert(self.len <= buffer_capacity);
-            mem.set(T, self.slice()[old_len..self.len], value);
+            @memset(self.slice()[old_len..self.len], value);
         }
 
         pub const Writer = if (T != u8)
@@ -329,7 +329,7 @@ test "BoundedArray" {
     try testing.expectEqual(a.popOrNull(), 0);
     try testing.expectEqual(a.popOrNull(), null);
     var unused = a.unusedCapacitySlice();
-    mem.set(u8, unused[0..8], 2);
+    @memset(unused[0..8], 2);
     unused[8] = 3;
     unused[9] = 4;
     try testing.expectEqual(unused.len, a.capacity());
diff --git a/lib/std/buf_set.zig b/lib/std/buf_set.zig
index 9d6d7ed1e6..90ee86e12d 100644
--- a/lib/std/buf_set.zig
+++ b/lib/std/buf_set.zig
@@ -97,7 +97,7 @@ pub const BufSet = struct {
 
     fn copy(self: *const BufSet, value: []const u8) ![]const u8 {
         const result = try self.hash_map.allocator.alloc(u8, value.len);
-        mem.copy(u8, result, value);
+        @memcpy(result, value);
         return result;
     }
 };
diff --git a/lib/std/child_process.zig b/lib/std/child_process.zig
index bd67d344c7..f5ca72ed39 100644
--- a/lib/std/child_process.zig
+++ b/lib/std/child_process.zig
@@ -259,7 +259,7 @@ pub const ChildProcess = struct {
 
     fn fifoToOwnedArrayList(fifo: *std.io.PollFifo) std.ArrayList(u8) {
         if (fifo.head > 0) {
-            std.mem.copy(u8, fifo.buf[0..fifo.count], fifo.buf[fifo.head .. fifo.head + fifo.count]);
+            @memcpy(fifo.buf[0..fifo.count], fifo.buf[fifo.head..][0..fifo.count]);
         }
         const result = std.ArrayList(u8){
             .items = fifo.buf[0..fifo.count],
@@ -1436,9 +1436,9 @@ pub fn createNullDelimitedEnvMap(arena: mem.Allocator, env_map: *const EnvMap) !
         var i: usize = 0;
         while (it.next()) |pair| : (i += 1) {
             const env_buf = try arena.allocSentinel(u8, pair.key_ptr.len + pair.value_ptr.len + 1, 0);
-            mem.copy(u8, env_buf, pair.key_ptr.*);
+            @memcpy(env_buf[0..pair.key_ptr.len], pair.key_ptr.*);
             env_buf[pair.key_ptr.len] = '=';
-            mem.copy(u8, env_buf[pair.key_ptr.len + 1 ..], pair.value_ptr.*);
+            @memcpy(env_buf[pair.key_ptr.len + 1 ..][0..pair.value_ptr.len], pair.value_ptr.*);
             envp_buf[i] = env_buf.ptr;
         }
         assert(i == envp_count);
diff --git a/lib/std/compress/deflate.zig b/lib/std/compress/deflate.zig
index 7b079a6039..2fe5969067 100644
--- a/lib/std/compress/deflate.zig
+++ b/lib/std/compress/deflate.zig
@@ -12,6 +12,20 @@ pub const Decompressor = inflate.Decompressor;
 pub const compressor = deflate.compressor;
 pub const decompressor = inflate.decompressor;
 
+/// Copies elements from a source `src` slice into a destination `dst` slice.
+/// The copy never returns an error but might not be complete if the destination is too small.
+/// Returns the number of elements copied, which will be the minimum of `src.len` and `dst.len`.
+/// TODO: remove this smelly function
+pub fn copy(dst: []u8, src: []const u8) usize {
+    if (dst.len <= src.len) {
+        @memcpy(dst, src[0..dst.len]);
+        return dst.len;
+    } else {
+        @memcpy(dst[0..src.len], src);
+        return src.len;
+    }
+}
+
 test {
     _ = @import("deflate/token.zig");
     _ = @import("deflate/bits_utils.zig");
diff --git a/lib/std/compress/deflate/compressor.zig b/lib/std/compress/deflate/compressor.zig
index 6c21875941..e2cbafe520 100644
--- a/lib/std/compress/deflate/compressor.zig
+++ b/lib/std/compress/deflate/compressor.zig
@@ -10,7 +10,6 @@ const Allocator = std.mem.Allocator;
 const deflate_const = @import("deflate_const.zig");
 const fast = @import("deflate_fast.zig");
 const hm_bw = @import("huffman_bit_writer.zig");
-const mu = @import("mem_utils.zig");
 const token = @import("token.zig");
 
 pub const Compression = enum(i5) {
@@ -296,7 +295,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
         fn fillDeflate(self: *Self, b: []const u8) u32 {
             if (self.index >= 2 * window_size - (min_match_length + max_match_length)) {
                 // shift the window by window_size
-                mem.copy(u8, self.window, self.window[window_size .. 2 * window_size]);
+                mem.copyForwards(u8, self.window, self.window[window_size .. 2 * window_size]);
                 self.index -= window_size;
                 self.window_end -= window_size;
                 if (self.block_start >= window_size) {
@@ -328,7 +327,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
                     }
                 }
             }
-            var n = mu.copy(self.window[self.window_end..], b);
+            const n = std.compress.deflate.copy(self.window[self.window_end..], b);
             self.window_end += n;
             return @intCast(u32, n);
         }
@@ -369,7 +368,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
                 b = b[b.len - window_size ..];
             }
             // Add all to window.
-            mem.copy(u8, self.window, b);
+            @memcpy(self.window[0..b.len], b);
             var n = b.len;
 
             // Calculate 256 hashes at the time (more L1 cache hits)
@@ -543,7 +542,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
             self.hash_offset = 1;
             self.tokens = try self.allocator.alloc(token.Token, max_flate_block_tokens);
             self.tokens_count = 0;
-            mem.set(token.Token, self.tokens, 0);
+            @memset(self.tokens, 0);
             self.length = min_match_length - 1;
             self.offset = 0;
             self.byte_available = false;
@@ -706,7 +705,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
         }
 
         fn fillStore(self: *Self, b: []const u8) u32 {
-            var n = mu.copy(self.window[self.window_end..], b);
+            const n = std.compress.deflate.copy(self.window[self.window_end..], b);
             self.window_end += n;
             return @intCast(u32, n);
         }
@@ -841,9 +840,9 @@ pub fn Compressor(comptime WriterType: anytype) type {
             s.hash_head = try allocator.alloc(u32, hash_size);
             s.hash_prev = try allocator.alloc(u32, window_size);
             s.hash_match = try allocator.alloc(u32, max_match_length - 1);
-            mem.set(u32, s.hash_head, 0);
-            mem.set(u32, s.hash_prev, 0);
-            mem.set(u32, s.hash_match, 0);
+            @memset(s.hash_head, 0);
+            @memset(s.hash_prev, 0);
+            @memset(s.hash_match, 0);
 
             switch (options.level) {
                 .no_compression => {
@@ -936,8 +935,8 @@ pub fn Compressor(comptime WriterType: anytype) type {
                 .best_compression,
                 => {
                     self.chain_head = 0;
-                    mem.set(u32, self.hash_head, 0);
-                    mem.set(u32, self.hash_prev, 0);
+                    @memset(self.hash_head, 0);
+                    @memset(self.hash_prev, 0);
                     self.hash_offset = 1;
                     self.index = 0;
                     self.window_end = 0;
@@ -1091,8 +1090,8 @@ test "bulkHash4" {
         // double the test data
         var out = try testing.allocator.alloc(u8, x.out.len * 2);
         defer testing.allocator.free(out);
-        mem.copy(u8, out[0..x.out.len], x.out);
-        mem.copy(u8, out[x.out.len..], x.out);
+        @memcpy(out[0..x.out.len], x.out);
+        @memcpy(out[x.out.len..], x.out);
 
         var j: usize = 4;
         while (j < out.len) : (j += 1) {
diff --git a/lib/std/compress/deflate/decompressor.zig b/lib/std/compress/deflate/decompressor.zig
index e5cfbb0f6b..6c232c598e 100644
--- a/lib/std/compress/deflate/decompressor.zig
+++ b/lib/std/compress/deflate/decompressor.zig
@@ -9,7 +9,6 @@ const ArrayList = std.ArrayList;
 const bu = @import("bits_utils.zig");
 const ddec = @import("dict_decoder.zig");
 const deflate_const = @import("deflate_const.zig");
-const mu = @import("mem_utils.zig");
 
 const max_match_offset = deflate_const.max_match_offset;
 const end_block_marker = deflate_const.end_block_marker;
@@ -159,7 +158,7 @@ const HuffmanDecoder = struct {
                 if (sanity) {
                     // initialize to a known invalid chunk code (0) to see if we overwrite
                     // this value later on
-                    mem.set(u16, self.links[off], 0);
+                    @memset(self.links[off], 0);
                 }
                 try self.sub_chunks.append(off);
             }
@@ -451,7 +450,7 @@ pub fn Decompressor(comptime ReaderType: type) type {
         pub fn read(self: *Self, output: []u8) Error!usize {
             while (true) {
                 if (self.to_read.len > 0) {
-                    var n = mu.copy(output, self.to_read);
+                    const n = std.compress.deflate.copy(output, self.to_read);
                     self.to_read = self.to_read[n..];
                     if (self.to_read.len == 0 and
                         self.err != null)
diff --git a/lib/std/compress/deflate/deflate_fast.zig b/lib/std/compress/deflate/deflate_fast.zig
index 2009af2611..c86d181cb5 100644
--- a/lib/std/compress/deflate/deflate_fast.zig
+++ b/lib/std/compress/deflate/deflate_fast.zig
@@ -237,7 +237,7 @@ pub const DeflateFast = struct {
         }
         self.cur += @intCast(i32, src.len);
         self.prev_len = @intCast(u32, src.len);
-        mem.copy(u8, self.prev[0..self.prev_len], src);
+        @memcpy(self.prev[0..self.prev_len], src);
         return;
     }
 
@@ -566,11 +566,11 @@ test "best speed match 2/2" {
     for (cases) |c| {
         var previous = try testing.allocator.alloc(u8, c.previous);
         defer testing.allocator.free(previous);
-        mem.set(u8, previous, 0);
+        @memset(previous, 0);
 
         var current = try testing.allocator.alloc(u8, c.current);
         defer testing.allocator.free(current);
-        mem.set(u8, current, 0);
+        @memset(current, 0);
 
         var e = DeflateFast{
             .prev = previous,
diff --git a/lib/std/compress/deflate/deflate_fast_test.zig b/lib/std/compress/deflate/deflate_fast_test.zig
index f8efa80630..1c771d925a 100644
--- a/lib/std/compress/deflate/deflate_fast_test.zig
+++ b/lib/std/compress/deflate/deflate_fast_test.zig
@@ -123,13 +123,13 @@ test "best speed max match offset" {
                 var src = try testing.allocator.alloc(u8, src_len);
                 defer testing.allocator.free(src);
 
-                mem.copy(u8, src, abc);
+                @memcpy(src[0..abc.len], abc);
                 if (!do_match_before) {
-                    var src_offset: usize = @intCast(usize, offset - @as(i32, xyz.len));
-                    mem.copy(u8, src[src_offset..], xyz);
+                    const src_offset: usize = @intCast(usize, offset - @as(i32, xyz.len));
+                    @memcpy(src[src_offset..][0..xyz.len], xyz);
                 }
-                var src_offset: usize = @intCast(usize, offset);
-                mem.copy(u8, src[src_offset..], abc);
+                const src_offset: usize = @intCast(usize, offset);
+                @memcpy(src[src_offset..][0..abc.len], abc);
 
                 var compressed = ArrayList(u8).init(testing.allocator);
                 defer compressed.deinit();
diff --git a/lib/std/compress/deflate/dict_decoder.zig b/lib/std/compress/deflate/dict_decoder.zig
index bf21572827..d9f240e7b4 100644
--- a/lib/std/compress/deflate/dict_decoder.zig
+++ b/lib/std/compress/deflate/dict_decoder.zig
@@ -47,7 +47,8 @@ pub const DictDecoder = struct {
         self.wr_pos = 0;
 
         if (dict != null) {
-            mem.copy(u8, self.hist, dict.?[dict.?.len -| self.hist.len..]);
+            const src = dict.?[dict.?.len -| self.hist.len..];
+            @memcpy(self.hist[0..src.len], src);
             self.wr_pos = @intCast(u32, dict.?.len);
         }
 
@@ -103,12 +104,15 @@ pub const DictDecoder = struct {
         self.wr_pos += 1;
     }
 
+    /// TODO: eliminate this function because the callsites should care about whether
+    /// or not their arguments alias and then they should directly call `@memcpy` or
+    /// `mem.copyForwards`.
     fn copy(dst: []u8, src: []const u8) u32 {
         if (src.len > dst.len) {
-            mem.copy(u8, dst, src[0..dst.len]);
+            mem.copyForwards(u8, dst, src[0..dst.len]);
             return @intCast(u32, dst.len);
         }
-        mem.copy(u8, dst, src);
+        mem.copyForwards(u8, dst[0..src.len], src);
         return @intCast(u32, src.len);
     }
 
diff --git a/lib/std/compress/deflate/huffman_code.zig b/lib/std/compress/deflate/huffman_code.zig
index e911e5219b..cf1dd71c75 100644
--- a/lib/std/compress/deflate/huffman_code.zig
+++ b/lib/std/compress/deflate/huffman_code.zig
@@ -202,7 +202,7 @@ pub const HuffmanEncoder = struct {
                     // more values in the level below
                     l.last_freq = l.next_pair_freq;
                     // Take leaf counts from the lower level, except counts[level] remains the same.
-                    mem.copy(u32, leaf_counts[level][0..level], leaf_counts[level - 1][0..level]);
+                    @memcpy(leaf_counts[level][0..level], leaf_counts[level - 1][0..level]);
                     levels[l.level - 1].needed = 2;
                 }
 
diff --git a/lib/std/compress/deflate/mem_utils.zig b/lib/std/compress/deflate/mem_utils.zig
deleted file mode 100644
index 32b55a1bb6..0000000000
--- a/lib/std/compress/deflate/mem_utils.zig
+++ /dev/null
@@ -1,15 +0,0 @@
-const std = @import("std");
-const math = std.math;
-const mem = std.mem;
-
-// Copies elements from a source `src` slice into a destination `dst` slice.
-// The copy never returns an error but might not be complete if the destination is too small.
-// Returns the number of elements copied, which will be the minimum of `src.len` and `dst.len`.
-pub fn copy(dst: []u8, src: []const u8) usize {
-    if (dst.len <= src.len) {
-        mem.copy(u8, dst[0..], src[0..dst.len]);
-    } else {
-        mem.copy(u8, dst[0..src.len], src[0..]);
-    }
-    return math.min(dst.len, src.len);
-}
diff --git a/lib/std/compress/lzma.zig b/lib/std/compress/lzma.zig
index 8bb8c19da1..ff05bc1c8b 100644
--- a/lib/std/compress/lzma.zig
+++ b/lib/std/compress/lzma.zig
@@ -75,9 +75,9 @@ pub fn Decompress(comptime ReaderType: type) type {
                 }
             }
             const input = self.to_read.items;
-            const n = math.min(input.len, output.len);
-            mem.copy(u8, output[0..n], input[0..n]);
-            mem.copy(u8, input, input[n..]);
+            const n = @min(input.len, output.len);
+            @memcpy(output[0..n], input[0..n]);
+            @memcpy(input[0 .. input.len - n], input[n..]);
             self.to_read.shrinkRetainingCapacity(input.len - n);
             return n;
         }
diff --git a/lib/std/compress/lzma/decode/rangecoder.zig b/lib/std/compress/lzma/decode/rangecoder.zig
index 5df10be060..5a2f309fe4 100644
--- a/lib/std/compress/lzma/decode/rangecoder.zig
+++ b/lib/std/compress/lzma/decode/rangecoder.zig
@@ -143,7 +143,7 @@ pub fn BitTree(comptime num_bits: usize) type {
         }
 
         pub fn reset(self: *Self) void {
-            mem.set(u16, &self.probs, 0x400);
+            @memset(&self.probs, 0x400);
         }
     };
 }
diff --git a/lib/std/compress/lzma/vec2d.zig b/lib/std/compress/lzma/vec2d.zig
index 1372d3592c..1ea3d1e8d5 100644
--- a/lib/std/compress/lzma/vec2d.zig
+++ b/lib/std/compress/lzma/vec2d.zig
@@ -13,7 +13,7 @@ pub fn Vec2D(comptime T: type) type {
         pub fn init(allocator: Allocator, value: T, size: struct { usize, usize }) !Self {
             const len = try math.mul(usize, size[0], size[1]);
             const data = try allocator.alloc(T, len);
-            mem.set(T, data, value);
+            @memset(data, value);
             return Self{
                 .data = data,
                 .cols = size[1],
@@ -26,7 +26,7 @@ pub fn Vec2D(comptime T: type) type {
         }
 
         pub fn fill(self: *Self, value: T) void {
-            mem.set(T, self.data, value);
+            @memset(self.data, value);
         }
 
         inline fn _get(self: Self, row: usize) ![]T {
diff --git a/lib/std/compress/xz/block.zig b/lib/std/compress/xz/block.zig
index 8d3d8f0353..520c335794 100644
--- a/lib/std/compress/xz/block.zig
+++ b/lib/std/compress/xz/block.zig
@@ -59,9 +59,9 @@ pub fn Decoder(comptime ReaderType: type) type {
             while (true) {
                 if (self.to_read.items.len > 0) {
                     const input = self.to_read.items;
-                    const n = std.math.min(input.len, output.len);
-                    std.mem.copy(u8, output[0..n], input[0..n]);
-                    std.mem.copy(u8, input, input[n..]);
+                    const n = @min(input.len, output.len);
+                    @memcpy(output[0..n], input[0..n]);
+                    std.mem.copyForwards(u8, input, input[n..]);
                     self.to_read.shrinkRetainingCapacity(input.len - n);
                     if (self.to_read.items.len == 0 and self.err != null) {
                         if (self.err.? == DecodeError.EndOfStreamWithNoError) {
diff --git a/lib/std/compress/zstandard/decode/block.zig b/lib/std/compress/zstandard/decode/block.zig
index 4b7353f63c..e2042650c6 100644
--- a/lib/std/compress/zstandard/decode/block.zig
+++ b/lib/std/compress/zstandard/decode/block.zig
@@ -293,10 +293,10 @@ pub const DecodeState = struct {
 
         try self.decodeLiteralsSlice(dest[write_pos..], sequence.literal_length);
         const copy_start = write_pos + sequence.literal_length - sequence.offset;
-        const copy_end = copy_start + sequence.match_length;
-        // NOTE: we ignore the usage message for std.mem.copy and copy with dest.ptr >= src.ptr
-        //       to allow repeats
-        std.mem.copy(u8, dest[write_pos + sequence.literal_length ..], dest[copy_start..copy_end]);
+        for (
+            dest[write_pos + sequence.literal_length ..][0..sequence.match_length],
+            dest[copy_start..][0..sequence.match_length],
+        ) |*d, s| d.* = s;
         self.written_count += sequence.match_length;
     }
 
@@ -311,7 +311,6 @@ pub const DecodeState = struct {
         try self.decodeLiteralsRingBuffer(dest, sequence.literal_length);
         const copy_start = dest.write_index + dest.data.len - sequence.offset;
         const copy_slice = dest.sliceAt(copy_start, sequence.match_length);
-        // TODO: would std.mem.copy and figuring out dest slice be better/faster?
         for (copy_slice.first) |b| dest.writeAssumeCapacity(b);
         for (copy_slice.second) |b| dest.writeAssumeCapacity(b);
         self.written_count += sequence.match_length;
@@ -444,9 +443,8 @@ pub const DecodeState = struct {
 
         switch (self.literal_header.block_type) {
             .raw => {
-                const literals_end = self.literal_written_count + len;
-                const literal_data = self.literal_streams.one[self.literal_written_count..literals_end];
-                std.mem.copy(u8, dest, literal_data);
+                const literal_data = self.literal_streams.one[self.literal_written_count..][0..len];
+                @memcpy(dest[0..len], literal_data);
                 self.literal_written_count += len;
                 self.written_count += len;
             },
@@ -615,8 +613,7 @@ pub fn decodeBlock(
         .raw => {
             if (src.len < block_size) return error.MalformedBlockSize;
             if (dest[written_count..].len < block_size) return error.DestTooSmall;
-            const data = src[0..block_size];
-            std.mem.copy(u8, dest[written_count..], data);
+            @memcpy(dest[written_count..][0..block_size], src[0..block_size]);
             consumed_count.* += block_size;
             decode_state.written_count += block_size;
             return block_size;
diff --git a/lib/std/crypto/25519/ed25519.zig b/lib/std/crypto/25519/ed25519.zig
index 66dcf3705b..6b9c1028b6 100644
--- a/lib/std/crypto/25519/ed25519.zig
+++ b/lib/std/crypto/25519/ed25519.zig
@@ -79,8 +79,8 @@ pub const Ed25519 = struct {
             const r_bytes = r.toBytes();
 
             var t: [64]u8 = undefined;
-            mem.copy(u8, t[0..32], &r_bytes);
-            mem.copy(u8, t[32..], &public_key.bytes);
+            t[0..32].* = r_bytes;
+            t[32..].* = public_key.bytes;
             var h = Sha512.init(.{});
             h.update(&t);
 
@@ -200,8 +200,8 @@ pub const Ed25519 = struct {
         /// Return the raw signature (r, s) in little-endian format.
         pub fn toBytes(self: Signature) [encoded_length]u8 {
             var bytes: [encoded_length]u8 = undefined;
-            mem.copy(u8, bytes[0 .. encoded_length / 2], &self.r);
-            mem.copy(u8, bytes[encoded_length / 2 ..], &self.s);
+            bytes[0 .. encoded_length / 2].* = self.r;
+            bytes[encoded_length / 2 ..].* = self.s;
             return bytes;
         }
 
@@ -260,8 +260,8 @@ pub const Ed25519 = struct {
             const pk_p = Curve.basePoint.clampedMul(az[0..32].*) catch return error.IdentityElement;
             const pk_bytes = pk_p.toBytes();
             var sk_bytes: [SecretKey.encoded_length]u8 = undefined;
-            mem.copy(u8, &sk_bytes, &ss);
-            mem.copy(u8, sk_bytes[seed_length..], &pk_bytes);
+            sk_bytes[0..ss.len].* = ss;
+            sk_bytes[seed_length..].* = pk_bytes;
             return KeyPair{
                 .public_key = PublicKey.fromBytes(pk_bytes) catch unreachable,
                 .secret_key = try SecretKey.fromBytes(sk_bytes),
@@ -373,7 +373,7 @@ pub const Ed25519 = struct {
         var z_batch: [count]Curve.scalar.CompressedScalar = undefined;
         for (&z_batch) |*z| {
             crypto.random.bytes(z[0..16]);
-            mem.set(u8, z[16..], 0);
+            @memset(z[16..], 0);
         }
 
         var zs_sum = Curve.scalar.zero;
@@ -444,8 +444,8 @@ pub const Ed25519 = struct {
                 };
 
                 var prefix: [64]u8 = undefined;
-                mem.copy(u8, prefix[0..32], h[32..64]);
-                mem.copy(u8, prefix[32..64], blind_h[32..64]);
+                prefix[0..32].* = h[32..64].*;
+                prefix[32..64].* = blind_h[32..64].*;
 
                 const blind_secret_key = BlindSecretKey{
                     .prefix = prefix,
diff --git a/lib/std/crypto/25519/edwards25519.zig b/lib/std/crypto/25519/edwards25519.zig
index df4f8467f9..a8ca8e2fb6 100644
--- a/lib/std/crypto/25519/edwards25519.zig
+++ b/lib/std/crypto/25519/edwards25519.zig
@@ -306,7 +306,7 @@ pub const Edwards25519 = struct {
         var pcs: [count][9]Edwards25519 = undefined;
 
         var bpc: [9]Edwards25519 = undefined;
-        mem.copy(Edwards25519, bpc[0..], basePointPc[0..bpc.len]);
+        @memcpy(&bpc, basePointPc[0..bpc.len]);
 
         for (ps, 0..) |p, i| {
             if (p.is_base) {
@@ -439,7 +439,7 @@ pub const Edwards25519 = struct {
         var u: [n * H.digest_length]u8 = undefined;
         var i: usize = 0;
         while (i < n * H.digest_length) : (i += H.digest_length) {
-            mem.copy(u8, u[i..][0..H.digest_length], u_0[0..]);
+            u[i..][0..H.digest_length].* = u_0;
             var j: usize = 0;
             while (i > 0 and j < H.digest_length) : (j += 1) {
                 u[i + j] ^= u[i + j - H.digest_length];
@@ -455,8 +455,8 @@ pub const Edwards25519 = struct {
         var px: [n]Edwards25519 = undefined;
         i = 0;
         while (i < n) : (i += 1) {
-            mem.set(u8, u_0[0 .. H.digest_length - h_l], 0);
-            mem.copy(u8, u_0[H.digest_length - h_l ..][0..h_l], u[i * h_l ..][0..h_l]);
+            @memset(u_0[0 .. H.digest_length - h_l], 0);
+            u_0[H.digest_length - h_l ..][0..h_l].* = u[i * h_l ..][0..h_l].*;
             px[i] = fromHash(u_0);
         }
         return px;
diff --git a/lib/std/crypto/25519/scalar.zig b/lib/std/crypto/25519/scalar.zig
index ff2e6aff80..fd6d42aebe 100644
--- a/lib/std/crypto/25519/scalar.zig
+++ b/lib/std/crypto/25519/scalar.zig
@@ -83,8 +83,8 @@ pub fn add(a: CompressedScalar, b: CompressedScalar) CompressedScalar {
 pub fn neg(s: CompressedScalar) CompressedScalar {
     const fs: [64]u8 = field_order_s ++ [_]u8{0} ** 32;
     var sx: [64]u8 = undefined;
-    mem.copy(u8, sx[0..32], s[0..]);
-    mem.set(u8, sx[32..], 0);
+    sx[0..32].* = s;
+    @memset(sx[32..], 0);
     var carry: u32 = 0;
     var i: usize = 0;
     while (i < 64) : (i += 1) {
@@ -593,7 +593,7 @@ const ScalarDouble = struct {
             limbs[i] = mem.readIntLittle(u64, bytes[i * 7 ..][0..8]) & 0xffffffffffffff;
         }
         limbs[i] = @as(u64, mem.readIntLittle(u32, bytes[i * 7 ..][0..4]));
-        mem.set(u64, limbs[5..], 0);
+        @memset(limbs[5..], 0);
         return ScalarDouble{ .limbs = limbs };
     }
 
diff --git a/lib/std/crypto/25519/x25519.zig b/lib/std/crypto/25519/x25519.zig
index 22bcf00136..b746a51968 100644
--- a/lib/std/crypto/25519/x25519.zig
+++ b/lib/std/crypto/25519/x25519.zig
@@ -37,7 +37,7 @@ pub const X25519 = struct {
                 break :sk random_seed;
             };
             var kp: KeyPair = undefined;
-            mem.copy(u8, &kp.secret_key, sk[0..]);
+            kp.secret_key = sk;
             kp.public_key = try X25519.recoverPublicKey(sk);
             return kp;
         }
@@ -120,8 +120,8 @@ test "x25519 rfc7748 one iteration" {
     var i: usize = 0;
     while (i < 1) : (i += 1) {
         const output = try X25519.scalarmult(k, u);
-        mem.copy(u8, u[0..], k[0..]);
-        mem.copy(u8, k[0..], output[0..]);
+        u = k;
+        k = output;
     }
 
     try std.testing.expectEqual(k, expected_output);
@@ -142,8 +142,8 @@ test "x25519 rfc7748 1,000 iterations" {
     var i: usize = 0;
     while (i < 1000) : (i += 1) {
         const output = try X25519.scalarmult(&k, &u);
-        mem.copy(u8, u[0..], k[0..]);
-        mem.copy(u8, k[0..], output[0..]);
+        u = k;
+        k = output;
     }
 
     try std.testing.expectEqual(k, expected_output);
@@ -163,8 +163,8 @@ test "x25519 rfc7748 1,000,000 iterations" {
     var i: usize = 0;
     while (i < 1000000) : (i += 1) {
         const output = try X25519.scalarmult(&k, &u);
-        mem.copy(u8, u[0..], k[0..]);
-        mem.copy(u8, k[0..], output[0..]);
+        u = k;
+        k = output;
     }
 
     try std.testing.expectEqual(k[0..], expected_output);
diff --git a/lib/std/crypto/Certificate.zig b/lib/std/crypto/Certificate.zig
index 0caffba363..ec4766322c 100644
--- a/lib/std/crypto/Certificate.zig
+++ b/lib/std/crypto/Certificate.zig
@@ -928,7 +928,7 @@ pub const rsa = struct {
     pub const PSSSignature = struct {
         pub fn fromBytes(comptime modulus_len: usize, msg: []const u8) [modulus_len]u8 {
             var result = [1]u8{0} ** modulus_len;
-            std.mem.copy(u8, &result, msg);
+            std.mem.copyForwards(u8, &result, msg);
             return result;
         }
 
@@ -1025,9 +1025,9 @@ pub const rsa = struct {
             //      initial zero octets.
             var m_p = try allocator.alloc(u8, 8 + Hash.digest_length + sLen);
             defer allocator.free(m_p);
-            std.mem.copy(u8, m_p, &([_]u8{0} ** 8));
-            std.mem.copy(u8, m_p[8..], &mHash);
-            std.mem.copy(u8, m_p[(8 + Hash.digest_length)..], salt);
+            std.mem.copyForwards(u8, m_p, &([_]u8{0} ** 8));
+            std.mem.copyForwards(u8, m_p[8..], &mHash);
+            std.mem.copyForwards(u8, m_p[(8 + Hash.digest_length)..], salt);
 
             // 13.  Let H' = Hash(M'), an octet string of length hLen.
             var h_p: [Hash.digest_length]u8 = undefined;
@@ -1047,7 +1047,7 @@ pub const rsa = struct {
 
             var hash = try allocator.alloc(u8, seed.len + c.len);
             defer allocator.free(hash);
-            std.mem.copy(u8, hash, seed);
+            std.mem.copyForwards(u8, hash, seed);
             var hashed: [Hash.digest_length]u8 = undefined;
 
             while (idx < len) {
@@ -1056,10 +1056,10 @@ pub const rsa = struct {
                 c[2] = @intCast(u8, (counter >> 8) & 0xFF);
                 c[3] = @intCast(u8, counter & 0xFF);
 
-                std.mem.copy(u8, hash[seed.len..], &c);
+                std.mem.copyForwards(u8, hash[seed.len..], &c);
                 Hash.hash(hash, &hashed, .{});
 
-                std.mem.copy(u8, out[idx..], &hashed);
+                std.mem.copyForwards(u8, out[idx..], &hashed);
                 idx += hashed.len;
 
                 counter += 1;
diff --git a/lib/std/crypto/aegis.zig b/lib/std/crypto/aegis.zig
index d7305b444a..2d37bacc3a 100644
--- a/lib/std/crypto/aegis.zig
+++ b/lib/std/crypto/aegis.zig
@@ -152,8 +152,8 @@ fn Aegis128LGeneric(comptime tag_bits: u9) type {
                 state.absorb(ad[i..][0..32]);
             }
             if (ad.len % 32 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. ad.len % 32], ad[i .. i + ad.len % 32]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. ad.len % 32], ad[i..][0 .. ad.len % 32]);
                 state.absorb(&src);
             }
             i = 0;
@@ -161,10 +161,10 @@ fn Aegis128LGeneric(comptime tag_bits: u9) type {
                 state.enc(c[i..][0..32], m[i..][0..32]);
             }
             if (m.len % 32 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. m.len % 32], m[i .. i + m.len % 32]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. m.len % 32], m[i..][0 .. m.len % 32]);
                 state.enc(&dst, &src);
-                mem.copy(u8, c[i .. i + m.len % 32], dst[0 .. m.len % 32]);
+                @memcpy(c[i..][0 .. m.len % 32], dst[0 .. m.len % 32]);
             }
             tag.* = state.mac(tag_bits, ad.len, m.len);
         }
@@ -185,8 +185,8 @@ fn Aegis128LGeneric(comptime tag_bits: u9) type {
                 state.absorb(ad[i..][0..32]);
             }
             if (ad.len % 32 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. ad.len % 32], ad[i .. i + ad.len % 32]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. ad.len % 32], ad[i..][0 .. ad.len % 32]);
                 state.absorb(&src);
             }
             i = 0;
@@ -194,11 +194,11 @@ fn Aegis128LGeneric(comptime tag_bits: u9) type {
                 state.dec(m[i..][0..32], c[i..][0..32]);
             }
             if (m.len % 32 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. m.len % 32], c[i .. i + m.len % 32]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. m.len % 32], c[i..][0 .. m.len % 32]);
                 state.dec(&dst, &src);
-                mem.copy(u8, m[i .. i + m.len % 32], dst[0 .. m.len % 32]);
-                mem.set(u8, dst[0 .. m.len % 32], 0);
+                @memcpy(m[i..][0 .. m.len % 32], dst[0 .. m.len % 32]);
+                @memset(dst[0 .. m.len % 32], 0);
                 const blocks = &state.blocks;
                 blocks[0] = blocks[0].xorBlocks(AesBlock.fromBytes(dst[0..16]));
                 blocks[4] = blocks[4].xorBlocks(AesBlock.fromBytes(dst[16..32]));
@@ -334,8 +334,8 @@ fn Aegis256Generic(comptime tag_bits: u9) type {
                 state.enc(&dst, ad[i..][0..16]);
             }
             if (ad.len % 16 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. ad.len % 16], ad[i .. i + ad.len % 16]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. ad.len % 16], ad[i..][0 .. ad.len % 16]);
                 state.enc(&dst, &src);
             }
             i = 0;
@@ -343,10 +343,10 @@ fn Aegis256Generic(comptime tag_bits: u9) type {
                 state.enc(c[i..][0..16], m[i..][0..16]);
             }
             if (m.len % 16 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. m.len % 16], m[i .. i + m.len % 16]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. m.len % 16], m[i..][0 .. m.len % 16]);
                 state.enc(&dst, &src);
-                mem.copy(u8, c[i .. i + m.len % 16], dst[0 .. m.len % 16]);
+                @memcpy(c[i..][0 .. m.len % 16], dst[0 .. m.len % 16]);
             }
             tag.* = state.mac(tag_bits, ad.len, m.len);
         }
@@ -367,8 +367,8 @@ fn Aegis256Generic(comptime tag_bits: u9) type {
                 state.enc(&dst, ad[i..][0..16]);
             }
             if (ad.len % 16 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. ad.len % 16], ad[i .. i + ad.len % 16]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. ad.len % 16], ad[i..][0 .. ad.len % 16]);
                 state.enc(&dst, &src);
             }
             i = 0;
@@ -376,11 +376,11 @@ fn Aegis256Generic(comptime tag_bits: u9) type {
                 state.dec(m[i..][0..16], c[i..][0..16]);
             }
             if (m.len % 16 != 0) {
-                mem.set(u8, src[0..], 0);
-                mem.copy(u8, src[0 .. m.len % 16], c[i .. i + m.len % 16]);
+                @memset(src[0..], 0);
+                @memcpy(src[0 .. m.len % 16], c[i..][0 .. m.len % 16]);
                 state.dec(&dst, &src);
-                mem.copy(u8, m[i .. i + m.len % 16], dst[0 .. m.len % 16]);
-                mem.set(u8, dst[0 .. m.len % 16], 0);
+                @memcpy(m[i..][0 .. m.len % 16], dst[0 .. m.len % 16]);
+                @memset(dst[0 .. m.len % 16], 0);
                 const blocks = &state.blocks;
                 blocks[0] = blocks[0].xorBlocks(AesBlock.fromBytes(&dst));
             }
@@ -457,7 +457,7 @@ fn AegisMac(comptime T: type) type {
             self.msg_len += b.len;
 
             const len_partial = @min(b.len, block_length - self.off);
-            mem.copy(u8, self.buf[self.off..][0..len_partial], b[0..len_partial]);
+            @memcpy(self.buf[self.off..][0..len_partial], b[0..len_partial]);
             self.off += len_partial;
             if (self.off < block_length) {
                 return;
@@ -470,7 +470,7 @@ fn AegisMac(comptime T: type) type {
                 self.state.absorb(b[i..][0..block_length]);
             }
             if (i != b.len) {
-                mem.copy(u8, self.buf[0..], b[i..]);
+                @memcpy(self.buf[0..], b[i..]);
                 self.off = b.len - i;
             }
         }
@@ -479,7 +479,7 @@ fn AegisMac(comptime T: type) type {
         pub fn final(self: *Self, out: *[mac_length]u8) void {
             if (self.off > 0) {
                 var pad = [_]u8{0} ** block_length;
-                mem.copy(u8, pad[0..], self.buf[0..self.off]);
+                @memcpy(pad[0..self.off], self.buf[0..self.off]);
                 self.state.absorb(&pad);
             }
             out.* = self.state.mac(T.tag_length * 8, self.msg_len, 0);
diff --git a/lib/std/crypto/aes_gcm.zig b/lib/std/crypto/aes_gcm.zig
index 4ec53371e6..660073d3ae 100644
--- a/lib/std/crypto/aes_gcm.zig
+++ b/lib/std/crypto/aes_gcm.zig
@@ -31,7 +31,7 @@ fn AesGcm(comptime Aes: anytype) type {
 
             var t: [16]u8 = undefined;
             var j: [16]u8 = undefined;
-            mem.copy(u8, j[0..nonce_length], npub[0..]);
+            j[0..nonce_length].* = npub;
             mem.writeIntBig(u32, j[nonce_length..][0..4], 1);
             aes.encrypt(&t, &j);
 
@@ -64,7 +64,7 @@ fn AesGcm(comptime Aes: anytype) type {
 
             var t: [16]u8 = undefined;
             var j: [16]u8 = undefined;
-            mem.copy(u8, j[0..nonce_length], npub[0..]);
+            j[0..nonce_length].* = npub;
             mem.writeIntBig(u32, j[nonce_length..][0..4], 1);
             aes.encrypt(&t, &j);
 
diff --git a/lib/std/crypto/aes_ocb.zig b/lib/std/crypto/aes_ocb.zig
index 83e33e5fca..6d5ce3779a 100644
--- a/lib/std/crypto/aes_ocb.zig
+++ b/lib/std/crypto/aes_ocb.zig
@@ -75,7 +75,7 @@ fn AesOcb(comptime Aes: anytype) type {
             if (leftover > 0) {
                 xorWith(&offset, lx.star);
                 var padded = [_]u8{0} ** 16;
-                mem.copy(u8, padded[0..leftover], a[i * 16 ..][0..leftover]);
+                @memcpy(padded[0..leftover], a[i * 16 ..][0..leftover]);
                 padded[leftover] = 1;
                 var e = xorBlocks(offset, padded);
                 aes_enc_ctx.encrypt(&e, &e);
@@ -88,7 +88,7 @@ fn AesOcb(comptime Aes: anytype) type {
             var nx = [_]u8{0} ** 16;
             nx[0] = @intCast(u8, @truncate(u7, tag_length * 8) << 1);
             nx[16 - nonce_length - 1] = 1;
-            mem.copy(u8, nx[16 - nonce_length ..], &npub);
+            nx[nx.len - nonce_length ..].* = npub;
 
             const bottom = @truncate(u6, nx[15]);
             nx[15] &= 0xc0;
@@ -132,14 +132,14 @@ fn AesOcb(comptime Aes: anytype) type {
                     xorWith(&offset, lt[@ctz(i + 1 + j)]);
                     offsets[j] = offset;
                     const p = m[(i + j) * 16 ..][0..16].*;
-                    mem.copy(u8, es[j * 16 ..][0..16], &xorBlocks(p, offsets[j]));
+                    es[j * 16 ..][0..16].* = xorBlocks(p, offsets[j]);
                     xorWith(&sum, p);
                 }
                 aes_enc_ctx.encryptWide(wb, &es, &es);
                 j = 0;
                 while (j < wb) : (j += 1) {
                     const e = es[j * 16 ..][0..16].*;
-                    mem.copy(u8, c[(i + j) * 16 ..][0..16], &xorBlocks(e, offsets[j]));
+                    c[(i + j) * 16 ..][0..16].* = xorBlocks(e, offsets[j]);
                 }
             }
             while (i < full_blocks) : (i += 1) {
@@ -147,7 +147,7 @@ fn AesOcb(comptime Aes: anytype) type {
                 const p = m[i * 16 ..][0..16].*;
                 var e = xorBlocks(p, offset);
                 aes_enc_ctx.encrypt(&e, &e);
-                mem.copy(u8, c[i * 16 ..][0..16], &xorBlocks(e, offset));
+                c[i * 16 ..][0..16].* = xorBlocks(e, offset);
                 xorWith(&sum, p);
             }
             const leftover = m.len % 16;
@@ -159,7 +159,7 @@ fn AesOcb(comptime Aes: anytype) type {
                     c[i * 16 + j] = pad[j] ^ x;
                 }
                 var e = [_]u8{0} ** 16;
-                mem.copy(u8, e[0..leftover], m[i * 16 ..][0..leftover]);
+                @memcpy(e[0..leftover], m[i * 16 ..][0..leftover]);
                 e[leftover] = 0x80;
                 xorWith(&sum, e);
             }
@@ -196,13 +196,13 @@ fn AesOcb(comptime Aes: anytype) type {
                     xorWith(&offset, lt[@ctz(i + 1 + j)]);
                     offsets[j] = offset;
                     const q = c[(i + j) * 16 ..][0..16].*;
-                    mem.copy(u8, es[j * 16 ..][0..16], &xorBlocks(q, offsets[j]));
+                    es[j * 16 ..][0..16].* = xorBlocks(q, offsets[j]);
                 }
                 aes_dec_ctx.decryptWide(wb, &es, &es);
                 j = 0;
                 while (j < wb) : (j += 1) {
                     const p = xorBlocks(es[j * 16 ..][0..16].*, offsets[j]);
-                    mem.copy(u8, m[(i + j) * 16 ..][0..16], &p);
+                    m[(i + j) * 16 ..][0..16].* = p;
                     xorWith(&sum, p);
                 }
             }
@@ -212,7 +212,7 @@ fn AesOcb(comptime Aes: anytype) type {
                 var e = xorBlocks(q, offset);
                 aes_dec_ctx.decrypt(&e, &e);
                 const p = xorBlocks(e, offset);
-                mem.copy(u8, m[i * 16 ..][0..16], &p);
+                m[i * 16 ..][0..16].* = p;
                 xorWith(&sum, p);
             }
             const leftover = m.len % 16;
@@ -224,7 +224,7 @@ fn AesOcb(comptime Aes: anytype) type {
                     m[i * 16 + j] = pad[j] ^ x;
                 }
                 var e = [_]u8{0} ** 16;
-                mem.copy(u8, e[0..leftover], m[i * 16 ..][0..leftover]);
+                @memcpy(e[0..leftover], m[i * 16 ..][0..leftover]);
                 e[leftover] = 0x80;
                 xorWith(&sum, e);
             }
diff --git a/lib/std/crypto/argon2.zig b/lib/std/crypto/argon2.zig
index 0112e81c6a..43dbe3e332 100644
--- a/lib/std/crypto/argon2.zig
+++ b/lib/std/crypto/argon2.zig
@@ -149,7 +149,7 @@ fn blake2bLong(out: []u8, in: []const u8) void {
         h.update(&outlen_bytes);
         h.update(in);
         h.final(&out_buf);
-        mem.copy(u8, out, out_buf[0..out.len]);
+        @memcpy(out, out_buf[0..out.len]);
         return;
     }
 
@@ -158,19 +158,19 @@ fn blake2bLong(out: []u8, in: []const u8) void {
     h.update(in);
     h.final(&out_buf);
     var out_slice = out;
-    mem.copy(u8, out_slice, out_buf[0 .. H.digest_length / 2]);
+    out_slice[0 .. H.digest_length / 2].* = out_buf[0 .. H.digest_length / 2].*;
     out_slice = out_slice[H.digest_length / 2 ..];
 
     var in_buf: [H.digest_length]u8 = undefined;
     while (out_slice.len > H.digest_length) {
-        mem.copy(u8, &in_buf, &out_buf);
+        in_buf = out_buf;
         H.hash(&in_buf, &out_buf, .{});
-        mem.copy(u8, out_slice, out_buf[0 .. H.digest_length / 2]);
+        out_slice[0 .. H.digest_length / 2].* = out_buf[0 .. H.digest_length / 2].*;
         out_slice = out_slice[H.digest_length / 2 ..];
     }
-    mem.copy(u8, &in_buf, &out_buf);
+    in_buf = out_buf;
     H.hash(&in_buf, &out_buf, .{ .expected_out_bits = out_slice.len * 8 });
-    mem.copy(u8, out_slice, out_buf[0..out_slice.len]);
+    @memcpy(out_slice, out_buf[0..out_slice.len]);
 }
 
 fn initBlocks(
@@ -494,7 +494,7 @@ pub fn kdf(
     if (params.t < 1 or params.p < 1) return KdfError.WeakParameters;
 
     var h0 = initHash(password, salt, params, derived_key.len, mode);
-    const memory = math.max(
+    const memory = @max(
         params.m / (sync_points * params.p) * (sync_points * params.p),
         2 * sync_points * params.p,
     );
@@ -877,7 +877,7 @@ test "kdf" {
             .hash = "1640b932f4b60e272f5d2207b9a9c626ffa1bd88d2349016",
         },
     };
-    inline for (test_vectors) |v| {
+    for (test_vectors) |v| {
         var want: [24]u8 = undefined;
         _ = try std.fmt.hexToBytes(&want, v.hash);
 
diff --git a/lib/std/crypto/ascon.zig b/lib/std/crypto/ascon.zig
index f37d9acea5..ae4bb57d29 100644
--- a/lib/std/crypto/ascon.zig
+++ b/lib/std/crypto/ascon.zig
@@ -34,7 +34,7 @@ pub fn State(comptime endian: builtin.Endian) type {
         /// Initialize the state from a slice of bytes.
         pub fn init(initial_state: [block_bytes]u8) Self {
             var state = Self{ .st = undefined };
-            mem.copy(u8, state.asBytes(), &initial_state);
+            @memcpy(state.asBytes(), &initial_state);
             state.endianSwap();
             return state;
         }
@@ -87,7 +87,7 @@ pub fn State(comptime endian: builtin.Endian) type {
             }
             if (i < bytes.len) {
                 var padded = [_]u8{0} ** 8;
-                mem.copy(u8, padded[0 .. bytes.len - i], bytes[i..]);
+                @memcpy(padded[0 .. bytes.len - i], bytes[i..]);
                 self.st[i / 8] = mem.readInt(u64, padded[0..], endian);
             }
         }
@@ -109,7 +109,7 @@ pub fn State(comptime endian: builtin.Endian) type {
             }
             if (i < bytes.len) {
                 var padded = [_]u8{0} ** 8;
-                mem.copy(u8, padded[0 .. bytes.len - i], bytes[i..]);
+                @memcpy(padded[0 .. bytes.len - i], bytes[i..]);
                 self.st[i / 8] ^= mem.readInt(u64, padded[0..], endian);
             }
         }
@@ -123,7 +123,7 @@ pub fn State(comptime endian: builtin.Endian) type {
             if (i < out.len) {
                 var padded = [_]u8{0} ** 8;
                 mem.writeInt(u64, padded[0..], self.st[i / 8], endian);
-                mem.copy(u8, out[i..], padded[0 .. out.len - i]);
+                @memcpy(out[i..], padded[0 .. out.len - i]);
             }
         }
 
@@ -138,16 +138,16 @@ pub fn State(comptime endian: builtin.Endian) type {
             }
             if (i < in.len) {
                 var padded = [_]u8{0} ** 8;
-                mem.copy(u8, padded[0 .. in.len - i], in[i..]);
+                @memcpy(padded[0 .. in.len - i], in[i..]);
                 const x = mem.readIntNative(u64, &padded) ^ mem.nativeTo(u64, self.st[i / 8], endian);
                 mem.writeIntNative(u64, &padded, x);
-                mem.copy(u8, out[i..], padded[0 .. in.len - i]);
+                @memcpy(out[i..], padded[0 .. in.len - i]);
             }
         }
 
         /// Set the words storing the bytes of a given range to zero.
         pub fn clear(self: *Self, from: usize, to: usize) void {
-            mem.set(u64, self.st[from / 8 .. (to + 7) / 8], 0);
+            @memset(self.st[from / 8 .. (to + 7) / 8], 0);
         }
 
         /// Clear the entire state, disabling compiler optimizations.
diff --git a/lib/std/crypto/bcrypt.zig b/lib/std/crypto/bcrypt.zig
index 2191ab0d9e..dda5f5e377 100644
--- a/lib/std/crypto/bcrypt.zig
+++ b/lib/std/crypto/bcrypt.zig
@@ -416,8 +416,8 @@ pub fn bcrypt(
 ) [dk_length]u8 {
     var state = State{};
     var password_buf: [73]u8 = undefined;
-    const trimmed_len = math.min(password.len, password_buf.len - 1);
-    mem.copy(u8, password_buf[0..], password[0..trimmed_len]);
+    const trimmed_len = @min(password.len, password_buf.len - 1);
+    @memcpy(password_buf[0..trimmed_len], password[0..trimmed_len]);
     password_buf[trimmed_len] = 0;
     var passwordZ = password_buf[0 .. trimmed_len + 1];
     state.expand(salt[0..], passwordZ);
@@ -626,7 +626,7 @@ const CryptFormatHasher = struct {
         crypto.random.bytes(&salt);
 
         const hash = crypt_format.strHashInternal(password, salt, params);
-        mem.copy(u8, buf, &hash);
+        @memcpy(buf[0..hash.len], &hash);
 
         return buf[0..pwhash_str_length];
     }
diff --git a/lib/std/crypto/benchmark.zig b/lib/std/crypto/benchmark.zig
index f512c513e7..696a9c3107 100644
--- a/lib/std/crypto/benchmark.zig
+++ b/lib/std/crypto/benchmark.zig
@@ -113,8 +113,8 @@ pub fn benchmarkKeyExchange(comptime DhKeyExchange: anytype, comptime exchange_c
         var i: usize = 0;
         while (i < exchange_count) : (i += 1) {
             const out = try DhKeyExchange.scalarmult(secret, public);
-            mem.copy(u8, secret[0..16], out[0..16]);
-            mem.copy(u8, public[0..16], out[16..32]);
+            secret[0..16].* = out[0..16].*;
+            public[0..16].* = out[16..32].*;
             mem.doNotOptimizeAway(&out);
         }
     }
diff --git a/lib/std/crypto/blake2.zig b/lib/std/crypto/blake2.zig
index 85c26ce599..316ea5e6b7 100644
--- a/lib/std/crypto/blake2.zig
+++ b/lib/std/crypto/blake2.zig
@@ -76,7 +76,7 @@ pub fn Blake2s(comptime out_bits: usize) type {
             comptime debug.assert(8 <= out_bits and out_bits <= 256);
 
             var d: Self = undefined;
-            mem.copy(u32, d.h[0..], iv[0..]);
+            d.h = iv;
 
             const key_len = if (options.key) |key| key.len else 0;
             // default parameters
@@ -93,7 +93,7 @@ pub fn Blake2s(comptime out_bits: usize) type {
                 d.h[7] ^= mem.readIntLittle(u32, context[4..8]);
             }
             if (key_len > 0) {
-                mem.set(u8, d.buf[key_len..], 0);
+                @memset(d.buf[key_len..], 0);
                 d.update(options.key.?);
                 d.buf_len = 64;
             }
@@ -112,7 +112,7 @@ pub fn Blake2s(comptime out_bits: usize) type {
             // Partial buffer exists from previous update. Copy into buffer then hash.
             if (d.buf_len != 0 and d.buf_len + b.len > 64) {
                 off += 64 - d.buf_len;
-                mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
+                @memcpy(d.buf[d.buf_len..][0..off], b[0..off]);
                 d.t += 64;
                 d.round(d.buf[0..], false);
                 d.buf_len = 0;
@@ -125,16 +125,17 @@ pub fn Blake2s(comptime out_bits: usize) type {
             }
 
             // Copy any remainder for next pass.
-            mem.copy(u8, d.buf[d.buf_len..], b[off..]);
-            d.buf_len += @intCast(u8, b[off..].len);
+            const b_slice = b[off..];
+            @memcpy(d.buf[d.buf_len..][0..b_slice.len], b_slice);
+            d.buf_len += @intCast(u8, b_slice.len);
         }
 
         pub fn final(d: *Self, out: *[digest_length]u8) void {
-            mem.set(u8, d.buf[d.buf_len..], 0);
+            @memset(d.buf[d.buf_len..], 0);
             d.t += d.buf_len;
             d.round(d.buf[0..], true);
             for (&d.h) |*x| x.* = mem.nativeToLittle(u32, x.*);
-            mem.copy(u8, out[0..], @ptrCast(*[digest_length]u8, &d.h));
+            out.* = @ptrCast(*[digest_length]u8, &d.h).*;
         }
 
         fn round(d: *Self, b: *const [64]u8, last: bool) void {
@@ -511,7 +512,7 @@ pub fn Blake2b(comptime out_bits: usize) type {
             comptime debug.assert(8 <= out_bits and out_bits <= 512);
 
             var d: Self = undefined;
-            mem.copy(u64, d.h[0..], iv[0..]);
+            d.h = iv;
 
             const key_len = if (options.key) |key| key.len else 0;
             // default parameters
@@ -528,7 +529,7 @@ pub fn Blake2b(comptime out_bits: usize) type {
                 d.h[7] ^= mem.readIntLittle(u64, context[8..16]);
             }
             if (key_len > 0) {
-                mem.set(u8, d.buf[key_len..], 0);
+                @memset(d.buf[key_len..], 0);
                 d.update(options.key.?);
                 d.buf_len = 128;
             }
@@ -547,7 +548,7 @@ pub fn Blake2b(comptime out_bits: usize) type {
             // Partial buffer exists from previous update. Copy into buffer then hash.
             if (d.buf_len != 0 and d.buf_len + b.len > 128) {
                 off += 128 - d.buf_len;
-                mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
+                @memcpy(d.buf[d.buf_len..][0..off], b[0..off]);
                 d.t += 128;
                 d.round(d.buf[0..], false);
                 d.buf_len = 0;
@@ -560,16 +561,17 @@ pub fn Blake2b(comptime out_bits: usize) type {
             }
 
             // Copy any remainder for next pass.
-            mem.copy(u8, d.buf[d.buf_len..], b[off..]);
-            d.buf_len += @intCast(u8, b[off..].len);
+            const b_slice = b[off..];
+            @memcpy(d.buf[d.buf_len..][0..b_slice.len], b_slice);
+            d.buf_len += @intCast(u8, b_slice.len);
         }
 
         pub fn final(d: *Self, out: *[digest_length]u8) void {
-            mem.set(u8, d.buf[d.buf_len..], 0);
+            @memset(d.buf[d.buf_len..], 0);
             d.t += d.buf_len;
             d.round(d.buf[0..], true);
             for (&d.h) |*x| x.* = mem.nativeToLittle(u64, x.*);
-            mem.copy(u8, out[0..], @ptrCast(*[digest_length]u8, &d.h));
+            out.* = @ptrCast(*[digest_length]u8, &d.h).*;
         }
 
         fn round(d: *Self, b: *const [128]u8, last: bool) void {
diff --git a/lib/std/crypto/blake3.zig b/lib/std/crypto/blake3.zig
index 36d717387f..fb580fda13 100644
--- a/lib/std/crypto/blake3.zig
+++ b/lib/std/crypto/blake3.zig
@@ -253,7 +253,7 @@ const Output = struct {
             while (out_word_it.next()) |out_word| {
                 var word_bytes: [4]u8 = undefined;
                 mem.writeIntLittle(u32, &word_bytes, words[word_counter]);
-                mem.copy(u8, out_word, word_bytes[0..out_word.len]);
+                @memcpy(out_word, word_bytes[0..out_word.len]);
                 word_counter += 1;
             }
             output_block_counter += 1;
@@ -284,7 +284,7 @@ const ChunkState = struct {
     fn fillBlockBuf(self: *ChunkState, input: []const u8) []const u8 {
         const want = BLOCK_LEN - self.block_len;
         const take = math.min(want, input.len);
-        mem.copy(u8, self.block[self.block_len..][0..take], input[0..take]);
+        @memcpy(self.block[self.block_len..][0..take], input[0..take]);
         self.block_len += @truncate(u8, take);
         return input[take..];
     }
@@ -336,8 +336,8 @@ fn parentOutput(
     flags: u8,
 ) Output {
     var block_words: [16]u32 align(16) = undefined;
-    mem.copy(u32, block_words[0..8], left_child_cv[0..]);
-    mem.copy(u32, block_words[8..], right_child_cv[0..]);
+    block_words[0..8].* = left_child_cv;
+    block_words[8..].* = right_child_cv;
     return Output{
         .input_chaining_value = key,
         .block_words = block_words,
diff --git a/lib/std/crypto/chacha20.zig b/lib/std/crypto/chacha20.zig
index aa0f148be9..bffc70f500 100644
--- a/lib/std/crypto/chacha20.zig
+++ b/lib/std/crypto/chacha20.zig
@@ -211,7 +211,7 @@ fn ChaChaVecImpl(comptime rounds_nb: usize) type {
 
                 var buf: [64]u8 = undefined;
                 hashToBytes(buf[0..], x);
-                mem.copy(u8, out[i..], buf[0 .. out.len - i]);
+                @memcpy(out[i..], buf[0 .. out.len - i]);
             }
         }
 
@@ -372,7 +372,7 @@ fn ChaChaNonVecImpl(comptime rounds_nb: usize) type {
 
                 var buf: [64]u8 = undefined;
                 hashToBytes(buf[0..], x);
-                mem.copy(u8, out[i..], buf[0 .. out.len - i]);
+                @memcpy(out[i..], buf[0 .. out.len - i]);
             }
         }
 
@@ -413,8 +413,8 @@ fn keyToWords(key: [32]u8) [8]u32 {
 
 fn extend(key: [32]u8, nonce: [24]u8, comptime rounds_nb: usize) struct { key: [32]u8, nonce: [12]u8 } {
     var subnonce: [12]u8 = undefined;
-    mem.set(u8, subnonce[0..4], 0);
-    mem.copy(u8, subnonce[4..], nonce[16..24]);
+    @memset(subnonce[0..4], 0);
+    subnonce[4..].* = nonce[16..24].*;
     return .{
         .key = ChaChaImpl(rounds_nb).hchacha20(nonce[0..16].*, key),
         .nonce = subnonce,
diff --git a/lib/std/crypto/ecdsa.zig b/lib/std/crypto/ecdsa.zig
index 37ae57a7e6..e552af2e26 100644
--- a/lib/std/crypto/ecdsa.zig
+++ b/lib/std/crypto/ecdsa.zig
@@ -102,8 +102,8 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
             /// Return the raw signature (r, s) in big-endian format.
             pub fn toBytes(self: Signature) [encoded_length]u8 {
                 var bytes: [encoded_length]u8 = undefined;
-                mem.copy(u8, bytes[0 .. encoded_length / 2], &self.r);
-                mem.copy(u8, bytes[encoded_length / 2 ..], &self.s);
+                @memcpy(bytes[0 .. encoded_length / 2], &self.r);
+                @memcpy(bytes[encoded_length / 2 ..], &self.s);
                 return bytes;
             }
 
@@ -325,11 +325,11 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
         fn reduceToScalar(comptime unreduced_len: usize, s: [unreduced_len]u8) Curve.scalar.Scalar {
             if (unreduced_len >= 48) {
                 var xs = [_]u8{0} ** 64;
-                mem.copy(u8, xs[xs.len - s.len ..], s[0..]);
+                @memcpy(xs[xs.len - s.len ..], s[0..]);
                 return Curve.scalar.Scalar.fromBytes64(xs, .Big);
             }
             var xs = [_]u8{0} ** 48;
-            mem.copy(u8, xs[xs.len - s.len ..], s[0..]);
+            @memcpy(xs[xs.len - s.len ..], s[0..]);
             return Curve.scalar.Scalar.fromBytes48(xs, .Big);
         }
 
@@ -345,14 +345,13 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
             const m_x = m[m_v.len + 1 + noise_length ..][0..secret_key.len];
             const m_h = m[m.len - h.len ..];
 
-            mem.set(u8, m_v, 0x01);
+            @memset(m_v, 0x01);
             m_i.* = 0x00;
-            if (noise) |n| mem.copy(u8, m_z, &n);
-            mem.copy(u8, m_x, &secret_key);
-            mem.copy(u8, m_h, &h);
+            if (noise) |n| @memcpy(m_z, &n);
+            @memcpy(m_x, &secret_key);
+            @memcpy(m_h, &h);
             Hmac.create(&k, &m, &k);
             Hmac.create(m_v, m_v, &k);
-            mem.copy(u8, m_v, m_v);
             m_i.* = 0x01;
             Hmac.create(&k, &m, &k);
             Hmac.create(m_v, m_v, &k);
@@ -361,10 +360,9 @@ pub fn Ecdsa(comptime Curve: type, comptime Hash: type) type {
                 while (t_off < t.len) : (t_off += m_v.len) {
                     const t_end = @min(t_off + m_v.len, t.len);
                     Hmac.create(m_v, m_v, &k);
-                    std.mem.copy(u8, t[t_off..t_end], m_v[0 .. t_end - t_off]);
+                    @memcpy(t[t_off..t_end], m_v[0 .. t_end - t_off]);
                 }
                 if (Curve.scalar.Scalar.fromBytes(t, .Big)) |s| return s else |_| {}
-                mem.copy(u8, m_v, m_v);
                 m_i.* = 0x00;
                 Hmac.create(&k, m[0 .. m_v.len + 1], &k);
                 Hmac.create(m_v, m_v, &k);
diff --git a/lib/std/crypto/hkdf.zig b/lib/std/crypto/hkdf.zig
index 7102ffe780..9163ba9d15 100644
--- a/lib/std/crypto/hkdf.zig
+++ b/lib/std/crypto/hkdf.zig
@@ -63,7 +63,7 @@ pub fn Hkdf(comptime Hmac: type) type {
                 st.update(&counter);
                 var tmp: [prk_length]u8 = undefined;
                 st.final(tmp[0..prk_length]);
-                mem.copy(u8, out[i..][0..left], tmp[0..left]);
+                @memcpy(out[i..][0..left], tmp[0..left]);
             }
         }
     };
diff --git a/lib/std/crypto/hmac.zig b/lib/std/crypto/hmac.zig
index f279132ee8..8d0daa3032 100644
--- a/lib/std/crypto/hmac.zig
+++ b/lib/std/crypto/hmac.zig
@@ -38,12 +38,12 @@ pub fn Hmac(comptime Hash: type) type {
             // Normalize key length to block size of hash
             if (key.len > Hash.block_length) {
                 Hash.hash(key, scratch[0..mac_length], .{});
-                mem.set(u8, scratch[mac_length..Hash.block_length], 0);
+                @memset(scratch[mac_length..Hash.block_length], 0);
             } else if (key.len < Hash.block_length) {
-                mem.copy(u8, scratch[0..key.len], key);
-                mem.set(u8, scratch[key.len..Hash.block_length], 0);
+                @memcpy(scratch[0..key.len], key);
+                @memset(scratch[key.len..Hash.block_length], 0);
             } else {
-                mem.copy(u8, scratch[0..], key);
+                @memcpy(&scratch, key);
             }
 
             for (&ctx.o_key_pad, 0..) |*b, i| {
diff --git a/lib/std/crypto/isap.zig b/lib/std/crypto/isap.zig
index 0888cfa4dd..5b0da739de 100644
--- a/lib/std/crypto/isap.zig
+++ b/lib/std/crypto/isap.zig
@@ -43,7 +43,7 @@ pub const IsapA128A = struct {
                 }
             } else {
                 var padded = [_]u8{0} ** 8;
-                mem.copy(u8, padded[0..left], m[i..]);
+                @memcpy(padded[0..left], m[i..]);
                 padded[left] = 0x80;
                 isap.st.addBytes(&padded);
                 isap.st.permute();
diff --git a/lib/std/crypto/keccak_p.zig b/lib/std/crypto/keccak_p.zig
index af7c12c8c2..9226f2f6d4 100644
--- a/lib/std/crypto/keccak_p.zig
+++ b/lib/std/crypto/keccak_p.zig
@@ -68,7 +68,7 @@ pub fn KeccakF(comptime f: u11) type {
             }
             if (i < bytes.len) {
                 var padded = [_]u8{0} ** @sizeOf(T);
-                mem.copy(u8, padded[0 .. bytes.len - i], bytes[i..]);
+                @memcpy(padded[0 .. bytes.len - i], bytes[i..]);
                 self.st[i / @sizeOf(T)] = mem.readIntLittle(T, padded[0..]);
             }
         }
@@ -87,7 +87,7 @@ pub fn KeccakF(comptime f: u11) type {
             }
             if (i < bytes.len) {
                 var padded = [_]u8{0} ** @sizeOf(T);
-                mem.copy(u8, padded[0 .. bytes.len - i], bytes[i..]);
+                @memcpy(padded[0 .. bytes.len - i], bytes[i..]);
                 self.st[i / @sizeOf(T)] ^= mem.readIntLittle(T, padded[0..]);
             }
         }
@@ -101,7 +101,7 @@ pub fn KeccakF(comptime f: u11) type {
             if (i < out.len) {
                 var padded = [_]u8{0} ** @sizeOf(T);
                 mem.writeIntLittle(T, padded[0..], self.st[i / @sizeOf(T)]);
-                mem.copy(u8, out[i..], padded[0 .. out.len - i]);
+                @memcpy(out[i..], padded[0 .. out.len - i]);
             }
         }
 
@@ -116,16 +116,16 @@ pub fn KeccakF(comptime f: u11) type {
             }
             if (i < in.len) {
                 var padded = [_]u8{0} ** @sizeOf(T);
-                mem.copy(u8, padded[0 .. in.len - i], in[i..]);
+                @memcpy(padded[0 .. in.len - i], in[i..]);
                 const x = mem.readIntNative(T, &padded) ^ mem.nativeToLittle(T, self.st[i / @sizeOf(T)]);
                 mem.writeIntNative(T, &padded, x);
-                mem.copy(u8, out[i..], padded[0 .. in.len - i]);
+                @memcpy(out[i..], padded[0 .. in.len - i]);
             }
         }
 
         /// Set the words storing the bytes of a given range to zero.
         pub fn clear(self: *Self, from: usize, to: usize) void {
-            mem.set(T, self.st[from / @sizeOf(T) .. (to + @sizeOf(T) - 1) / @sizeOf(T)], 0);
+            @memset(self.st[from / @sizeOf(T) .. (to + @sizeOf(T) - 1) / @sizeOf(T)], 0);
         }
 
         /// Clear the entire state, disabling compiler optimizations.
@@ -215,7 +215,7 @@ pub fn State(comptime f: u11, comptime capacity: u11, comptime delim: u8, compti
             var bytes = bytes_;
             if (self.offset > 0) {
                 const left = math.min(rate - self.offset, bytes.len);
-                mem.copy(u8, self.buf[self.offset..], bytes[0..left]);
+                @memcpy(self.buf[self.offset..][0..left], bytes[0..left]);
                 self.offset += left;
                 if (self.offset == rate) {
                     self.offset = 0;
@@ -231,7 +231,7 @@ pub fn State(comptime f: u11, comptime capacity: u11, comptime delim: u8, compti
                 bytes = bytes[rate..];
             }
             if (bytes.len > 0) {
-                mem.copy(u8, &self.buf, bytes);
+                @memcpy(self.buf[0..bytes.len], bytes);
                 self.offset = bytes.len;
             }
         }
diff --git a/lib/std/crypto/kyber_d00.zig b/lib/std/crypto/kyber_d00.zig
index 21fdb6ff17..b52f9f475d 100644
--- a/lib/std/crypto/kyber_d00.zig
+++ b/lib/std/crypto/kyber_d00.zig
@@ -323,9 +323,9 @@ fn Kyber(comptime p: Params) type {
                 s += InnerSk.bytes_length;
                 ret.pk = InnerPk.fromBytes(buf[s .. s + InnerPk.bytes_length]);
                 s += InnerPk.bytes_length;
-                mem.copy(u8, &ret.hpk, buf[s .. s + h_length]);
+                ret.hpk = buf[s..][0..h_length].*;
                 s += h_length;
-                mem.copy(u8, &ret.z, buf[s .. s + shared_length]);
+                ret.z = buf[s..][0..shared_length].*;
                 return ret;
             }
         };
@@ -345,7 +345,7 @@ fn Kyber(comptime p: Params) type {
                     break :sk random_seed;
                 };
                 var ret: KeyPair = undefined;
-                mem.copy(u8, &ret.secret_key.z, seed[inner_seed_length..seed_length]);
+                ret.secret_key.z = seed[inner_seed_length..seed_length].*;
 
                 // Generate inner key
                 innerKeyFromSeed(
@@ -356,7 +356,7 @@ fn Kyber(comptime p: Params) type {
                 ret.secret_key.pk = ret.public_key.pk;
 
                 // Copy over z from seed.
-                mem.copy(u8, &ret.secret_key.z, seed[inner_seed_length..seed_length]);
+                ret.secret_key.z = seed[inner_seed_length..seed_length].*;
 
                 // Compute H(pk)
                 var h = sha3.Sha3_256.init(.{});
@@ -418,7 +418,7 @@ fn Kyber(comptime p: Params) type {
             fn fromBytes(buf: *const [bytes_length]u8) InnerPk {
                 var ret: InnerPk = undefined;
                 ret.th = V.fromBytes(buf[0..V.bytes_length]).normalize();
-                mem.copy(u8, &ret.rho, buf[V.bytes_length..bytes_length]);
+                ret.rho = buf[V.bytes_length..bytes_length].*;
                 ret.aT = M.uniform(ret.rho, true);
                 return ret;
             }
@@ -459,7 +459,7 @@ fn Kyber(comptime p: Params) type {
             var h = sha3.Sha3_512.init(.{});
             h.update(&seed);
             h.final(&expanded_seed);
-            mem.copy(u8, &pk.rho, expanded_seed[0..32]);
+            pk.rho = expanded_seed[0..32].*;
             const sigma = expanded_seed[32..64];
             pk.aT = M.uniform(pk.rho, false); // Expand ρ to A; we'll transpose later on
 
@@ -1381,7 +1381,7 @@ fn Vec(comptime K: u8) type {
             const cs = comptime Poly.compressedSize(d);
             var ret: [compressedSize(d)]u8 = undefined;
             inline for (0..K) |i| {
-                mem.copy(u8, ret[i * cs .. (i + 1) * cs], &v.ps[i].compress(d));
+                ret[i * cs .. (i + 1) * cs].* = v.ps[i].compress(d);
             }
             return ret;
         }
@@ -1399,11 +1399,7 @@ fn Vec(comptime K: u8) type {
         fn toBytes(v: Self) [bytes_length]u8 {
             var ret: [bytes_length]u8 = undefined;
             inline for (0..K) |i| {
-                mem.copy(
-                    u8,
-                    ret[i * Poly.bytes_length .. (i + 1) * Poly.bytes_length],
-                    &v.ps[i].toBytes(),
-                );
+                ret[i * Poly.bytes_length .. (i + 1) * Poly.bytes_length].* = v.ps[i].toBytes();
             }
             return ret;
         }
@@ -1479,7 +1475,7 @@ test "MulHat" {
         const p2 = a.ntt().mulHat(b.ntt()).barrettReduce().invNTT().normalize();
         var p: Poly = undefined;
 
-        mem.set(i16, &p.cs, 0);
+        @memset(&p.cs, 0);
 
         for (0..N) |i| {
             for (0..N) |j| {
@@ -1742,15 +1738,15 @@ const NistDRBG = struct {
             g.incV();
             var block: [16]u8 = undefined;
             ctx.encrypt(&block, &g.v);
-            mem.copy(u8, buf[i * 16 .. (i + 1) * 16], &block);
+            buf[i * 16 ..][0..16].* = block;
         }
         if (pd) |p| {
             for (&buf, p) |*b, x| {
                 b.* ^= x;
             }
         }
-        mem.copy(u8, &g.key, buf[0..32]);
-        mem.copy(u8, &g.v, buf[32..48]);
+        g.key = buf[0..32].*;
+        g.v = buf[32..48].*;
     }
 
     // randombytes.
@@ -1763,10 +1759,10 @@ const NistDRBG = struct {
             g.incV();
             ctx.encrypt(&block, &g.v);
             if (dst.len < 16) {
-                mem.copy(u8, dst, block[0..dst.len]);
+                @memcpy(dst, block[0..dst.len]);
                 break;
             }
-            mem.copy(u8, dst, &block);
+            dst[0..block.len].* = block;
             dst = dst[16..dst.len];
         }
         g.update(null);
diff --git a/lib/std/crypto/md5.zig b/lib/std/crypto/md5.zig
index 6276fadb43..bd4a78c032 100644
--- a/lib/std/crypto/md5.zig
+++ b/lib/std/crypto/md5.zig
@@ -66,7 +66,7 @@ pub const Md5 = struct {
         // Partial buffer exists from previous update. Copy into buffer then hash.
         if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
             off += 64 - d.buf_len;
-            mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
+            @memcpy(d.buf[d.buf_len..][0..off], b[0..off]);
 
             d.round(&d.buf);
             d.buf_len = 0;
@@ -78,8 +78,9 @@ pub const Md5 = struct {
         }
 
         // Copy any remainder for next pass.
-        mem.copy(u8, d.buf[d.buf_len..], b[off..]);
-        d.buf_len += @intCast(u8, b[off..].len);
+        const b_slice = b[off..];
+        @memcpy(d.buf[d.buf_len..][0..b_slice.len], b_slice);
+        d.buf_len += @intCast(u8, b_slice.len);
 
         // Md5 uses the bottom 64-bits for length padding
         d.total_len +%= b.len;
@@ -87,7 +88,7 @@ pub const Md5 = struct {
 
     pub fn final(d: *Self, out: *[digest_length]u8) void {
         // The buffer here will never be completely full.
-        mem.set(u8, d.buf[d.buf_len..], 0);
+        @memset(d.buf[d.buf_len..], 0);
 
         // Append padding bits.
         d.buf[d.buf_len] = 0x80;
@@ -96,7 +97,7 @@ pub const Md5 = struct {
         // > 448 mod 512 so need to add an extra round to wrap around.
         if (64 - d.buf_len < 8) {
             d.round(d.buf[0..]);
-            mem.set(u8, d.buf[0..], 0);
+            @memset(d.buf[0..], 0);
         }
 
         // Append message length.
diff --git a/lib/std/crypto/modes.zig b/lib/std/crypto/modes.zig
index 325d8c0ceb..eed803a899 100644
--- a/lib/std/crypto/modes.zig
+++ b/lib/std/crypto/modes.zig
@@ -38,8 +38,10 @@ pub fn ctr(comptime BlockCipher: anytype, block_cipher: BlockCipher, dst: []u8,
     if (i < src.len) {
         mem.writeInt(u128, &counter, counterInt, endian);
         var pad = [_]u8{0} ** block_length;
-        mem.copy(u8, &pad, src[i..]);
+        const src_slice = src[i..];
+        @memcpy(pad[0..src_slice.len], src_slice);
         block_cipher.xor(&pad, &pad, counter);
-        mem.copy(u8, dst[i..], pad[0 .. src.len - i]);
+        const pad_slice = pad[0 .. src.len - i];
+        @memcpy(dst[i..][0..pad_slice.len], pad_slice);
     }
 }
diff --git a/lib/std/crypto/pbkdf2.zig b/lib/std/crypto/pbkdf2.zig
index 6f9783df72..7c6df5444d 100644
--- a/lib/std/crypto/pbkdf2.zig
+++ b/lib/std/crypto/pbkdf2.zig
@@ -129,13 +129,13 @@ pub fn pbkdf2(dk: []u8, password: []const u8, salt: []const u8, rounds: u32, com
         const offset = block * h_len;
         const block_len = if (block != blocks_count - 1) h_len else r;
         const dk_block: []u8 = dk[offset..][0..block_len];
-        mem.copy(u8, dk_block, prev_block[0..dk_block.len]);
+        @memcpy(dk_block, prev_block[0..dk_block.len]);
 
         var i: u32 = 1;
         while (i < rounds) : (i += 1) {
             // U_c = PRF (P, U_{c-1})
             Prf.create(&new_block, prev_block[0..], password);
-            mem.copy(u8, prev_block[0..], new_block[0..]);
+            prev_block = new_block;
 
             // F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
             for (dk_block, 0..) |_, j| {
diff --git a/lib/std/crypto/pcurves/common.zig b/lib/std/crypto/pcurves/common.zig
index 40f4a728c7..5d41bc190a 100644
--- a/lib/std/crypto/pcurves/common.zig
+++ b/lib/std/crypto/pcurves/common.zig
@@ -228,8 +228,8 @@ pub fn Field(comptime params: FieldParams) type {
             }
             if (iterations % 2 != 0) {
                 fiat.divstep(&out1, &out2, &out3, &out4, &out5, d, f, g, v, r);
-                mem.copy(Word, &v, &out4);
-                mem.copy(Word, &f, &out2);
+                v = out4;
+                f = out2;
             }
             var v_opp: Limbs = undefined;
             fiat.opp(&v_opp, v);
diff --git a/lib/std/crypto/pcurves/p256.zig b/lib/std/crypto/pcurves/p256.zig
index a160d08016..0460515511 100644
--- a/lib/std/crypto/pcurves/p256.zig
+++ b/lib/std/crypto/pcurves/p256.zig
@@ -105,7 +105,7 @@ pub const P256 = struct {
         var out: [33]u8 = undefined;
         const xy = p.affineCoordinates();
         out[0] = if (xy.y.isOdd()) 3 else 2;
-        mem.copy(u8, out[1..], &xy.x.toBytes(.Big));
+        out[1..].* = xy.x.toBytes(.Big);
         return out;
     }
 
@@ -114,8 +114,8 @@ pub const P256 = struct {
         var out: [65]u8 = undefined;
         out[0] = 4;
         const xy = p.affineCoordinates();
-        mem.copy(u8, out[1..33], &xy.x.toBytes(.Big));
-        mem.copy(u8, out[33..65], &xy.y.toBytes(.Big));
+        out[1..33].* = xy.x.toBytes(.Big);
+        out[33..65].* = xy.y.toBytes(.Big);
         return out;
     }
 
diff --git a/lib/std/crypto/pcurves/p256/scalar.zig b/lib/std/crypto/pcurves/p256/scalar.zig
index ce019082ef..4e88d1fee7 100644
--- a/lib/std/crypto/pcurves/p256/scalar.zig
+++ b/lib/std/crypto/pcurves/p256/scalar.zig
@@ -192,20 +192,20 @@ const ScalarDouble = struct {
         var t = ScalarDouble{ .x1 = undefined, .x2 = Fe.zero, .x3 = Fe.zero };
         {
             var b = [_]u8{0} ** encoded_length;
-            const len = math.min(s.len, 24);
-            mem.copy(u8, b[0..len], s[0..len]);
+            const len = @min(s.len, 24);
+            b[0..len].* = s[0..len].*;
             t.x1 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         if (s_.len >= 24) {
             var b = [_]u8{0} ** encoded_length;
-            const len = math.min(s.len - 24, 24);
-            mem.copy(u8, b[0..len], s[24..][0..len]);
+            const len = @min(s.len - 24, 24);
+            b[0..len].* = s[24..][0..len].*;
             t.x2 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         if (s_.len >= 48) {
             var b = [_]u8{0} ** encoded_length;
             const len = s.len - 48;
-            mem.copy(u8, b[0..len], s[48..][0..len]);
+            b[0..len].* = s[48..][0..len].*;
             t.x3 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         return t;
diff --git a/lib/std/crypto/pcurves/p384.zig b/lib/std/crypto/pcurves/p384.zig
index 3aaf9e341f..6662fc0011 100644
--- a/lib/std/crypto/pcurves/p384.zig
+++ b/lib/std/crypto/pcurves/p384.zig
@@ -105,7 +105,7 @@ pub const P384 = struct {
         var out: [49]u8 = undefined;
         const xy = p.affineCoordinates();
         out[0] = if (xy.y.isOdd()) 3 else 2;
-        mem.copy(u8, out[1..], &xy.x.toBytes(.Big));
+        out[1..].* = xy.x.toBytes(.Big);
         return out;
     }
 
@@ -114,8 +114,8 @@ pub const P384 = struct {
         var out: [97]u8 = undefined;
         out[0] = 4;
         const xy = p.affineCoordinates();
-        mem.copy(u8, out[1..49], &xy.x.toBytes(.Big));
-        mem.copy(u8, out[49..97], &xy.y.toBytes(.Big));
+        out[1..49].* = xy.x.toBytes(.Big);
+        out[49..97].* = xy.y.toBytes(.Big);
         return out;
     }
 
diff --git a/lib/std/crypto/pcurves/p384/scalar.zig b/lib/std/crypto/pcurves/p384/scalar.zig
index ec71a52efa..ef257ab7ce 100644
--- a/lib/std/crypto/pcurves/p384/scalar.zig
+++ b/lib/std/crypto/pcurves/p384/scalar.zig
@@ -180,14 +180,14 @@ const ScalarDouble = struct {
         var t = ScalarDouble{ .x1 = undefined, .x2 = Fe.zero };
         {
             var b = [_]u8{0} ** encoded_length;
-            const len = math.min(s.len, 32);
-            mem.copy(u8, b[0..len], s[0..len]);
+            const len = @min(s.len, 32);
+            b[0..len].* = s[0..len].*;
             t.x1 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         if (s_.len >= 32) {
             var b = [_]u8{0} ** encoded_length;
-            const len = math.min(s.len - 32, 32);
-            mem.copy(u8, b[0..len], s[32..][0..len]);
+            const len = @min(s.len - 32, 32);
+            b[0..len].* = s[32..][0..len].*;
             t.x2 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         return t;
diff --git a/lib/std/crypto/pcurves/secp256k1.zig b/lib/std/crypto/pcurves/secp256k1.zig
index 6998b0db82..753f929f44 100644
--- a/lib/std/crypto/pcurves/secp256k1.zig
+++ b/lib/std/crypto/pcurves/secp256k1.zig
@@ -158,7 +158,7 @@ pub const Secp256k1 = struct {
         var out: [33]u8 = undefined;
         const xy = p.affineCoordinates();
         out[0] = if (xy.y.isOdd()) 3 else 2;
-        mem.copy(u8, out[1..], &xy.x.toBytes(.Big));
+        out[1..].* = xy.x.toBytes(.Big);
         return out;
     }
 
@@ -167,8 +167,8 @@ pub const Secp256k1 = struct {
         var out: [65]u8 = undefined;
         out[0] = 4;
         const xy = p.affineCoordinates();
-        mem.copy(u8, out[1..33], &xy.x.toBytes(.Big));
-        mem.copy(u8, out[33..65], &xy.y.toBytes(.Big));
+        out[1..33].* = xy.x.toBytes(.Big);
+        out[33..65].* = xy.y.toBytes(.Big);
         return out;
     }
 
diff --git a/lib/std/crypto/pcurves/secp256k1/scalar.zig b/lib/std/crypto/pcurves/secp256k1/scalar.zig
index 0b7d6e952d..e0b5e053e3 100644
--- a/lib/std/crypto/pcurves/secp256k1/scalar.zig
+++ b/lib/std/crypto/pcurves/secp256k1/scalar.zig
@@ -192,20 +192,20 @@ const ScalarDouble = struct {
         var t = ScalarDouble{ .x1 = undefined, .x2 = Fe.zero, .x3 = Fe.zero };
         {
             var b = [_]u8{0} ** encoded_length;
-            const len = math.min(s.len, 24);
-            mem.copy(u8, b[0..len], s[0..len]);
+            const len = @min(s.len, 24);
+            b[0..len].* = s[0..len].*;
             t.x1 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         if (s_.len >= 24) {
             var b = [_]u8{0} ** encoded_length;
-            const len = math.min(s.len - 24, 24);
-            mem.copy(u8, b[0..len], s[24..][0..len]);
+            const len = @min(s.len - 24, 24);
+            b[0..len].* = s[24..][0..len].*;
             t.x2 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         if (s_.len >= 48) {
             var b = [_]u8{0} ** encoded_length;
             const len = s.len - 48;
-            mem.copy(u8, b[0..len], s[48..][0..len]);
+            b[0..len].* = s[48..][0..len].*;
             t.x3 = Fe.fromBytes(b, .Little) catch unreachable;
         }
         return t;
diff --git a/lib/std/crypto/phc_encoding.zig b/lib/std/crypto/phc_encoding.zig
index 4b6965d040..cc0f10e395 100644
--- a/lib/std/crypto/phc_encoding.zig
+++ b/lib/std/crypto/phc_encoding.zig
@@ -35,7 +35,7 @@ pub fn BinValue(comptime max_len: usize) type {
         pub fn fromSlice(slice: []const u8) Error!Self {
             if (slice.len > capacity) return Error.NoSpaceLeft;
             var bin_value: Self = undefined;
-            mem.copy(u8, &bin_value.buf, slice);
+            @memcpy(bin_value.buf[0..slice.len], slice);
             bin_value.len = slice.len;
             return bin_value;
         }
diff --git a/lib/std/crypto/salsa20.zig b/lib/std/crypto/salsa20.zig
index 492b8e9988..7f57e6cecb 100644
--- a/lib/std/crypto/salsa20.zig
+++ b/lib/std/crypto/salsa20.zig
@@ -383,10 +383,10 @@ pub const XSalsa20Poly1305 = struct {
         debug.assert(c.len == m.len);
         const extended = extend(rounds, k, npub);
         var block0 = [_]u8{0} ** 64;
-        const mlen0 = math.min(32, m.len);
-        mem.copy(u8, block0[32..][0..mlen0], m[0..mlen0]);
+        const mlen0 = @min(32, m.len);
+        @memcpy(block0[32..][0..mlen0], m[0..mlen0]);
         Salsa20.xor(block0[0..], block0[0..], 0, extended.key, extended.nonce);
-        mem.copy(u8, c[0..mlen0], block0[32..][0..mlen0]);
+        @memcpy(c[0..mlen0], block0[32..][0..mlen0]);
         Salsa20.xor(c[mlen0..], m[mlen0..], 1, extended.key, extended.nonce);
         var mac = Poly1305.init(block0[0..32]);
         mac.update(ad);
@@ -405,7 +405,7 @@ pub const XSalsa20Poly1305 = struct {
         const extended = extend(rounds, k, npub);
         var block0 = [_]u8{0} ** 64;
         const mlen0 = math.min(32, c.len);
-        mem.copy(u8, block0[32..][0..mlen0], c[0..mlen0]);
+        @memcpy(block0[32..][0..mlen0], c[0..mlen0]);
         Salsa20.xor(block0[0..], block0[0..], 0, extended.key, extended.nonce);
         var mac = Poly1305.init(block0[0..32]);
         mac.update(ad);
@@ -420,7 +420,7 @@ pub const XSalsa20Poly1305 = struct {
             utils.secureZero(u8, &computedTag);
             return error.AuthenticationFailed;
         }
-        mem.copy(u8, m[0..mlen0], block0[32..][0..mlen0]);
+        @memcpy(m[0..mlen0], block0[32..][0..mlen0]);
         Salsa20.xor(m[mlen0..], c[mlen0..], 1, extended.key, extended.nonce);
     }
 };
@@ -533,7 +533,7 @@ pub const SealedBox = struct {
         debug.assert(c.len == m.len + seal_length);
         var ekp = try KeyPair.create(null);
         const nonce = createNonce(ekp.public_key, public_key);
-        mem.copy(u8, c[0..public_length], ekp.public_key[0..]);
+        c[0..public_length].* = ekp.public_key;
         try Box.seal(c[Box.public_length..], m, nonce, public_key, ekp.secret_key);
         utils.secureZero(u8, ekp.secret_key[0..]);
     }
diff --git a/lib/std/crypto/scrypt.zig b/lib/std/crypto/scrypt.zig
index dc73d974c7..077de3b510 100644
--- a/lib/std/crypto/scrypt.zig
+++ b/lib/std/crypto/scrypt.zig
@@ -27,7 +27,7 @@ const max_salt_len = 64;
 const max_hash_len = 64;
 
 fn blockCopy(dst: []align(16) u32, src: []align(16) const u32, n: usize) void {
-    mem.copy(u32, dst, src[0 .. n * 16]);
+    @memcpy(dst[0 .. n * 16], src[0 .. n * 16]);
 }
 
 fn blockXor(dst: []align(16) u32, src: []align(16) const u32, n: usize) void {
@@ -242,7 +242,7 @@ const crypt_format = struct {
             pub fn fromSlice(slice: []const u8) EncodingError!Self {
                 if (slice.len > capacity) return EncodingError.NoSpaceLeft;
                 var bin_value: Self = undefined;
-                mem.copy(u8, &bin_value.buf, slice);
+                @memcpy(bin_value.buf[0..slice.len], slice);
                 bin_value.len = slice.len;
                 return bin_value;
             }
@@ -314,7 +314,7 @@ const crypt_format = struct {
 
     fn serializeTo(params: anytype, out: anytype) !void {
         var header: [14]u8 = undefined;
-        mem.copy(u8, header[0..3], prefix);
+        header[0..3].* = prefix.*;
         Codec.intEncode(header[3..4], params.ln);
         Codec.intEncode(header[4..9], params.r);
         Codec.intEncode(header[9..14], params.p);
diff --git a/lib/std/crypto/sha1.zig b/lib/std/crypto/sha1.zig
index 4d11b04eb5..1f5f3eaae2 100644
--- a/lib/std/crypto/sha1.zig
+++ b/lib/std/crypto/sha1.zig
@@ -62,7 +62,7 @@ pub const Sha1 = struct {
         // Partial buffer exists from previous update. Copy into buffer then hash.
         if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
             off += 64 - d.buf_len;
-            mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
+            @memcpy(d.buf[d.buf_len..][0..off], b[0..off]);
 
             d.round(d.buf[0..]);
             d.buf_len = 0;
@@ -74,7 +74,7 @@ pub const Sha1 = struct {
         }
 
         // Copy any remainder for next pass.
-        mem.copy(u8, d.buf[d.buf_len..], b[off..]);
+        @memcpy(d.buf[d.buf_len..][0 .. b.len - off], b[off..]);
         d.buf_len += @intCast(u8, b[off..].len);
 
         d.total_len += b.len;
@@ -82,7 +82,7 @@ pub const Sha1 = struct {
 
     pub fn final(d: *Self, out: *[digest_length]u8) void {
         // The buffer here will never be completely full.
-        mem.set(u8, d.buf[d.buf_len..], 0);
+        @memset(d.buf[d.buf_len..], 0);
 
         // Append padding bits.
         d.buf[d.buf_len] = 0x80;
@@ -91,7 +91,7 @@ pub const Sha1 = struct {
         // > 448 mod 512 so need to add an extra round to wrap around.
         if (64 - d.buf_len < 8) {
             d.round(d.buf[0..]);
-            mem.set(u8, d.buf[0..], 0);
+            @memset(d.buf[0..], 0);
         }
 
         // Append message length.
diff --git a/lib/std/crypto/sha2.zig b/lib/std/crypto/sha2.zig
index ad99079852..bd5a7cc5d4 100644
--- a/lib/std/crypto/sha2.zig
+++ b/lib/std/crypto/sha2.zig
@@ -118,7 +118,7 @@ fn Sha2x32(comptime params: Sha2Params32) type {
             // Partial buffer exists from previous update. Copy into buffer then hash.
             if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
                 off += 64 - d.buf_len;
-                mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
+                @memcpy(d.buf[d.buf_len..][0..off], b[0..off]);
 
                 d.round(&d.buf);
                 d.buf_len = 0;
@@ -130,7 +130,8 @@ fn Sha2x32(comptime params: Sha2Params32) type {
             }
 
             // Copy any remainder for next pass.
-            mem.copy(u8, d.buf[d.buf_len..], b[off..]);
+            const b_slice = b[off..];
+            @memcpy(d.buf[d.buf_len..][0..b_slice.len], b_slice);
             d.buf_len += @intCast(u8, b[off..].len);
 
             d.total_len += b.len;
@@ -143,7 +144,7 @@ fn Sha2x32(comptime params: Sha2Params32) type {
 
         pub fn final(d: *Self, out: *[digest_length]u8) void {
             // The buffer here will never be completely full.
-            mem.set(u8, d.buf[d.buf_len..], 0);
+            @memset(d.buf[d.buf_len..], 0);
 
             // Append padding bits.
             d.buf[d.buf_len] = 0x80;
@@ -152,7 +153,7 @@ fn Sha2x32(comptime params: Sha2Params32) type {
             // > 448 mod 512 so need to add an extra round to wrap around.
             if (64 - d.buf_len < 8) {
                 d.round(&d.buf);
-                mem.set(u8, d.buf[0..], 0);
+                @memset(d.buf[0..], 0);
             }
 
             // Append message length.
@@ -609,7 +610,7 @@ fn Sha2x64(comptime params: Sha2Params64) type {
             // Partial buffer exists from previous update. Copy into buffer then hash.
             if (d.buf_len != 0 and d.buf_len + b.len >= 128) {
                 off += 128 - d.buf_len;
-                mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
+                @memcpy(d.buf[d.buf_len..][0..off], b[0..off]);
 
                 d.round(&d.buf);
                 d.buf_len = 0;
@@ -621,7 +622,8 @@ fn Sha2x64(comptime params: Sha2Params64) type {
             }
 
             // Copy any remainder for next pass.
-            mem.copy(u8, d.buf[d.buf_len..], b[off..]);
+            const b_slice = b[off..];
+            @memcpy(d.buf[d.buf_len..][0..b_slice.len], b_slice);
             d.buf_len += @intCast(u8, b[off..].len);
 
             d.total_len += b.len;
@@ -634,7 +636,7 @@ fn Sha2x64(comptime params: Sha2Params64) type {
 
         pub fn final(d: *Self, out: *[digest_length]u8) void {
             // The buffer here will never be completely full.
-            mem.set(u8, d.buf[d.buf_len..], 0);
+            @memset(d.buf[d.buf_len..], 0);
 
             // Append padding bits.
             d.buf[d.buf_len] = 0x80;
@@ -643,7 +645,7 @@ fn Sha2x64(comptime params: Sha2Params64) type {
             // > 896 mod 1024 so need to add an extra round to wrap around.
             if (128 - d.buf_len < 16) {
                 d.round(d.buf[0..]);
-                mem.set(u8, d.buf[0..], 0);
+                @memset(d.buf[0..], 0);
             }
 
             // Append message length.
diff --git a/lib/std/crypto/sha3.zig b/lib/std/crypto/sha3.zig
index 1f48f87c53..23f9e65534 100644
--- a/lib/std/crypto/sha3.zig
+++ b/lib/std/crypto/sha3.zig
@@ -149,7 +149,7 @@ fn ShakeLike(comptime security_level: u11, comptime delim: u8, comptime rounds:
                 const left = self.buf.len - self.offset;
                 if (left > 0) {
                     const n = math.min(left, out.len);
-                    mem.copy(u8, out[0..n], self.buf[self.offset..][0..n]);
+                    @memcpy(out[0..n], self.buf[self.offset..][0..n]);
                     out = out[n..];
                     self.offset += n;
                     if (out.len == 0) {
@@ -164,7 +164,7 @@ fn ShakeLike(comptime security_level: u11, comptime delim: u8, comptime rounds:
             }
             if (out.len > 0) {
                 self.st.squeeze(self.buf[0..]);
-                mem.copy(u8, out[0..], self.buf[0..out.len]);
+                @memcpy(out[0..], self.buf[0..out.len]);
                 self.offset = out.len;
             }
         }
diff --git a/lib/std/crypto/siphash.zig b/lib/std/crypto/siphash.zig
index 16388439d1..d91485cdfa 100644
--- a/lib/std/crypto/siphash.zig
+++ b/lib/std/crypto/siphash.zig
@@ -98,7 +98,7 @@ fn SipHashStateless(comptime T: type, comptime c_rounds: usize, comptime d_round
             self.msg_len +%= @truncate(u8, b.len);
 
             var buf = [_]u8{0} ** 8;
-            mem.copy(u8, buf[0..], b[0..]);
+            @memcpy(buf[0..b.len], b);
             buf[7] = self.msg_len;
             self.round(buf);
 
@@ -203,7 +203,7 @@ fn SipHash(comptime T: type, comptime c_rounds: usize, comptime d_rounds: usize)
 
             if (self.buf_len != 0 and self.buf_len + b.len >= 8) {
                 off += 8 - self.buf_len;
-                mem.copy(u8, self.buf[self.buf_len..], b[0..off]);
+                @memcpy(self.buf[self.buf_len..][0..off], b[0..off]);
                 self.state.update(self.buf[0..]);
                 self.buf_len = 0;
             }
@@ -212,8 +212,9 @@ fn SipHash(comptime T: type, comptime c_rounds: usize, comptime d_rounds: usize)
             const aligned_len = remain_len - (remain_len % 8);
             self.state.update(b[off .. off + aligned_len]);
 
-            mem.copy(u8, self.buf[self.buf_len..], b[off + aligned_len ..]);
-            self.buf_len += @intCast(u8, b[off + aligned_len ..].len);
+            const b_slice = b[off + aligned_len ..];
+            @memcpy(self.buf[self.buf_len..][0..b_slice.len], b_slice);
+            self.buf_len += @intCast(u8, b_slice.len);
         }
 
         pub fn peek(self: Self) [mac_length]u8 {
diff --git a/lib/std/crypto/tls.zig b/lib/std/crypto/tls.zig
index 5b5d3dea67..8ae494edce 100644
--- a/lib/std/crypto/tls.zig
+++ b/lib/std/crypto/tls.zig
@@ -312,11 +312,11 @@ pub fn hkdfExpandLabel(
     buf[2] = @intCast(u8, tls13.len + label.len);
     buf[3..][0..tls13.len].* = tls13.*;
     var i: usize = 3 + tls13.len;
-    mem.copy(u8, buf[i..], label);
+    @memcpy(buf[i..][0..label.len], label);
     i += label.len;
     buf[i] = @intCast(u8, context.len);
     i += 1;
-    mem.copy(u8, buf[i..], context);
+    @memcpy(buf[i..][0..context.len], context);
     i += context.len;
 
     var result: [len]u8 = undefined;
diff --git a/lib/std/crypto/tls/Client.zig b/lib/std/crypto/tls/Client.zig
index 1d94dfce31..c886bc7276 100644
--- a/lib/std/crypto/tls/Client.zig
+++ b/lib/std/crypto/tls/Client.zig
@@ -685,7 +685,7 @@ pub fn init(stream: anytype, ca_bundle: Certificate.Bundle, host: []const u8) In
                                 .application_cipher = app_cipher,
                                 .partially_read_buffer = undefined,
                             };
-                            mem.copy(u8, &client.partially_read_buffer, leftover);
+                            @memcpy(client.partially_read_buffer[0..leftover.len], leftover);
                             return client;
                         },
                         else => {
@@ -809,7 +809,7 @@ fn prepareCiphertextRecord(
                     .overhead_len = overhead_len,
                 };
 
-                mem.copy(u8, &cleartext_buf, bytes[bytes_i..][0..encrypted_content_len]);
+                @memcpy(cleartext_buf[0..encrypted_content_len], bytes[bytes_i..][0..encrypted_content_len]);
                 cleartext_buf[encrypted_content_len] = @enumToInt(inner_content_type);
                 bytes_i += encrypted_content_len;
                 const ciphertext_len = encrypted_content_len + 1;
@@ -1029,8 +1029,8 @@ pub fn readvAdvanced(c: *Client, stream: anytype, iovecs: []const std.os.iovec)
             if (frag1.len < second_len)
                 return finishRead2(c, first, frag1, vp.total);
 
-            mem.copy(u8, frag[0..in], first);
-            mem.copy(u8, frag[first.len..], frag1[0..second_len]);
+            @memcpy(frag[0..in], first);
+            @memcpy(frag[first.len..][0..second_len], frag1[0..second_len]);
             frag = frag[0..full_record_len];
             frag1 = frag1[second_len..];
             in = 0;
@@ -1059,8 +1059,8 @@ pub fn readvAdvanced(c: *Client, stream: anytype, iovecs: []const std.os.iovec)
             if (frag1.len < second_len)
                 return finishRead2(c, first, frag1, vp.total);
 
-            mem.copy(u8, frag[0..in], first);
-            mem.copy(u8, frag[first.len..], frag1[0..second_len]);
+            @memcpy(frag[0..in], first);
+            @memcpy(frag[first.len..][0..second_len], frag1[0..second_len]);
             frag = frag[0..full_record_len];
             frag1 = frag1[second_len..];
             in = 0;
@@ -1177,7 +1177,7 @@ pub fn readvAdvanced(c: *Client, stream: anytype, iovecs: []const std.os.iovec)
                                 // We have already run out of room in iovecs. Continue
                                 // appending to `partially_read_buffer`.
                                 const dest = c.partially_read_buffer[c.partial_ciphertext_idx..];
-                                mem.copy(u8, dest, msg);
+                                @memcpy(dest[0..msg.len], msg);
                                 c.partial_ciphertext_idx = @intCast(@TypeOf(c.partial_ciphertext_idx), c.partial_ciphertext_idx + msg.len);
                             } else {
                                 const amt = vp.put(msg);
@@ -1185,7 +1185,7 @@ pub fn readvAdvanced(c: *Client, stream: anytype, iovecs: []const std.os.iovec)
                                     const rest = msg[amt..];
                                     c.partial_cleartext_idx = 0;
                                     c.partial_ciphertext_idx = @intCast(@TypeOf(c.partial_ciphertext_idx), rest.len);
-                                    mem.copy(u8, &c.partially_read_buffer, rest);
+                                    @memcpy(c.partially_read_buffer[0..rest.len], rest);
                                 }
                             }
                         } else {
@@ -1213,12 +1213,12 @@ fn finishRead(c: *Client, frag: []const u8, in: usize, out: usize) usize {
     if (c.partial_ciphertext_idx > c.partial_cleartext_idx) {
         // There is cleartext at the beginning already which we need to preserve.
         c.partial_ciphertext_end = @intCast(@TypeOf(c.partial_ciphertext_end), c.partial_ciphertext_idx + saved_buf.len);
-        mem.copy(u8, c.partially_read_buffer[c.partial_ciphertext_idx..], saved_buf);
+        @memcpy(c.partially_read_buffer[c.partial_ciphertext_idx..][0..saved_buf.len], saved_buf);
     } else {
         c.partial_cleartext_idx = 0;
         c.partial_ciphertext_idx = 0;
         c.partial_ciphertext_end = @intCast(@TypeOf(c.partial_ciphertext_end), saved_buf.len);
-        mem.copy(u8, &c.partially_read_buffer, saved_buf);
+        @memcpy(c.partially_read_buffer[0..saved_buf.len], saved_buf);
     }
     return out;
 }
@@ -1227,14 +1227,14 @@ fn finishRead2(c: *Client, first: []const u8, frag1: []const u8, out: usize) usi
     if (c.partial_ciphertext_idx > c.partial_cleartext_idx) {
         // There is cleartext at the beginning already which we need to preserve.
         c.partial_ciphertext_end = @intCast(@TypeOf(c.partial_ciphertext_end), c.partial_ciphertext_idx + first.len + frag1.len);
-        mem.copy(u8, c.partially_read_buffer[c.partial_ciphertext_idx..], first);
-        mem.copy(u8, c.partially_read_buffer[c.partial_ciphertext_idx + first.len ..], frag1);
+        @memcpy(c.partially_read_buffer[c.partial_ciphertext_idx..][0..first.len], first);
+        @memcpy(c.partially_read_buffer[c.partial_ciphertext_idx + first.len ..][0..frag1.len], frag1);
     } else {
         c.partial_cleartext_idx = 0;
         c.partial_ciphertext_idx = 0;
         c.partial_ciphertext_end = @intCast(@TypeOf(c.partial_ciphertext_end), first.len + frag1.len);
-        mem.copy(u8, &c.partially_read_buffer, first);
-        mem.copy(u8, c.partially_read_buffer[first.len..], frag1);
+        @memcpy(c.partially_read_buffer[0..first.len], first);
+        @memcpy(c.partially_read_buffer[first.len..][0..frag1.len], frag1);
     }
     return out;
 }
@@ -1282,7 +1282,7 @@ const VecPut = struct {
             const v = vp.iovecs[vp.idx];
             const dest = v.iov_base[vp.off..v.iov_len];
             const src = bytes[bytes_i..][0..@min(dest.len, bytes.len - bytes_i)];
-            mem.copy(u8, dest, src);
+            @memcpy(dest[0..src.len], src);
             bytes_i += src.len;
             vp.off += src.len;
             if (vp.off >= v.iov_len) {
diff --git a/lib/std/crypto/utils.zig b/lib/std/crypto/utils.zig
index 38dc236455..14a235e418 100644
--- a/lib/std/crypto/utils.zig
+++ b/lib/std/crypto/utils.zig
@@ -134,12 +134,8 @@ pub fn timingSafeSub(comptime T: type, a: []const T, b: []const T, result: []T,
 
 /// Sets a slice to zeroes.
 /// Prevents the store from being optimized out.
-pub fn secureZero(comptime T: type, s: []T) void {
-    // TODO: implement `@memset` for non-byte-sized element type in the llvm backend
-    //@memset(@as([]volatile T, s), 0);
-    const ptr = @ptrCast([*]volatile u8, s.ptr);
-    const length = s.len * @sizeOf(T);
-    @memset(ptr[0..length], 0);
+pub inline fn secureZero(comptime T: type, s: []T) void {
+    @memset(@as([]volatile T, s), 0);
 }
 
 test "crypto.utils.timingSafeEql" {
@@ -148,7 +144,7 @@ test "crypto.utils.timingSafeEql" {
     random.bytes(a[0..]);
     random.bytes(b[0..]);
     try testing.expect(!timingSafeEql([100]u8, a, b));
-    mem.copy(u8, a[0..], b[0..]);
+    a = b;
     try testing.expect(timingSafeEql([100]u8, a, b));
 }
 
@@ -201,7 +197,7 @@ test "crypto.utils.secureZero" {
     var a = [_]u8{0xfe} ** 8;
     var b = [_]u8{0xfe} ** 8;
 
-    mem.set(u8, a[0..], 0);
+    @memset(a[0..], 0);
     secureZero(u8, b[0..]);
 
     try testing.expectEqualSlices(u8, a[0..], b[0..]);
diff --git a/lib/std/cstr.zig b/lib/std/cstr.zig
index 52524c5084..8a203e5c8e 100644
--- a/lib/std/cstr.zig
+++ b/lib/std/cstr.zig
@@ -34,7 +34,7 @@ fn testCStrFnsImpl() !void {
 /// Caller owns the returned memory.
 pub fn addNullByte(allocator: mem.Allocator, slice: []const u8) ![:0]u8 {
     const result = try allocator.alloc(u8, slice.len + 1);
-    mem.copy(u8, result, slice);
+    @memcpy(result[0..slice.len], slice);
     result[slice.len] = 0;
     return result[0..slice.len :0];
 }
@@ -78,7 +78,7 @@ pub const NullTerminated2DArray = struct {
             for (slice) |inner| {
                 index_buf[i] = buf.ptr + write_index;
                 i += 1;
-                mem.copy(u8, buf[write_index..], inner);
+                @memcpy(buf[write_index..][0..inner.len], inner);
                 write_index += inner.len;
                 buf[write_index] = 0;
                 write_index += 1;
diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index fc8b55a888..ecc1a9f0cf 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -309,8 +309,8 @@ pub fn panicExtra(
     // error being part of the @panic stack trace (but that error should
     // only happen rarely)
     const msg = std.fmt.bufPrint(buf[0..size], format, args) catch |err| switch (err) {
-        std.fmt.BufPrintError.NoSpaceLeft => blk: {
-            std.mem.copy(u8, buf[size..], trunc_msg);
+        error.NoSpaceLeft => blk: {
+            @memcpy(buf[size..], trunc_msg);
             break :blk &buf;
         },
     };
diff --git a/lib/std/dynamic_library.zig b/lib/std/dynamic_library.zig
index 099ba63204..59ad7429cf 100644
--- a/lib/std/dynamic_library.zig
+++ b/lib/std/dynamic_library.zig
@@ -210,7 +210,7 @@ pub const ElfDynLib = struct {
                                 -1,
                                 0,
                             );
-                            mem.copy(u8, sect_mem, file_bytes[0..ph.p_filesz]);
+                            @memcpy(sect_mem[0..ph.p_filesz], file_bytes[0..ph.p_filesz]);
                         }
                     },
                     else => {},
diff --git a/lib/std/enums.zig b/lib/std/enums.zig
index a915d40f49..8e67c358b7 100644
--- a/lib/std/enums.zig
+++ b/lib/std/enums.zig
@@ -275,7 +275,7 @@ pub fn EnumMap(comptime E: type, comptime V: type) type {
                         .bits = Self.BitSet.initFull(),
                         .values = undefined,
                     };
-                    std.mem.set(V, &result.values, value);
+                    @memset(&result.values, value);
                     return result;
                 }
                 /// Initializes a full mapping with supplied values.
@@ -1175,7 +1175,7 @@ pub fn IndexedArray(comptime I: type, comptime V: type, comptime Ext: fn (type)
 
         pub fn initFill(v: Value) Self {
             var self: Self = undefined;
-            std.mem.set(Value, &self.values, v);
+            @memset(&self.values, v);
             return self;
         }
 
diff --git a/lib/std/fifo.zig b/lib/std/fifo.zig
index a6736e41a7..0861e19d14 100644
--- a/lib/std/fifo.zig
+++ b/lib/std/fifo.zig
@@ -86,19 +86,17 @@ pub fn LinearFifo(
 
         pub fn realign(self: *Self) void {
             if (self.buf.len - self.head >= self.count) {
-                // this copy overlaps
-                mem.copy(T, self.buf[0..self.count], self.buf[self.head..][0..self.count]);
+                mem.copyForwards(T, self.buf[0..self.count], self.buf[self.head..][0..self.count]);
                 self.head = 0;
             } else {
                 var tmp: [mem.page_size / 2 / @sizeOf(T)]T = undefined;
 
                 while (self.head != 0) {
-                    const n = math.min(self.head, tmp.len);
+                    const n = @min(self.head, tmp.len);
                     const m = self.buf.len - n;
-                    mem.copy(T, tmp[0..n], self.buf[0..n]);
-                    // this middle copy overlaps; the others here don't
-                    mem.copy(T, self.buf[0..m], self.buf[n..][0..m]);
-                    mem.copy(T, self.buf[m..], tmp[0..n]);
+                    @memcpy(tmp[0..n], self.buf[0..n]);
+                    mem.copyForwards(T, self.buf[0..m], self.buf[n..][0..m]);
+                    @memcpy(self.buf[m..][0..n], tmp[0..n]);
                     self.head -= n;
                 }
             }
@@ -223,8 +221,8 @@ pub fn LinearFifo(
             while (dst_left.len > 0) {
                 const slice = self.readableSlice(0);
                 if (slice.len == 0) break;
-                const n = math.min(slice.len, dst_left.len);
-                mem.copy(T, dst_left, slice[0..n]);
+                const n = @min(slice.len, dst_left.len);
+                @memcpy(dst_left[0..n], slice[0..n]);
                 self.discard(n);
                 dst_left = dst_left[n..];
             }
@@ -289,8 +287,8 @@ pub fn LinearFifo(
             while (src_left.len > 0) {
                 const writable_slice = self.writableSlice(0);
                 assert(writable_slice.len != 0);
-                const n = math.min(writable_slice.len, src_left.len);
-                mem.copy(T, writable_slice, src_left[0..n]);
+                const n = @min(writable_slice.len, src_left.len);
+                @memcpy(writable_slice[0..n], src_left[0..n]);
                 self.update(n);
                 src_left = src_left[n..];
             }
@@ -354,11 +352,11 @@ pub fn LinearFifo(
 
             const slice = self.readableSliceMut(0);
             if (src.len < slice.len) {
-                mem.copy(T, slice, src);
+                @memcpy(slice[0..src.len], src);
             } else {
-                mem.copy(T, slice, src[0..slice.len]);
+                @memcpy(slice, src[0..slice.len]);
                 const slice2 = self.readableSliceMut(slice.len);
-                mem.copy(T, slice2, src[slice.len..]);
+                @memcpy(slice2[0 .. src.len - slice.len], src[slice.len..]);
             }
         }
 
diff --git a/lib/std/fmt/errol.zig b/lib/std/fmt/errol.zig
index 1c67175ede..9ad5d218a9 100644
--- a/lib/std/fmt/errol.zig
+++ b/lib/std/fmt/errol.zig
@@ -84,8 +84,8 @@ pub fn errol3(value: f64, buffer: []u8) FloatDecimal {
     const i = tableLowerBound(bits);
     if (i < enum3.len and enum3[i] == bits) {
         const data = enum3_data[i];
-        const digits = buffer[1 .. data.str.len + 1];
-        mem.copy(u8, digits, data.str);
+        const digits = buffer[1..][0..data.str.len];
+        @memcpy(digits, data.str);
         return FloatDecimal{
             .digits = digits,
             .exp = data.exp,
diff --git a/lib/std/fs.zig b/lib/std/fs.zig
index 290eb151f7..9f64387bd8 100644
--- a/lib/std/fs.zig
+++ b/lib/std/fs.zig
@@ -106,7 +106,7 @@ pub fn atomicSymLink(allocator: Allocator, existing_path: []const u8, new_path:
     var rand_buf: [AtomicFile.RANDOM_BYTES]u8 = undefined;
     const tmp_path = try allocator.alloc(u8, dirname.len + 1 + base64_encoder.calcSize(rand_buf.len));
     defer allocator.free(tmp_path);
-    mem.copy(u8, tmp_path[0..], dirname);
+    @memcpy(tmp_path[0..dirname.len], dirname);
     tmp_path[dirname.len] = path.sep;
     while (true) {
         crypto.random.bytes(rand_buf[0..]);
@@ -1541,9 +1541,9 @@ pub const Dir = struct {
             return error.NameTooLong;
         }
 
-        mem.copy(u8, out_buffer, out_path);
-
-        return out_buffer[0..out_path.len];
+        const result = out_buffer[0..out_path.len];
+        @memcpy(result, out_path);
+        return result;
     }
 
     /// Windows-only. Same as `Dir.realpath` except `pathname` is WTF16 encoded.
@@ -1593,9 +1593,9 @@ pub const Dir = struct {
             return error.NameTooLong;
         }
 
-        mem.copy(u8, out_buffer, out_path);
-
-        return out_buffer[0..out_path.len];
+        const result = out_buffer[0..out_path.len];
+        @memcpy(result, out_path);
+        return result;
     }
 
     /// Same as `Dir.realpath` except caller must free the returned memory.
@@ -2346,8 +2346,9 @@ pub const Dir = struct {
                             if (cleanup_dir_parent) |*d| d.close();
                             cleanup_dir_parent = iterable_dir;
                             iterable_dir = new_dir;
-                            mem.copy(u8, &dir_name_buf, entry.name);
-                            dir_name = dir_name_buf[0..entry.name.len];
+                            const result = dir_name_buf[0..entry.name.len];
+                            @memcpy(result, entry.name);
+                            dir_name = result;
                             continue :scan_dir;
                         } else {
                             if (iterable_dir.dir.deleteFile(entry.name)) {
@@ -2974,8 +2975,9 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
         var real_path_buf: [MAX_PATH_BYTES]u8 = undefined;
         const real_path = try std.os.realpathZ(&symlink_path_buf, &real_path_buf);
         if (real_path.len > out_buffer.len) return error.NameTooLong;
-        std.mem.copy(u8, out_buffer, real_path);
-        return out_buffer[0..real_path.len];
+        const result = out_buffer[0..real_path.len];
+        @memcpy(result, real_path);
+        return result;
     }
     switch (builtin.os.tag) {
         .linux => return os.readlinkZ("/proc/self/exe", out_buffer),
@@ -3014,8 +3016,9 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
                 const real_path = try os.realpathZ(os.argv[0], &real_path_buf);
                 if (real_path.len > out_buffer.len)
                     return error.NameTooLong;
-                mem.copy(u8, out_buffer, real_path);
-                return out_buffer[0..real_path.len];
+                const result = out_buffer[0..real_path.len];
+                @memcpy(result, real_path);
+                return result;
             } else if (argv0.len != 0) {
                 // argv[0] is not empty (and not a path): search it inside PATH
                 const PATH = std.os.getenvZ("PATH") orelse return error.FileNotFound;
@@ -3032,8 +3035,9 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
                         // found a file, and hope it is the right file
                         if (real_path.len > out_buffer.len)
                             return error.NameTooLong;
-                        mem.copy(u8, out_buffer, real_path);
-                        return out_buffer[0..real_path.len];
+                        const result = out_buffer[0..real_path.len];
+                        @memcpy(result, real_path);
+                        return result;
                     } else |_| continue;
                 }
             }
diff --git a/lib/std/fs/path.zig b/lib/std/fs/path.zig
index beb386f92c..4f3e05cd59 100644
--- a/lib/std/fs/path.zig
+++ b/lib/std/fs/path.zig
@@ -79,7 +79,7 @@ fn joinSepMaybeZ(allocator: Allocator, separator: u8, comptime sepPredicate: fn
     const buf = try allocator.alloc(u8, total_len);
     errdefer allocator.free(buf);
 
-    mem.copy(u8, buf, paths[first_path_index]);
+    @memcpy(buf[0..paths[first_path_index].len], paths[first_path_index]);
     var buf_index: usize = paths[first_path_index].len;
     var prev_path = paths[first_path_index];
     assert(prev_path.len > 0);
@@ -94,7 +94,7 @@ fn joinSepMaybeZ(allocator: Allocator, separator: u8, comptime sepPredicate: fn
             buf_index += 1;
         }
         const adjusted_path = if (prev_sep and this_sep) this_path[1..] else this_path;
-        mem.copy(u8, buf[buf_index..], adjusted_path);
+        @memcpy(buf[buf_index..][0..adjusted_path.len], adjusted_path);
         buf_index += adjusted_path.len;
         prev_path = this_path;
     }
@@ -631,7 +631,7 @@ pub fn resolveWindows(allocator: Allocator, paths: []const []const u8) ![]u8 {
             real_result[i..][0..3].* = "..\\".*;
             i += 3;
         }
-        mem.copy(u8, real_result[i..], result.items);
+        @memcpy(real_result[i..][0..result.items.len], result.items);
         return real_result;
     }
 }
@@ -710,7 +710,7 @@ pub fn resolvePosix(allocator: Allocator, paths: []const []const u8) Allocator.E
             real_result[i..][0..3].* = "../".*;
             i += 3;
         }
-        mem.copy(u8, real_result[i..], result.items);
+        @memcpy(real_result[i..][0..result.items.len], result.items);
         return real_result;
     }
 }
@@ -1106,7 +1106,7 @@ pub fn relativeWindows(allocator: Allocator, from: []const u8, to: []const u8) !
         while (rest_it.next()) |to_component| {
             result[result_index] = '\\';
             result_index += 1;
-            mem.copy(u8, result[result_index..], to_component);
+            @memcpy(result[result_index..][0..to_component.len], to_component);
             result_index += to_component.len;
         }
 
@@ -1151,7 +1151,7 @@ pub fn relativePosix(allocator: Allocator, from: []const u8, to: []const u8) ![]
             return allocator.realloc(result, result_index - 1);
         }
 
-        mem.copy(u8, result[result_index..], to_rest);
+        @memcpy(result[result_index..][0..to_rest.len], to_rest);
         return result;
     }
 
diff --git a/lib/std/hash/cityhash.zig b/lib/std/hash/cityhash.zig
index 23b3ce02da..d0884b135f 100644
--- a/lib/std/hash/cityhash.zig
+++ b/lib/std/hash/cityhash.zig
@@ -348,8 +348,8 @@ fn SMHasherTest(comptime hash_fn: anytype) u32 {
     var key: [256]u8 = undefined;
     var hashes_bytes: [256 * @sizeOf(HashResult)]u8 = undefined;
 
-    std.mem.set(u8, &key, 0);
-    std.mem.set(u8, &hashes_bytes, 0);
+    @memset(&key, 0);
+    @memset(&hashes_bytes, 0);
 
     var i: u32 = 0;
     while (i < 256) : (i += 1) {
diff --git a/lib/std/hash/wyhash.zig b/lib/std/hash/wyhash.zig
index 2f30c26b75..772395eab9 100644
--- a/lib/std/hash/wyhash.zig
+++ b/lib/std/hash/wyhash.zig
@@ -147,7 +147,7 @@ pub const Wyhash = struct {
 
         if (self.buf_len != 0 and self.buf_len + b.len >= 32) {
             off += 32 - self.buf_len;
-            mem.copy(u8, self.buf[self.buf_len..], b[0..off]);
+            @memcpy(self.buf[self.buf_len..][0..off], b[0..off]);
             self.state.update(self.buf[0..]);
             self.buf_len = 0;
         }
@@ -156,7 +156,8 @@ pub const Wyhash = struct {
         const aligned_len = remain_len - (remain_len % 32);
         self.state.update(b[off .. off + aligned_len]);
 
-        mem.copy(u8, self.buf[self.buf_len..], b[off + aligned_len ..]);
+        const src = b[off + aligned_len ..];
+        @memcpy(self.buf[self.buf_len..][0..src.len], src);
         self.buf_len += @intCast(u8, b[off + aligned_len ..].len);
     }
 
diff --git a/lib/std/hash/xxhash.zig b/lib/std/hash/xxhash.zig
index bf4877e029..88db1dc1bd 100644
--- a/lib/std/hash/xxhash.zig
+++ b/lib/std/hash/xxhash.zig
@@ -36,7 +36,7 @@ pub const XxHash64 = struct {
 
     pub fn update(self: *XxHash64, input: []const u8) void {
         if (input.len < 32 - self.buf_len) {
-            mem.copy(u8, self.buf[self.buf_len..], input);
+            @memcpy(self.buf[self.buf_len..][0..input.len], input);
             self.buf_len += input.len;
             return;
         }
@@ -45,7 +45,7 @@ pub const XxHash64 = struct {
 
         if (self.buf_len > 0) {
             i = 32 - self.buf_len;
-            mem.copy(u8, self.buf[self.buf_len..], input[0..i]);
+            @memcpy(self.buf[self.buf_len..][0..i], input[0..i]);
             self.processStripe(&self.buf);
             self.buf_len = 0;
         }
@@ -55,7 +55,7 @@ pub const XxHash64 = struct {
         }
 
         const remaining_bytes = input[i..];
-        mem.copy(u8, &self.buf, remaining_bytes);
+        @memcpy(self.buf[0..remaining_bytes.len], remaining_bytes);
         self.buf_len = remaining_bytes.len;
     }
 
@@ -165,7 +165,7 @@ pub const XxHash32 = struct {
 
     pub fn update(self: *XxHash32, input: []const u8) void {
         if (input.len < 16 - self.buf_len) {
-            mem.copy(u8, self.buf[self.buf_len..], input);
+            @memcpy(self.buf[self.buf_len..][0..input.len], input);
             self.buf_len += input.len;
             return;
         }
@@ -174,7 +174,7 @@ pub const XxHash32 = struct {
 
         if (self.buf_len > 0) {
             i = 16 - self.buf_len;
-            mem.copy(u8, self.buf[self.buf_len..], input[0..i]);
+            @memcpy(self.buf[self.buf_len..][0..i], input[0..i]);
             self.processStripe(&self.buf);
             self.buf_len = 0;
         }
@@ -184,7 +184,7 @@ pub const XxHash32 = struct {
         }
 
         const remaining_bytes = input[i..];
-        mem.copy(u8, &self.buf, remaining_bytes);
+        @memcpy(self.buf[0..remaining_bytes.len], remaining_bytes);
         self.buf_len = remaining_bytes.len;
     }
 
diff --git a/lib/std/heap/WasmAllocator.zig b/lib/std/heap/WasmAllocator.zig
index 3b980ac9d3..efec116db4 100644
--- a/lib/std/heap/WasmAllocator.zig
+++ b/lib/std/heap/WasmAllocator.zig
@@ -230,7 +230,7 @@ test "shrink" {
     var slice = try test_ally.alloc(u8, 20);
     defer test_ally.free(slice);
 
-    mem.set(u8, slice, 0x11);
+    @memset(slice, 0x11);
 
     try std.testing.expect(test_ally.resize(slice, 17));
     slice = slice[0..17];
diff --git a/lib/std/heap/WasmPageAllocator.zig b/lib/std/heap/WasmPageAllocator.zig
index 4084eaa88e..1370af022c 100644
--- a/lib/std/heap/WasmPageAllocator.zig
+++ b/lib/std/heap/WasmPageAllocator.zig
@@ -153,7 +153,7 @@ fn freePages(start: usize, end: usize) void {
 
             extended.data = @intToPtr([*]u128, new_end * mem.page_size)[0 .. mem.page_size / @sizeOf(u128)];
             // Since this is the first page being freed and we consume it, assume *nothing* is free.
-            mem.set(u128, extended.data, PageStatus.none_free);
+            @memset(extended.data, PageStatus.none_free);
         }
         const clamped_start = @max(extendedOffset(), start);
         extended.recycle(clamped_start - extendedOffset(), new_end - clamped_start);
diff --git a/lib/std/heap/general_purpose_allocator.zig b/lib/std/heap/general_purpose_allocator.zig
index e7ebe75812..de7bc7c423 100644
--- a/lib/std/heap/general_purpose_allocator.zig
+++ b/lib/std/heap/general_purpose_allocator.zig
@@ -448,7 +448,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
 
         fn collectStackTrace(first_trace_addr: usize, addresses: *[stack_n]usize) void {
             if (stack_n == 0) return;
-            mem.set(usize, addresses, 0);
+            @memset(addresses, 0);
             var stack_trace = StackTrace{
                 .instruction_addresses = addresses,
                 .index = 0,
@@ -1113,7 +1113,7 @@ test "shrink" {
     var slice = try allocator.alloc(u8, 20);
     defer allocator.free(slice);
 
-    mem.set(u8, slice, 0x11);
+    @memset(slice, 0x11);
 
     try std.testing.expect(allocator.resize(slice, 17));
     slice = slice[0..17];
diff --git a/lib/std/http/Client.zig b/lib/std/http/Client.zig
index e1f28e7921..42ef766bd3 100644
--- a/lib/std/http/Client.zig
+++ b/lib/std/http/Client.zig
@@ -284,7 +284,7 @@ pub const BufferedConnection = struct {
             if (available > 0) {
                 const can_read = @truncate(u16, @min(available, left));
 
-                std.mem.copy(u8, buffer[out_index..], bconn.buf[bconn.start..][0..can_read]);
+                @memcpy(buffer[out_index..][0..can_read], bconn.buf[bconn.start..][0..can_read]);
                 out_index += can_read;
                 bconn.start += can_read;
 
diff --git a/lib/std/http/Headers.zig b/lib/std/http/Headers.zig
index 0322c32481..376fd60b61 100644
--- a/lib/std/http/Headers.zig
+++ b/lib/std/http/Headers.zig
@@ -38,7 +38,8 @@ pub const Field = struct {
 
     pub fn modify(entry: *Field, allocator: Allocator, new_value: []const u8) !void {
         if (entry.value.len <= new_value.len) {
-            std.mem.copy(u8, @constCast(entry.value), new_value);
+            // TODO: eliminate this use of `@constCast`.
+            @memcpy(@constCast(entry.value)[0..new_value.len], new_value);
         } else {
             allocator.free(entry.value);
 
diff --git a/lib/std/http/Server.zig b/lib/std/http/Server.zig
index 66adb1bb96..c7f2a86c27 100644
--- a/lib/std/http/Server.zig
+++ b/lib/std/http/Server.zig
@@ -128,7 +128,7 @@ pub const BufferedConnection = struct {
             if (available > 0) {
                 const can_read = @truncate(u16, @min(available, left));
 
-                std.mem.copy(u8, buffer[out_index..], bconn.buf[bconn.start..][0..can_read]);
+                @memcpy(buffer[out_index..][0..can_read], bconn.buf[bconn.start..][0..can_read]);
                 out_index += can_read;
                 bconn.start += can_read;
 
diff --git a/lib/std/http/protocol.zig b/lib/std/http/protocol.zig
index 962376ce82..c6bdd76272 100644
--- a/lib/std/http/protocol.zig
+++ b/lib/std/http/protocol.zig
@@ -654,7 +654,7 @@ const MockBufferedConnection = struct {
             if (available > 0) {
                 const can_read = @truncate(u16, @min(available, left));
 
-                std.mem.copy(u8, buffer[out_index..], bconn.buf[bconn.start..][0..can_read]);
+                @memcpy(buffer[out_index..][0..can_read], bconn.buf[bconn.start..][0..can_read]);
                 out_index += can_read;
                 bconn.start += can_read;
 
diff --git a/lib/std/io/buffered_reader.zig b/lib/std/io/buffered_reader.zig
index 2f6677c6a5..efc1d78cc4 100644
--- a/lib/std/io/buffered_reader.zig
+++ b/lib/std/io/buffered_reader.zig
@@ -20,8 +20,8 @@ pub fn BufferedReader(comptime buffer_size: usize, comptime ReaderType: type) ty
             var dest_index: usize = 0;
 
             while (dest_index < dest.len) {
-                const written = std.math.min(dest.len - dest_index, self.end - self.start);
-                std.mem.copy(u8, dest[dest_index..], self.buf[self.start .. self.start + written]);
+                const written = @min(dest.len - dest_index, self.end - self.start);
+                @memcpy(dest[dest_index..][0..written], self.buf[self.start..][0..written]);
                 if (written == 0) {
                     // buf empty, fill it
                     const n = try self.unbuffered_reader.read(self.buf[0..]);
@@ -115,11 +115,8 @@ test "io.BufferedReader Block" {
         }
 
         fn read(self: *Self, dest: []u8) Error!usize {
-            if (self.curr_read >= self.reads_allowed) {
-                return 0;
-            }
-            std.debug.assert(dest.len >= self.block.len);
-            std.mem.copy(u8, dest, self.block);
+            if (self.curr_read >= self.reads_allowed) return 0;
+            @memcpy(dest[0..self.block.len], self.block);
 
             self.curr_read += 1;
             return self.block.len;
diff --git a/lib/std/io/buffered_writer.zig b/lib/std/io/buffered_writer.zig
index 497a1810a7..906d6cce49 100644
--- a/lib/std/io/buffered_writer.zig
+++ b/lib/std/io/buffered_writer.zig
@@ -30,8 +30,9 @@ pub fn BufferedWriter(comptime buffer_size: usize, comptime WriterType: type) ty
                     return self.unbuffered_writer.write(bytes);
             }
 
-            mem.copy(u8, self.buf[self.end..], bytes);
-            self.end += bytes.len;
+            const new_end = self.end + bytes.len;
+            @memcpy(self.buf[self.end..new_end], bytes);
+            self.end = new_end;
             return bytes.len;
         }
     };
diff --git a/lib/std/io/fixed_buffer_stream.zig b/lib/std/io/fixed_buffer_stream.zig
index 2fcb260c72..c170dd1f74 100644
--- a/lib/std/io/fixed_buffer_stream.zig
+++ b/lib/std/io/fixed_buffer_stream.zig
@@ -45,10 +45,10 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
         }
 
         pub fn read(self: *Self, dest: []u8) ReadError!usize {
-            const size = std.math.min(dest.len, self.buffer.len - self.pos);
+            const size = @min(dest.len, self.buffer.len - self.pos);
             const end = self.pos + size;
 
-            mem.copy(u8, dest[0..size], self.buffer[self.pos..end]);
+            @memcpy(dest[0..size], self.buffer[self.pos..end]);
             self.pos = end;
 
             return size;
@@ -67,7 +67,7 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
             else
                 self.buffer.len - self.pos;
 
-            mem.copy(u8, self.buffer[self.pos .. self.pos + n], bytes[0..n]);
+            @memcpy(self.buffer[self.pos..][0..n], bytes[0..n]);
             self.pos += n;
 
             if (n == 0) return error.NoSpaceLeft;
diff --git a/lib/std/io/writer.zig b/lib/std/io/writer.zig
index 3160c37ff2..f4b2643e77 100644
--- a/lib/std/io/writer.zig
+++ b/lib/std/io/writer.zig
@@ -35,7 +35,7 @@ pub fn Writer(
 
         pub fn writeByteNTimes(self: Self, byte: u8, n: usize) Error!void {
             var bytes: [256]u8 = undefined;
-            mem.set(u8, bytes[0..], byte);
+            @memset(bytes[0..], byte);
 
             var remaining: usize = n;
             while (remaining > 0) {
diff --git a/lib/std/json.zig b/lib/std/json.zig
index ca7fb5ad20..432f4e6911 100644
--- a/lib/std/json.zig
+++ b/lib/std/json.zig
@@ -1667,7 +1667,7 @@ fn parseInternal(
                     const source_slice = stringToken.slice(tokens.slice, tokens.i - 1);
                     if (r.len != stringToken.decodedLength()) return error.LengthMismatch;
                     switch (stringToken.escapes) {
-                        .None => mem.copy(u8, &r, source_slice),
+                        .None => @memcpy(r[0..source_slice.len], source_slice),
                         .Some => try unescapeValidString(&r, source_slice),
                     }
                     return r;
@@ -1733,7 +1733,7 @@ fn parseInternal(
                                 try allocator.alloc(u8, len);
                             errdefer allocator.free(output);
                             switch (stringToken.escapes) {
-                                .None => mem.copy(u8, output, source_slice),
+                                .None => @memcpy(output[0..source_slice.len], source_slice),
                                 .Some => try unescapeValidString(output, source_slice),
                             }
 
diff --git a/lib/std/json/test.zig b/lib/std/json/test.zig
index 452341535b..7b5e7e814d 100644
--- a/lib/std/json/test.zig
+++ b/lib/std/json/test.zig
@@ -2811,7 +2811,7 @@ test "json.serialize issue #5959" {
     // StreamingParser has multiple internal fields set to undefined. This causes issues when using
     // expectEqual so these are zeroed. We are testing for equality here only because this is a
     // known small test reproduction which hits the relevant LLVM issue.
-    std.mem.set(u8, @ptrCast([*]u8, &parser)[0..@sizeOf(StreamingParser)], 0);
+    @memset(@ptrCast([*]u8, &parser)[0..@sizeOf(StreamingParser)], 0);
     try std.testing.expectEqual(parser, parser);
 }
 
diff --git a/lib/std/math/big/int.zig b/lib/std/math/big/int.zig
index f97a763d95..2406d669ec 100644
--- a/lib/std/math/big/int.zig
+++ b/lib/std/math/big/int.zig
@@ -176,7 +176,7 @@ pub const Mutable = struct {
     /// Asserts the value fits in the limbs buffer.
     pub fn copy(self: *Mutable, other: Const) void {
         if (self.limbs.ptr != other.limbs.ptr) {
-            mem.copy(Limb, self.limbs[0..], other.limbs[0..other.limbs.len]);
+            @memcpy(self.limbs[0..other.limbs.len], other.limbs[0..other.limbs.len]);
         }
         self.positive = other.positive;
         self.len = other.limbs.len;
@@ -199,7 +199,7 @@ pub const Mutable = struct {
     /// can be modified separately from the original.
     /// Asserts that limbs is big enough to store the value.
     pub fn clone(other: Mutable, limbs: []Limb) Mutable {
-        mem.copy(Limb, limbs, other.limbs[0..other.len]);
+        @memcpy(limbs[0..other.len], other.limbs[0..other.len]);
         return .{
             .limbs = limbs,
             .len = other.len,
@@ -344,7 +344,7 @@ pub const Mutable = struct {
                 .min => {
                     // Negative bound, signed = -0x80.
                     r.len = req_limbs;
-                    mem.set(Limb, r.limbs[0 .. r.len - 1], 0);
+                    @memset(r.limbs[0 .. r.len - 1], 0);
                     r.limbs[r.len - 1] = signmask;
                     r.positive = false;
                 },
@@ -363,7 +363,7 @@ pub const Mutable = struct {
                         const new_mask = (new_signmask << 1) -% 1; // 0b0..001..1 where the rightmost 0 is the sign bit.
 
                         r.len = new_req_limbs;
-                        std.mem.set(Limb, r.limbs[0 .. r.len - 1], maxInt(Limb));
+                        @memset(r.limbs[0 .. r.len - 1], maxInt(Limb));
                         r.limbs[r.len - 1] = new_mask;
                     }
                 },
@@ -376,7 +376,7 @@ pub const Mutable = struct {
                 .max => {
                     // Max bound, unsigned = 0xFF
                     r.len = req_limbs;
-                    std.mem.set(Limb, r.limbs[0 .. r.len - 1], maxInt(Limb));
+                    @memset(r.limbs[0 .. r.len - 1], maxInt(Limb));
                     r.limbs[r.len - 1] = mask;
                 },
             },
@@ -489,7 +489,7 @@ pub const Mutable = struct {
             if (msl < req_limbs) {
                 r.limbs[msl] = 1;
                 r.len = req_limbs;
-                mem.set(Limb, r.limbs[msl + 1 .. req_limbs], 0);
+                @memset(r.limbs[msl + 1 .. req_limbs], 0);
             } else {
                 carry_truncated = true;
             }
@@ -637,14 +637,14 @@ pub const Mutable = struct {
 
         const a_copy = if (rma.limbs.ptr == a.limbs.ptr) blk: {
             const start = buf_index;
-            mem.copy(Limb, limbs_buffer[buf_index..], a.limbs);
+            @memcpy(limbs_buffer[buf_index..][0..a.limbs.len], a.limbs);
             buf_index += a.limbs.len;
             break :blk a.toMutable(limbs_buffer[start..buf_index]).toConst();
         } else a;
 
         const b_copy = if (rma.limbs.ptr == b.limbs.ptr) blk: {
             const start = buf_index;
-            mem.copy(Limb, limbs_buffer[buf_index..], b.limbs);
+            @memcpy(limbs_buffer[buf_index..][0..b.limbs.len], b.limbs);
             buf_index += b.limbs.len;
             break :blk b.toMutable(limbs_buffer[start..buf_index]).toConst();
         } else b;
@@ -676,7 +676,7 @@ pub const Mutable = struct {
             }
         }
 
-        mem.set(Limb, rma.limbs[0 .. a.limbs.len + b.limbs.len], 0);
+        @memset(rma.limbs[0 .. a.limbs.len + b.limbs.len], 0);
 
         llmulacc(.add, allocator, rma.limbs, a.limbs, b.limbs);
 
@@ -708,7 +708,7 @@ pub const Mutable = struct {
         const a_copy = if (rma.limbs.ptr == a.limbs.ptr) blk: {
             const start = buf_index;
             const a_len = math.min(req_limbs, a.limbs.len);
-            mem.copy(Limb, limbs_buffer[buf_index..], a.limbs[0..a_len]);
+            @memcpy(limbs_buffer[buf_index..][0..a_len], a.limbs[0..a_len]);
             buf_index += a_len;
             break :blk a.toMutable(limbs_buffer[start..buf_index]).toConst();
         } else a;
@@ -716,7 +716,7 @@ pub const Mutable = struct {
         const b_copy = if (rma.limbs.ptr == b.limbs.ptr) blk: {
             const start = buf_index;
             const b_len = math.min(req_limbs, b.limbs.len);
-            mem.copy(Limb, limbs_buffer[buf_index..], b.limbs[0..b_len]);
+            @memcpy(limbs_buffer[buf_index..][0..b_len], b.limbs[0..b_len]);
             buf_index += b_len;
             break :blk a.toMutable(limbs_buffer[start..buf_index]).toConst();
         } else b;
@@ -751,7 +751,7 @@ pub const Mutable = struct {
         const a_limbs = a.limbs[0..math.min(req_limbs, a.limbs.len)];
         const b_limbs = b.limbs[0..math.min(req_limbs, b.limbs.len)];
 
-        mem.set(Limb, rma.limbs[0..req_limbs], 0);
+        @memset(rma.limbs[0..req_limbs], 0);
 
         llmulacc(.add, allocator, rma.limbs, a_limbs, b_limbs);
         rma.normalize(math.min(req_limbs, a.limbs.len + b.limbs.len));
@@ -919,7 +919,7 @@ pub const Mutable = struct {
         _ = opt_allocator;
         assert(rma.limbs.ptr != a.limbs.ptr); // illegal aliasing
 
-        mem.set(Limb, rma.limbs, 0);
+        @memset(rma.limbs, 0);
 
         llsquareBasecase(rma.limbs, a.limbs);
 
@@ -1522,7 +1522,7 @@ pub const Mutable = struct {
         if (xy_trailing != 0) {
             // Manually shift here since we know its limb aligned.
             mem.copyBackwards(Limb, r.limbs[xy_trailing..], r.limbs[0..r.len]);
-            mem.set(Limb, r.limbs[0..xy_trailing], 0);
+            @memset(r.limbs[0..xy_trailing], 0);
             r.len += xy_trailing;
         }
     }
@@ -1556,7 +1556,7 @@ pub const Mutable = struct {
         // for 0 <= j <= n - t, set q[j] to 0
         q.len = shift + 1;
         q.positive = true;
-        mem.set(Limb, q.limbs[0..q.len], 0);
+        @memset(q.limbs[0..q.len], 0);
 
         // 2.
         // while x >= y * b^(n - t):
@@ -1691,7 +1691,7 @@ pub const Mutable = struct {
 
         r.addScalar(a.abs(), -1);
         if (req_limbs > r.len) {
-            mem.set(Limb, r.limbs[r.len..req_limbs], 0);
+            @memset(r.limbs[r.len..req_limbs], 0);
         }
 
         assert(r.limbs.len >= req_limbs);
@@ -1730,7 +1730,7 @@ pub const Mutable = struct {
 
             // Zero-extend the result
             if (req_limbs > r.len) {
-                mem.set(Limb, r.limbs[r.len..req_limbs], 0);
+                @memset(r.limbs[r.len..req_limbs], 0);
             }
 
             // Truncate to required number of limbs.
@@ -1921,8 +1921,8 @@ pub const Const = struct {
 
     /// The result is an independent resource which is managed by the caller.
     pub fn toManaged(self: Const, allocator: Allocator) Allocator.Error!Managed {
-        const limbs = try allocator.alloc(Limb, math.max(Managed.default_capacity, self.limbs.len));
-        mem.copy(Limb, limbs, self.limbs);
+        const limbs = try allocator.alloc(Limb, @max(Managed.default_capacity, self.limbs.len));
+        @memcpy(limbs[0..self.limbs.len], self.limbs);
         return Managed{
             .allocator = allocator,
             .limbs = limbs,
@@ -1935,7 +1935,7 @@ pub const Const = struct {
 
     /// Asserts `limbs` is big enough to store the value.
     pub fn toMutable(self: Const, limbs: []Limb) Mutable {
-        mem.copy(Limb, limbs, self.limbs[0..self.limbs.len]);
+        @memcpy(limbs[0..self.limbs.len], self.limbs[0..self.limbs.len]);
         return .{
             .limbs = limbs,
             .positive = self.positive,
@@ -2253,7 +2253,7 @@ pub const Const = struct {
                 .positive = true, // Make absolute by ignoring self.positive.
                 .len = self.limbs.len,
             };
-            mem.copy(Limb, q.limbs, self.limbs);
+            @memcpy(q.limbs[0..self.limbs.len], self.limbs);
 
             var r: Mutable = .{
                 .limbs = limbs_buffer[q.limbs.len..][0..self.limbs.len],
@@ -2587,8 +2587,8 @@ pub const Managed = struct {
             .allocator = allocator,
             .metadata = other.metadata,
             .limbs = block: {
-                var limbs = try allocator.alloc(Limb, other.len());
-                mem.copy(Limb, limbs[0..], other.limbs[0..other.len()]);
+                const limbs = try allocator.alloc(Limb, other.len());
+                @memcpy(limbs, other.limbs[0..other.len()]);
                 break :block limbs;
             },
         };
@@ -2600,7 +2600,7 @@ pub const Managed = struct {
         if (self.limbs.ptr == other.limbs.ptr) return;
 
         try self.ensureCapacity(other.limbs.len);
-        mem.copy(Limb, self.limbs[0..], other.limbs[0..other.limbs.len]);
+        @memcpy(self.limbs[0..other.limbs.len], other.limbs[0..other.limbs.len]);
         self.setMetadata(other.positive, other.limbs.len);
     }
 
@@ -3302,7 +3302,7 @@ fn llmulaccKaratsuba(
     // Note, we don't need to compute all of p2, just enough limbs to satisfy r.
     const p2_limbs = math.min(limbs_after_split, a1.len + b1.len);
 
-    mem.set(Limb, tmp[0..p2_limbs], 0);
+    @memset(tmp[0..p2_limbs], 0);
     llmulacc(.add, allocator, tmp[0..p2_limbs], a1[0..math.min(a1.len, p2_limbs)], b1[0..math.min(b1.len, p2_limbs)]);
     const p2 = tmp[0..llnormalize(tmp[0..p2_limbs])];
 
@@ -3317,7 +3317,7 @@ fn llmulaccKaratsuba(
     // Compute p0.
     // Since a0.len, b0.len <= split and r.len >= split * 2, the full width of p0 needs to be computed.
     const p0_limbs = a0.len + b0.len;
-    mem.set(Limb, tmp[0..p0_limbs], 0);
+    @memset(tmp[0..p0_limbs], 0);
     llmulacc(.add, allocator, tmp[0..p0_limbs], a0, b0);
     const p0 = tmp[0..llnormalize(tmp[0..p0_limbs])];
 
@@ -3341,7 +3341,7 @@ fn llmulaccKaratsuba(
         return;
     }
 
-    mem.set(Limb, tmp, 0);
+    @memset(tmp, 0);
 
     // p1 is nonzero, so compute the intermediary terms j0 = a0 - a1 and j1 = b1 - b0.
     // Note that in this case, we again need some storage for intermediary results
@@ -3666,7 +3666,7 @@ fn llshl(r: []Limb, a: []const Limb, shift: usize) void {
     }
 
     r[limb_shift - 1] = carry;
-    mem.set(Limb, r[0 .. limb_shift - 1], 0);
+    @memset(r[0 .. limb_shift - 1], 0);
 }
 
 fn llshr(r: []Limb, a: []const Limb, shift: usize) void {
@@ -4061,8 +4061,8 @@ fn llpow(r: []Limb, a: []const Limb, b: u32, tmp_limbs: []Limb) void {
         tmp2 = tmp_limbs;
     }
 
-    mem.copy(Limb, tmp1, a);
-    mem.set(Limb, tmp1[a.len..], 0);
+    @memcpy(tmp1[0..a.len], a);
+    @memset(tmp1[a.len..], 0);
 
     // Scan the exponent as a binary number, from left to right, dropping the
     // most significant bit set.
@@ -4074,14 +4074,14 @@ fn llpow(r: []Limb, a: []const Limb, b: u32, tmp_limbs: []Limb) void {
     var i: usize = 0;
     while (i < exp_bits) : (i += 1) {
         // Square
-        mem.set(Limb, tmp2, 0);
+        @memset(tmp2, 0);
         llsquareBasecase(tmp2, tmp1[0..llnormalize(tmp1)]);
         mem.swap([]Limb, &tmp1, &tmp2);
         // Multiply by a
         const ov = @shlWithOverflow(exp, 1);
         exp = ov[0];
         if (ov[1] != 0) {
-            mem.set(Limb, tmp2, 0);
+            @memset(tmp2, 0);
             llmulacc(.add, null, tmp2, tmp1[0..llnormalize(tmp1)], a);
             mem.swap([]Limb, &tmp1, &tmp2);
         }
diff --git a/lib/std/mem.zig b/lib/std/mem.zig
index 4b796c851a..557e39cdfc 100644
--- a/lib/std/mem.zig
+++ b/lib/std/mem.zig
@@ -192,12 +192,15 @@ test "Allocator.resize" {
     }
 }
 
+/// Deprecated: use `@memcpy` if the arguments do not overlap, or
+/// `copyForwards` if they do.
+pub const copy = copyForwards;
+
 /// Copy all of source into dest at position 0.
 /// dest.len must be >= source.len.
 /// If the slices overlap, dest.ptr must be <= src.ptr.
-pub fn copy(comptime T: type, dest: []T, source: []const T) void {
-    for (dest[0..source.len], source) |*d, s|
-        d.* = s;
+pub fn copyForwards(comptime T: type, dest: []T, source: []const T) void {
+    for (dest[0..source.len], source) |*d, s| d.* = s;
 }
 
 /// Copy all of source into dest at position 0.
@@ -216,11 +219,7 @@ pub fn copyBackwards(comptime T: type, dest: []T, source: []const T) void {
     }
 }
 
-/// Sets all elements of `dest` to `value`.
-pub fn set(comptime T: type, dest: []T, value: T) void {
-    for (dest) |*d|
-        d.* = value;
-}
+pub const set = @compileError("deprecated; use @memset instead");
 
 /// Generally, Zig users are encouraged to explicitly initialize all fields of a struct explicitly rather than using this function.
 /// However, it is recognized that there are sometimes use cases for initializing all fields to a "zero" value. For example, when
@@ -249,7 +248,7 @@ pub fn zeroes(comptime T: type) T {
             if (@sizeOf(T) == 0) return undefined;
             if (struct_info.layout == .Extern) {
                 var item: T = undefined;
-                set(u8, asBytes(&item), 0);
+                @memset(asBytes(&item), 0);
                 return item;
             } else {
                 var structure: T = undefined;
@@ -1667,9 +1666,9 @@ pub fn writeIntSliceLittle(comptime T: type, buffer: []u8, value: T) void {
     assert(buffer.len >= @divExact(@typeInfo(T).Int.bits, 8));
 
     if (@typeInfo(T).Int.bits == 0) {
-        return set(u8, buffer, 0);
+        return @memset(buffer, 0);
     } else if (@typeInfo(T).Int.bits == 8) {
-        set(u8, buffer, 0);
+        @memset(buffer, 0);
         buffer[0] = @bitCast(u8, value);
         return;
     }
@@ -1691,9 +1690,9 @@ pub fn writeIntSliceBig(comptime T: type, buffer: []u8, value: T) void {
     assert(buffer.len >= @divExact(@typeInfo(T).Int.bits, 8));
 
     if (@typeInfo(T).Int.bits == 0) {
-        return set(u8, buffer, 0);
+        return @memset(buffer, 0);
     } else if (@typeInfo(T).Int.bits == 8) {
-        set(u8, buffer, 0);
+        @memset(buffer, 0);
         buffer[buffer.len - 1] = @bitCast(u8, value);
         return;
     }
@@ -2706,7 +2705,7 @@ fn testReadIntImpl() !void {
     }
 }
 
-test "writeIntSlice" {
+test writeIntSlice {
     try testWriteIntImpl();
     comptime try testWriteIntImpl();
 }
@@ -3124,7 +3123,7 @@ pub fn replace(comptime T: type, input: []const T, needle: []const T, replacemen
     var replacements: usize = 0;
     while (slide < input.len) {
         if (mem.startsWith(T, input[slide..], needle)) {
-            mem.copy(T, output[i .. i + replacement.len], replacement);
+            @memcpy(output[i..][0..replacement.len], replacement);
             i += replacement.len;
             slide += needle.len;
             replacements += 1;
diff --git a/lib/std/mem/Allocator.zig b/lib/std/mem/Allocator.zig
index b402fab3fa..5110534ed4 100644
--- a/lib/std/mem/Allocator.zig
+++ b/lib/std/mem/Allocator.zig
@@ -307,14 +307,14 @@ pub fn free(self: Allocator, memory: anytype) void {
 /// Copies `m` to newly allocated memory. Caller owns the memory.
 pub fn dupe(allocator: Allocator, comptime T: type, m: []const T) ![]T {
     const new_buf = try allocator.alloc(T, m.len);
-    mem.copy(T, new_buf, m);
+    @memcpy(new_buf, m);
     return new_buf;
 }
 
 /// Copies `m` to newly allocated memory, with a null-terminated element. Caller owns the memory.
 pub fn dupeZ(allocator: Allocator, comptime T: type, m: []const T) ![:0]T {
     const new_buf = try allocator.alloc(T, m.len + 1);
-    mem.copy(T, new_buf, m);
+    @memcpy(new_buf[0..m.len], m);
     new_buf[m.len] = 0;
     return new_buf[0..m.len :0];
 }
diff --git a/lib/std/multi_array_list.zig b/lib/std/multi_array_list.zig
index 063e2e5620..322471bedf 100644
--- a/lib/std/multi_array_list.zig
+++ b/lib/std/multi_array_list.zig
@@ -380,7 +380,7 @@ pub fn MultiArrayList(comptime T: type) type {
             inline for (fields, 0..) |field_info, i| {
                 if (@sizeOf(field_info.type) != 0) {
                     const field = @intToEnum(Field, i);
-                    mem.copy(field_info.type, other_slice.items(field), self_slice.items(field));
+                    @memcpy(other_slice.items(field), self_slice.items(field));
                 }
             }
             gpa.free(self.allocatedBytes());
@@ -441,7 +441,7 @@ pub fn MultiArrayList(comptime T: type) type {
             inline for (fields, 0..) |field_info, i| {
                 if (@sizeOf(field_info.type) != 0) {
                     const field = @intToEnum(Field, i);
-                    mem.copy(field_info.type, other_slice.items(field), self_slice.items(field));
+                    @memcpy(other_slice.items(field), self_slice.items(field));
                 }
             }
             gpa.free(self.allocatedBytes());
@@ -460,7 +460,7 @@ pub fn MultiArrayList(comptime T: type) type {
             inline for (fields, 0..) |field_info, i| {
                 if (@sizeOf(field_info.type) != 0) {
                     const field = @intToEnum(Field, i);
-                    mem.copy(field_info.type, result_slice.items(field), self_slice.items(field));
+                    @memcpy(result_slice.items(field), self_slice.items(field));
                 }
             }
             return result;
diff --git a/lib/std/net.zig b/lib/std/net.zig
index d59676ec17..15a9e01da8 100644
--- a/lib/std/net.zig
+++ b/lib/std/net.zig
@@ -106,8 +106,8 @@ pub const Address = extern union {
         // Add 1 to ensure a terminating 0 is present in the path array for maximum portability.
         if (path.len + 1 > sock_addr.path.len) return error.NameTooLong;
 
-        mem.set(u8, &sock_addr.path, 0);
-        mem.copy(u8, &sock_addr.path, path);
+        @memset(&sock_addr.path, 0);
+        @memcpy(sock_addr.path[0..path.len], path);
 
         return Address{ .un = sock_addr };
     }
@@ -346,7 +346,7 @@ pub const Ip6Address = extern struct {
                 if (!saw_any_digits) {
                     if (abbrv) return error.InvalidCharacter; // ':::'
                     if (i != 0) abbrv = true;
-                    mem.set(u8, ip_slice[index..], 0);
+                    @memset(ip_slice[index..], 0);
                     ip_slice = tail[0..];
                     index = 0;
                     continue;
@@ -416,7 +416,7 @@ pub const Ip6Address = extern struct {
             index += 1;
             ip_slice[index] = @truncate(u8, x);
             index += 1;
-            mem.copy(u8, result.sa.addr[16 - index ..], ip_slice[0..index]);
+            @memcpy(result.sa.addr[16 - index ..][0..index], ip_slice[0..index]);
             return result;
         }
     }
@@ -465,7 +465,7 @@ pub const Ip6Address = extern struct {
                 if (!saw_any_digits) {
                     if (abbrv) return error.InvalidCharacter; // ':::'
                     if (i != 0) abbrv = true;
-                    mem.set(u8, ip_slice[index..], 0);
+                    @memset(ip_slice[index..], 0);
                     ip_slice = tail[0..];
                     index = 0;
                     continue;
@@ -550,7 +550,7 @@ pub const Ip6Address = extern struct {
             index += 1;
             ip_slice[index] = @truncate(u8, x);
             index += 1;
-            mem.copy(u8, result.sa.addr[16 - index ..], ip_slice[0..index]);
+            @memcpy(result.sa.addr[16 - index ..][0..index], ip_slice[0..index]);
             return result;
         }
     }
@@ -662,7 +662,7 @@ fn if_nametoindex(name: []const u8) !u32 {
         var sockfd = try os.socket(os.AF.UNIX, os.SOCK.DGRAM | os.SOCK.CLOEXEC, 0);
         defer os.closeSocket(sockfd);
 
-        std.mem.copy(u8, &ifr.ifrn.name, name);
+        @memcpy(ifr.ifrn.name[0..name.len], name);
         ifr.ifrn.name[name.len] = 0;
 
         // TODO investigate if this needs to be integrated with evented I/O.
@@ -676,7 +676,7 @@ fn if_nametoindex(name: []const u8) !u32 {
             return error.NameTooLong;
 
         var if_name: [os.IFNAMESIZE:0]u8 = undefined;
-        std.mem.copy(u8, &if_name, name);
+        @memcpy(if_name[0..name.len], name);
         if_name[name.len] = 0;
         const if_slice = if_name[0..name.len :0];
         const index = os.system.if_nametoindex(if_slice);
@@ -1041,14 +1041,14 @@ fn linuxLookupName(
         var salen: os.socklen_t = undefined;
         var dalen: os.socklen_t = undefined;
         if (addr.addr.any.family == os.AF.INET6) {
-            mem.copy(u8, &da6.addr, &addr.addr.in6.sa.addr);
+            da6.addr = addr.addr.in6.sa.addr;
             da = @ptrCast(*os.sockaddr, &da6);
             dalen = @sizeOf(os.sockaddr.in6);
             sa = @ptrCast(*os.sockaddr, &sa6);
             salen = @sizeOf(os.sockaddr.in6);
         } else {
-            mem.copy(u8, &sa6.addr, "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff");
-            mem.copy(u8, &da6.addr, "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff");
+            sa6.addr[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
+            da6.addr[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
             mem.writeIntNative(u32, da6.addr[12..], addr.addr.in.sa.addr);
             da4.addr = addr.addr.in.sa.addr;
             da = @ptrCast(*os.sockaddr, &da4);
@@ -1343,7 +1343,7 @@ fn linuxLookupNameFromDnsSearch(
     // name is not a CNAME record) and serves as a buffer for passing
     // the full requested name to name_from_dns.
     try canon.resize(canon_name.len);
-    mem.copy(u8, canon.items, canon_name);
+    @memcpy(canon.items, canon_name);
     try canon.append('.');
 
     var tok_it = mem.tokenize(u8, search, " \t");
@@ -1567,7 +1567,7 @@ fn resMSendRc(
         for (0..ns.len) |i| {
             if (ns[i].any.family != os.AF.INET) continue;
             mem.writeIntNative(u32, ns[i].in6.sa.addr[12..], ns[i].in.sa.addr);
-            mem.copy(u8, ns[i].in6.sa.addr[0..12], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff");
+            ns[i].in6.sa.addr[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
             ns[i].any.family = os.AF.INET6;
             ns[i].in6.sa.flowinfo = 0;
             ns[i].in6.sa.scope_id = 0;
@@ -1665,7 +1665,7 @@ fn resMSendRc(
             if (i == next) {
                 while (next < queries.len and answers[next].len != 0) : (next += 1) {}
             } else {
-                mem.copy(u8, answer_bufs[i], answer_bufs[next][0..rlen]);
+                @memcpy(answer_bufs[i][0..rlen], answer_bufs[next][0..rlen]);
             }
 
             if (next == queries.len) break :outer;
diff --git a/lib/std/os.zig b/lib/std/os.zig
index 9a0c05f457..32c73916d4 100644
--- a/lib/std/os.zig
+++ b/lib/std/os.zig
@@ -1881,9 +1881,9 @@ pub fn execvpeZ_expandArg0(
     while (it.next()) |search_path| {
         const path_len = search_path.len + file_slice.len + 1;
         if (path_buf.len < path_len + 1) return error.NameTooLong;
-        mem.copy(u8, &path_buf, search_path);
+        @memcpy(path_buf[0..search_path.len], search_path);
         path_buf[search_path.len] = '/';
-        mem.copy(u8, path_buf[search_path.len + 1 ..], file_slice);
+        @memcpy(path_buf[search_path.len + 1 ..][0..file_slice.len], file_slice);
         path_buf[path_len] = 0;
         const full_path = path_buf[0..path_len :0].ptr;
         switch (arg0_expand) {
@@ -1917,7 +1917,7 @@ pub fn getenv(key: []const u8) ?[]const u8 {
     if (builtin.link_libc) {
         var small_key_buf: [64]u8 = undefined;
         if (key.len < small_key_buf.len) {
-            mem.copy(u8, &small_key_buf, key);
+            @memcpy(small_key_buf[0..key.len], key);
             small_key_buf[key.len] = 0;
             const key0 = small_key_buf[0..key.len :0];
             return getenvZ(key0);
@@ -2022,8 +2022,9 @@ pub fn getcwd(out_buffer: []u8) GetCwdError![]u8 {
     } else if (builtin.os.tag == .wasi and !builtin.link_libc) {
         const path = ".";
         if (out_buffer.len < path.len) return error.NameTooLong;
-        std.mem.copy(u8, out_buffer, path);
-        return out_buffer[0..path.len];
+        const result = out_buffer[0..path.len];
+        @memcpy(result, path);
+        return result;
     }
 
     const err = if (builtin.link_libc) blk: {
@@ -2673,7 +2674,7 @@ pub fn renameatW(
         .FileNameLength = @intCast(u32, new_path_w.len * 2), // already checked error.NameTooLong
         .FileName = undefined,
     };
-    std.mem.copy(u16, @as([*]u16, &rename_info.FileName)[0..new_path_w.len], new_path_w);
+    @memcpy(@as([*]u16, &rename_info.FileName)[0..new_path_w.len], new_path_w);
 
     var io_status_block: windows.IO_STATUS_BLOCK = undefined;
 
@@ -5264,8 +5265,9 @@ pub fn getFdPath(fd: fd_t, out_buffer: *[MAX_PATH_BYTES]u8) RealPathError![]u8 {
                 }
                 const len = mem.indexOfScalar(u8, &kfile.path, 0) orelse MAX_PATH_BYTES;
                 if (len == 0) return error.NameTooLong;
-                mem.copy(u8, out_buffer, kfile.path[0..len]);
-                return out_buffer[0..len];
+                const result = out_buffer[0..len];
+                @memcpy(result, kfile.path[0..len]);
+                return result;
             } else {
                 // This fallback implementation reimplements libutil's `kinfo_getfile()`.
                 // The motivation is to avoid linking -lutil when building zig or general
@@ -5296,8 +5298,9 @@ pub fn getFdPath(fd: fd_t, out_buffer: *[MAX_PATH_BYTES]u8) RealPathError![]u8 {
                     if (kf.fd == fd) {
                         len = mem.indexOfScalar(u8, &kf.path, 0) orelse MAX_PATH_BYTES;
                         if (len == 0) return error.NameTooLong;
-                        mem.copy(u8, out_buffer, kf.path[0..len]);
-                        return out_buffer[0..len];
+                        const result = out_buffer[0..len];
+                        @memcpy(result, kf.path[0..len]);
+                        return result;
                     }
                     i += @intCast(usize, kf.structsize);
                 }
@@ -5686,8 +5689,9 @@ pub fn gethostname(name_buffer: *[HOST_NAME_MAX]u8) GetHostNameError![]u8 {
     if (builtin.os.tag == .linux) {
         const uts = uname();
         const hostname = mem.sliceTo(&uts.nodename, 0);
-        mem.copy(u8, name_buffer, hostname);
-        return name_buffer[0..hostname.len];
+        const result = name_buffer[0..hostname.len];
+        @memcpy(result, hostname);
+        return result;
     }
 
     @compileError("TODO implement gethostname for this OS");
@@ -5725,7 +5729,7 @@ pub fn res_mkquery(
     @memset(q[0..n], 0);
     q[2] = @as(u8, op) * 8 + 1;
     q[5] = 1;
-    mem.copy(u8, q[13..], name);
+    @memcpy(q[13..][0..name.len], name);
     var i: usize = 13;
     var j: usize = undefined;
     while (q[i] != 0) : (i = j + 1) {
@@ -5748,7 +5752,7 @@ pub fn res_mkquery(
     q[0] = @truncate(u8, id / 256);
     q[1] = @truncate(u8, id);
 
-    mem.copy(u8, buf, q[0..n]);
+    @memcpy(buf[0..n], q[0..n]);
     return n;
 }
 
@@ -6755,7 +6759,7 @@ fn toMemFdPath(name: []const u8) ![MFD_MAX_NAME_LEN:0]u8 {
     var path_with_null: [MFD_MAX_NAME_LEN:0]u8 = undefined;
     // >= rather than > to make room for the null byte
     if (name.len >= MFD_MAX_NAME_LEN) return error.NameTooLong;
-    mem.copy(u8, &path_with_null, name);
+    @memcpy(path_with_null[0..name.len], name);
     path_with_null[name.len] = 0;
     return path_with_null;
 }
diff --git a/lib/std/os/linux/bpf.zig b/lib/std/os/linux/bpf.zig
index db6473d673..63b669acd5 100644
--- a/lib/std/os/linux/bpf.zig
+++ b/lib/std/os/linux/bpf.zig
@@ -1631,7 +1631,7 @@ test "map lookup, update, and delete" {
     const status = try map_get_next_key(map, &lookup_key, &next_key);
     try expectEqual(status, true);
     try expectEqual(next_key, key);
-    std.mem.copy(u8, &lookup_key, &next_key);
+    lookup_key = next_key;
     const status2 = try map_get_next_key(map, &lookup_key, &next_key);
     try expectEqual(status2, false);
 
diff --git a/lib/std/os/linux/io_uring.zig b/lib/std/os/linux/io_uring.zig
index 20248fd65f..b7467d765f 100644
--- a/lib/std/os/linux/io_uring.zig
+++ b/lib/std/os/linux/io_uring.zig
@@ -1855,8 +1855,8 @@ test "write_fixed/read_fixed" {
 
     var raw_buffers: [2][11]u8 = undefined;
     // First buffer will be written to the file.
-    std.mem.set(u8, &raw_buffers[0], 'z');
-    std.mem.copy(u8, &raw_buffers[0], "foobar");
+    @memset(&raw_buffers[0], 'z');
+    raw_buffers[0][0.."foobar".len].* = "foobar".*;
 
     var buffers = [2]os.iovec{
         .{ .iov_base = &raw_buffers[0], .iov_len = raw_buffers[0].len },
@@ -2966,7 +2966,7 @@ test "provide_buffers: read" {
     // Provide 1 buffer again
 
     // Deliberately put something we don't expect in the buffers
-    mem.set(u8, mem.sliceAsBytes(&buffers), 42);
+    @memset(mem.sliceAsBytes(&buffers), 42);
 
     const reprovided_buffer_id = 2;
 
@@ -3155,7 +3155,7 @@ test "provide_buffers: accept/connect/send/recv" {
     // Do 4 recv which should consume all buffers
 
     // Deliberately put something we don't expect in the buffers
-    mem.set(u8, mem.sliceAsBytes(&buffers), 1);
+    @memset(mem.sliceAsBytes(&buffers), 1);
 
     var i: usize = 0;
     while (i < buffers.len) : (i += 1) {
@@ -3235,7 +3235,7 @@ test "provide_buffers: accept/connect/send/recv" {
     // Final recv which should work
 
     // Deliberately put something we don't expect in the buffers
-    mem.set(u8, mem.sliceAsBytes(&buffers), 1);
+    @memset(mem.sliceAsBytes(&buffers), 1);
 
     {
         var sqe = try ring.recv(0xdfdfdfdf, socket_test_harness.client, .{ .buffer_selection = .{ .group_id = group_id, .len = buffer_len } }, 0);
diff --git a/lib/std/os/linux/tls.zig b/lib/std/os/linux/tls.zig
index cffdec0424..311e5609e8 100644
--- a/lib/std/os/linux/tls.zig
+++ b/lib/std/os/linux/tls.zig
@@ -275,7 +275,7 @@ inline fn alignPtrCast(comptime T: type, ptr: [*]u8) *T {
 /// architecture-specific value of the thread-pointer register
 pub fn prepareTLS(area: []u8) usize {
     // Clear the area we're going to use, just to be safe
-    mem.set(u8, area, 0);
+    @memset(area, 0);
     // Prepare the DTV
     const dtv = alignPtrCast(DTV, area.ptr + tls_image.dtv_offset);
     dtv.entries = 1;
@@ -287,7 +287,7 @@ pub fn prepareTLS(area: []u8) usize {
         .VariantII => area.ptr + tls_image.tcb_offset,
     };
     // Copy the data
-    mem.copy(u8, area[tls_image.data_offset..], tls_image.init_data);
+    @memcpy(area[tls_image.data_offset..][0..tls_image.init_data.len], tls_image.init_data);
 
     // Return the corrected value (if needed) for the tp register.
     // Overflow here is not a problem, the pointer arithmetic involving the tp
diff --git a/lib/std/os/test.zig b/lib/std/os/test.zig
index 682bd4f6f8..f694ea277a 100644
--- a/lib/std/os/test.zig
+++ b/lib/std/os/test.zig
@@ -587,7 +587,7 @@ test "mmap" {
         try testing.expect(mem.eql(u8, data, &[_]u8{0x00} ** 1234));
 
         // Make sure the memory is writeable as requested
-        std.mem.set(u8, data, 0x55);
+        @memset(data, 0x55);
         try testing.expect(mem.eql(u8, data, &[_]u8{0x55} ** 1234));
     }
 
diff --git a/lib/std/os/uefi/protocols/device_path_protocol.zig b/lib/std/os/uefi/protocols/device_path_protocol.zig
index fb497a79da..2365b0cb2e 100644
--- a/lib/std/os/uefi/protocols/device_path_protocol.zig
+++ b/lib/std/os/uefi/protocols/device_path_protocol.zig
@@ -48,7 +48,7 @@ pub const DevicePathProtocol = extern struct {
         // DevicePathProtocol for the extra node before the end
         var buf = try allocator.alloc(u8, path_size + 2 * (path.len + 1) + @sizeOf(DevicePathProtocol));
 
-        mem.copy(u8, buf, @ptrCast([*]const u8, self)[0..path_size]);
+        @memcpy(buf[0..path_size.len], @ptrCast([*]const u8, self)[0..path_size]);
 
         // Pointer to the copy of the end node of the current chain, which is - 4 from the buffer
         // as the end node itself is 4 bytes (type: u8 + subtype: u8 + length: u16).
diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index 23139c9f92..6d654f1c20 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -754,7 +754,7 @@ pub fn CreateSymbolicLink(
         .Flags = if (dir) |_| SYMLINK_FLAG_RELATIVE else 0,
     };
 
-    std.mem.copy(u8, buffer[0..], std.mem.asBytes(&symlink_data));
+    @memcpy(buffer[0..@sizeOf(SYMLINK_DATA)], std.mem.asBytes(&symlink_data));
     @memcpy(buffer[@sizeOf(SYMLINK_DATA)..][0 .. target_path.len * 2], @ptrCast([*]const u8, target_path));
     const paths_start = @sizeOf(SYMLINK_DATA) + target_path.len * 2;
     @memcpy(buffer[paths_start..][0 .. target_path.len * 2], @ptrCast([*]const u8, target_path));
@@ -1208,8 +1208,8 @@ pub fn GetFinalPathNameByHandle(
 
                     if (out_buffer.len < drive_letter.len + file_name_u16.len) return error.NameTooLong;
 
-                    mem.copy(u16, out_buffer, drive_letter);
-                    mem.copy(u16, out_buffer[drive_letter.len..], file_name_u16);
+                    @memcpy(out_buffer[0..drive_letter.len], drive_letter);
+                    mem.copyForwards(u16, out_buffer[drive_letter.len..][0..file_name_u16.len], file_name_u16);
                     const total_len = drive_letter.len + file_name_u16.len;
 
                     // Validate that DOS does not contain any spurious nul bytes.
@@ -2012,7 +2012,7 @@ pub fn sliceToPrefixedFileW(s: []const u8) !PathSpace {
     }
     const prefix_u16 = [_]u16{ '\\', '?', '?', '\\' };
     const start_index = if (prefix_index > 0 or !std.fs.path.isAbsolute(s)) 0 else blk: {
-        mem.copy(u16, path_space.data[0..], prefix_u16[0..]);
+        path_space.data[0..prefix_u16.len].* = prefix_u16;
         break :blk prefix_u16.len;
     };
     path_space.len = start_index + try std.unicode.utf8ToUtf16Le(path_space.data[start_index..], s);
@@ -2025,7 +2025,7 @@ pub fn sliceToPrefixedFileW(s: []const u8) !PathSpace {
                 std.debug.assert(temp_path.len == path_space.len);
                 temp_path.data[path_space.len] = 0;
                 path_space.len = prefix_u16.len + try getFullPathNameW(&temp_path.data, path_space.data[prefix_u16.len..]);
-                mem.copy(u16, &path_space.data, &prefix_u16);
+                path_space.data[0..prefix_u16.len].* = prefix_u16;
                 std.debug.assert(path_space.data[path_space.len] == 0);
                 return path_space;
             }
@@ -2053,12 +2053,12 @@ pub fn wToPrefixedFileW(s: []const u16) !PathSpace {
 
     const start_index = if (mem.startsWith(u16, s, &[_]u16{ '\\', '?' })) 0 else blk: {
         const prefix = [_]u16{ '\\', '?', '?', '\\' };
-        mem.copy(u16, path_space.data[0..], &prefix);
+        path_space.data[0..prefix.len].* = prefix;
         break :blk prefix.len;
     };
     path_space.len = start_index + s.len;
     if (path_space.len > path_space.data.len) return error.NameTooLong;
-    mem.copy(u16, path_space.data[start_index..], s);
+    @memcpy(path_space.data[start_index..][0..s.len], s);
     // > File I/O functions in the Windows API convert "/" to "\" as part of
     // > converting the name to an NT-style name, except when using the "\\?\"
     // > prefix as detailed in the following sections.
diff --git a/lib/std/process.zig b/lib/std/process.zig
index 56e3708f3b..504f9075eb 100644
--- a/lib/std/process.zig
+++ b/lib/std/process.zig
@@ -855,7 +855,7 @@ pub fn argsAlloc(allocator: Allocator) ![][:0]u8 {
 
     const result_slice_list = mem.bytesAsSlice([:0]u8, buf[0..slice_list_bytes]);
     const result_contents = buf[slice_list_bytes..];
-    mem.copy(u8, result_contents, contents_slice);
+    @memcpy(result_contents[0..contents_slice.len], contents_slice);
 
     var contents_index: usize = 0;
     for (slice_sizes, 0..) |len, i| {
diff --git a/lib/std/rand/ChaCha.zig b/lib/std/rand/ChaCha.zig
index 0992aeb97e..3878fb25c8 100644
--- a/lib/std/rand/ChaCha.zig
+++ b/lib/std/rand/ChaCha.zig
@@ -40,7 +40,8 @@ pub fn addEntropy(self: *Self, bytes: []const u8) void {
     }
     if (i < bytes.len) {
         var k = [_]u8{0} ** Cipher.key_length;
-        mem.copy(u8, k[0..], bytes[i..]);
+        const src = bytes[i..];
+        @memcpy(k[0..src.len], src);
         Cipher.xor(
             self.state[0..Cipher.key_length],
             self.state[0..Cipher.key_length],
@@ -72,8 +73,8 @@ pub fn fill(self: *Self, buf_: []u8) void {
     if (avail > 0) {
         // Bytes from the current block
         const n = @min(avail, buf.len);
-        mem.copy(u8, buf[0..n], bytes[self.offset..][0..n]);
-        mem.set(u8, bytes[self.offset..][0..n], 0);
+        @memcpy(buf[0..n], bytes[self.offset..][0..n]);
+        @memset(bytes[self.offset..][0..n], 0);
         buf = buf[n..];
         self.offset += n;
     }
@@ -83,15 +84,15 @@ pub fn fill(self: *Self, buf_: []u8) void {
 
     // Full blocks
     while (buf.len >= bytes.len) {
-        mem.copy(u8, buf[0..bytes.len], bytes);
+        @memcpy(buf[0..bytes.len], bytes);
         buf = buf[bytes.len..];
         self.refill();
     }
 
     // Remaining bytes
     if (buf.len > 0) {
-        mem.copy(u8, buf, bytes[0..buf.len]);
-        mem.set(u8, bytes[0..buf.len], 0);
+        @memcpy(buf, bytes[0..buf.len]);
+        @memset(bytes[0..buf.len], 0);
         self.offset = buf.len;
     }
 }
diff --git a/lib/std/rand/Isaac64.zig b/lib/std/rand/Isaac64.zig
index 42242008fc..8c6205e1cd 100644
--- a/lib/std/rand/Isaac64.zig
+++ b/lib/std/rand/Isaac64.zig
@@ -87,7 +87,7 @@ fn next(self: *Isaac64) u64 {
 fn seed(self: *Isaac64, init_s: u64, comptime rounds: usize) void {
     // We ignore the multi-pass requirement since we don't currently expose full access to
     // seeding the self.m array completely.
-    mem.set(u64, self.m[0..], 0);
+    @memset(self.m[0..], 0);
     self.m[0] = init_s;
 
     // prescrambled golden ratio constants
@@ -143,7 +143,7 @@ fn seed(self: *Isaac64, init_s: u64, comptime rounds: usize) void {
         }
     }
 
-    mem.set(u64, self.r[0..], 0);
+    @memset(self.r[0..], 0);
     self.a = 0;
     self.b = 0;
     self.c = 0;
diff --git a/lib/std/segmented_list.zig b/lib/std/segmented_list.zig
index 7c0a27b5b7..172fe4e7c3 100644
--- a/lib/std/segmented_list.zig
+++ b/lib/std/segmented_list.zig
@@ -230,7 +230,7 @@ pub fn SegmentedList(comptime T: type, comptime prealloc_item_count: usize) type
                 allocator.free(new_dynamic_segments);
             } else {
                 // Good thing we allocated that new memory slice.
-                mem.copy([*]T, new_dynamic_segments, self.dynamic_segments[0..new_cap_shelf_count]);
+                @memcpy(new_dynamic_segments, self.dynamic_segments[0..new_cap_shelf_count]);
                 allocator.free(self.dynamic_segments);
                 self.dynamic_segments = new_dynamic_segments;
             }
@@ -248,24 +248,21 @@ pub fn SegmentedList(comptime T: type, comptime prealloc_item_count: usize) type
 
             var i = start;
             if (end <= prealloc_item_count) {
-                mem.copy(T, dest[i - start ..], self.prealloc_segment[i..end]);
+                const src = self.prealloc_segment[i..end];
+                @memcpy(dest[i - start ..][0..src.len], src);
                 return;
             } else if (i < prealloc_item_count) {
-                mem.copy(T, dest[i - start ..], self.prealloc_segment[i..]);
+                const src = self.prealloc_segment[i..];
+                @memcpy(dest[i - start ..][0..src.len], src);
                 i = prealloc_item_count;
             }
 
             while (i < end) {
                 const shelf_index = shelfIndex(i);
                 const copy_start = boxIndex(i, shelf_index);
-                const copy_end = std.math.min(shelfSize(shelf_index), copy_start + end - i);
-
-                mem.copy(
-                    T,
-                    dest[i - start ..],
-                    self.dynamic_segments[shelf_index][copy_start..copy_end],
-                );
-
+                const copy_end = @min(shelfSize(shelf_index), copy_start + end - i);
+                const src = self.dynamic_segments[shelf_index][copy_start..copy_end];
+                @memcpy(dest[i - start ..][0..src.len], src);
                 i += (copy_end - copy_start);
             }
         }
@@ -498,11 +495,11 @@ fn testSegmentedList(comptime prealloc: usize) !void {
             control[@intCast(usize, i)] = i + 1;
         }
 
-        mem.set(i32, dest[0..], 0);
+        @memset(dest[0..], 0);
         list.writeToSlice(dest[0..], 0);
         try testing.expect(mem.eql(i32, control[0..], dest[0..]));
 
-        mem.set(i32, dest[0..], 0);
+        @memset(dest[0..], 0);
         list.writeToSlice(dest[50..], 50);
         try testing.expect(mem.eql(i32, control[50..], dest[50..]));
     }
diff --git a/lib/std/sort.zig b/lib/std/sort.zig
index d2b79db91b..080ab5200e 100644
--- a/lib/std/sort.zig
+++ b/lib/std/sort.zig
@@ -361,8 +361,10 @@ pub fn sort(
 
                     if (lessThan(context, items[B1.end - 1], items[A1.start])) {
                         // the two ranges are in reverse order, so copy them in reverse order into the cache
-                        mem.copy(T, cache[B1.length()..], items[A1.start..A1.end]);
-                        mem.copy(T, cache[0..], items[B1.start..B1.end]);
+                        const a1_items = items[A1.start..A1.end];
+                        @memcpy(cache[B1.length()..][0..a1_items.len], a1_items);
+                        const b1_items = items[B1.start..B1.end];
+                        @memcpy(cache[0..b1_items.len], b1_items);
                     } else if (lessThan(context, items[B1.start], items[A1.end - 1])) {
                         // these two ranges weren't already in order, so merge them into the cache
                         mergeInto(T, items, A1, B1, context, lessThan, cache[0..]);
@@ -371,23 +373,29 @@ pub fn sort(
                         if (!lessThan(context, items[B2.start], items[A2.end - 1]) and !lessThan(context, items[A2.start], items[B1.end - 1])) continue;
 
                         // copy A1 and B1 into the cache in the same order
-                        mem.copy(T, cache[0..], items[A1.start..A1.end]);
-                        mem.copy(T, cache[A1.length()..], items[B1.start..B1.end]);
+                        const a1_items = items[A1.start..A1.end];
+                        @memcpy(cache[0..a1_items.len], a1_items);
+                        const b1_items = items[B1.start..B1.end];
+                        @memcpy(cache[A1.length()..][0..b1_items.len], b1_items);
                     }
                     A1 = Range.init(A1.start, B1.end);
 
                     // merge A2 and B2 into the cache
                     if (lessThan(context, items[B2.end - 1], items[A2.start])) {
                         // the two ranges are in reverse order, so copy them in reverse order into the cache
-                        mem.copy(T, cache[A1.length() + B2.length() ..], items[A2.start..A2.end]);
-                        mem.copy(T, cache[A1.length()..], items[B2.start..B2.end]);
+                        const a2_items = items[A2.start..A2.end];
+                        @memcpy(cache[A1.length() + B2.length() ..][0..a2_items.len], a2_items);
+                        const b2_items = items[B2.start..B2.end];
+                        @memcpy(cache[A1.length()..][0..b2_items.len], b2_items);
                     } else if (lessThan(context, items[B2.start], items[A2.end - 1])) {
                         // these two ranges weren't already in order, so merge them into the cache
                         mergeInto(T, items, A2, B2, context, lessThan, cache[A1.length()..]);
                     } else {
                         // copy A2 and B2 into the cache in the same order
-                        mem.copy(T, cache[A1.length()..], items[A2.start..A2.end]);
-                        mem.copy(T, cache[A1.length() + A2.length() ..], items[B2.start..B2.end]);
+                        const a2_items = items[A2.start..A2.end];
+                        @memcpy(cache[A1.length()..][0..a2_items.len], a2_items);
+                        const b2_items = items[B2.start..B2.end];
+                        @memcpy(cache[A1.length() + A2.length() ..][0..b2_items.len], b2_items);
                     }
                     A2 = Range.init(A2.start, B2.end);
 
@@ -397,15 +405,19 @@ pub fn sort(
 
                     if (lessThan(context, cache[B3.end - 1], cache[A3.start])) {
                         // the two ranges are in reverse order, so copy them in reverse order into the items
-                        mem.copy(T, items[A1.start + A2.length() ..], cache[A3.start..A3.end]);
-                        mem.copy(T, items[A1.start..], cache[B3.start..B3.end]);
+                        const a3_items = cache[A3.start..A3.end];
+                        @memcpy(items[A1.start + A2.length() ..][0..a3_items.len], a3_items);
+                        const b3_items = cache[B3.start..B3.end];
+                        @memcpy(items[A1.start..][0..b3_items.len], b3_items);
                     } else if (lessThan(context, cache[B3.start], cache[A3.end - 1])) {
                         // these two ranges weren't already in order, so merge them back into the items
                         mergeInto(T, cache[0..], A3, B3, context, lessThan, items[A1.start..]);
                     } else {
                         // copy A3 and B3 into the items in the same order
-                        mem.copy(T, items[A1.start..], cache[A3.start..A3.end]);
-                        mem.copy(T, items[A1.start + A1.length() ..], cache[B3.start..B3.end]);
+                        const a3_items = cache[A3.start..A3.end];
+                        @memcpy(items[A1.start..][0..a3_items.len], a3_items);
+                        const b3_items = cache[B3.start..B3.end];
+                        @memcpy(items[A1.start + A1.length() ..][0..b3_items.len], b3_items);
                     }
                 }
 
@@ -423,7 +435,8 @@ pub fn sort(
                         mem.rotate(T, items[A.start..B.end], A.length());
                     } else if (lessThan(context, items[B.start], items[A.end - 1])) {
                         // these two ranges weren't already in order, so we'll need to merge them!
-                        mem.copy(T, cache[0..], items[A.start..A.end]);
+                        const a_items = items[A.start..A.end];
+                        @memcpy(cache[0..a_items.len], a_items);
                         mergeExternal(T, items, A, B, context, lessThan, cache[0..]);
                     }
                 }
@@ -718,7 +731,8 @@ pub fn sort(
                     // if the first unevenly sized A block fits into the cache, copy it there for when we go to Merge it
                     // otherwise, if the second buffer is available, block swap the contents into that
                     if (lastA.length() <= cache.len) {
-                        mem.copy(T, cache[0..], items[lastA.start..lastA.end]);
+                        const last_a_items = items[lastA.start..lastA.end];
+                        @memcpy(cache[0..last_a_items.len], last_a_items);
                     } else if (buffer2.length() > 0) {
                         blockSwap(T, items, lastA.start, buffer2.start, lastA.length());
                     }
@@ -762,7 +776,7 @@ pub fn sort(
                                 if (buffer2.length() > 0 or block_size <= cache.len) {
                                     // copy the previous A block into the cache or buffer2, since that's where we need it to be when we go to merge it anyway
                                     if (block_size <= cache.len) {
-                                        mem.copy(T, cache[0..], items[blockA.start .. blockA.start + block_size]);
+                                        @memcpy(cache[0..block_size], items[blockA.start..][0..block_size]);
                                     } else {
                                         blockSwap(T, items, blockA.start, buffer2.start, block_size);
                                     }
@@ -1122,7 +1136,8 @@ fn mergeInto(
             insert_index += 1;
             if (A_index == A_last) {
                 // copy the remainder of B into the final array
-                mem.copy(T, into[insert_index..], from[B_index..B_last]);
+                const from_b = from[B_index..B_last];
+                @memcpy(into[insert_index..][0..from_b.len], from_b);
                 break;
             }
         } else {
@@ -1131,7 +1146,8 @@ fn mergeInto(
             insert_index += 1;
             if (B_index == B_last) {
                 // copy the remainder of A into the final array
-                mem.copy(T, into[insert_index..], from[A_index..A_last]);
+                const from_a = from[A_index..A_last];
+                @memcpy(into[insert_index..][0..from_a.len], from_a);
                 break;
             }
         }
@@ -1171,7 +1187,8 @@ fn mergeExternal(
     }
 
     // copy the remainder of A into the final array
-    mem.copy(T, items[insert_index..], cache[A_index..A_last]);
+    const cache_a = cache[A_index..A_last];
+    @memcpy(items[insert_index..][0..cache_a.len], cache_a);
 }
 
 fn swap(
@@ -1305,7 +1322,7 @@ test "sort" {
     for (u8cases) |case| {
         var buf: [8]u8 = undefined;
         const slice = buf[0..case[0].len];
-        mem.copy(u8, slice, case[0]);
+        @memcpy(slice, case[0]);
         sort(u8, slice, {}, asc_u8);
         try testing.expect(mem.eql(u8, slice, case[1]));
     }
@@ -1340,7 +1357,7 @@ test "sort" {
     for (i32cases) |case| {
         var buf: [8]i32 = undefined;
         const slice = buf[0..case[0].len];
-        mem.copy(i32, slice, case[0]);
+        @memcpy(slice, case[0]);
         sort(i32, slice, {}, asc_i32);
         try testing.expect(mem.eql(i32, slice, case[1]));
     }
@@ -1377,7 +1394,7 @@ test "sort descending" {
     for (rev_cases) |case| {
         var buf: [8]i32 = undefined;
         const slice = buf[0..case[0].len];
-        mem.copy(i32, slice, case[0]);
+        @memcpy(slice, case[0]);
         sort(i32, slice, {}, desc_i32);
         try testing.expect(mem.eql(i32, slice, case[1]));
     }
diff --git a/lib/std/tar.zig b/lib/std/tar.zig
index ec668d5f93..c570c8e09c 100644
--- a/lib/std/tar.zig
+++ b/lib/std/tar.zig
@@ -55,9 +55,9 @@ pub const Header = struct {
         const p = prefix(header);
         if (p.len == 0)
             return n;
-        std.mem.copy(u8, buffer[0..p.len], p);
+        @memcpy(buffer[0..p.len], p);
         buffer[p.len] = '/';
-        std.mem.copy(u8, buffer[p.len + 1 ..], n);
+        @memcpy(buffer[p.len + 1 ..][0..n.len], n);
         return buffer[0 .. p.len + 1 + n.len];
     }
 
@@ -101,8 +101,9 @@ pub fn pipeToFileSystem(dir: std.fs.Dir, reader: anytype, options: Options) !voi
     var end: usize = 0;
     header: while (true) {
         if (buffer.len - start < 1024) {
-            std.mem.copy(u8, &buffer, buffer[start..end]);
-            end -= start;
+            const dest_end = end - start;
+            @memcpy(buffer[0..dest_end], buffer[start..end]);
+            end = dest_end;
             start = 0;
         }
         const ask_header = @min(buffer.len - end, 1024 -| (end - start));
@@ -138,8 +139,9 @@ pub fn pipeToFileSystem(dir: std.fs.Dir, reader: anytype, options: Options) !voi
                 var file_off: usize = 0;
                 while (true) {
                     if (buffer.len - start < 1024) {
-                        std.mem.copy(u8, &buffer, buffer[start..end]);
-                        end -= start;
+                        const dest_end = end - start;
+                        @memcpy(buffer[0..dest_end], buffer[start..end]);
+                        end = dest_end;
                         start = 0;
                     }
                     // Ask for the rounded up file size + 512 for the next header.
diff --git a/lib/std/target.zig b/lib/std/target.zig
index d9214f7be6..f23e32fbe7 100644
--- a/lib/std/target.zig
+++ b/lib/std/target.zig
@@ -1596,7 +1596,7 @@ pub const Target = struct {
         /// Asserts that the length is less than or equal to 255 bytes.
         pub fn set(self: *DynamicLinker, dl_or_null: ?[]const u8) void {
             if (dl_or_null) |dl| {
-                mem.copy(u8, &self.buffer, dl);
+                @memcpy(self.buffer[0..dl.len], dl);
                 self.max_byte = @intCast(u8, dl.len - 1);
             } else {
                 self.max_byte = null;
@@ -1612,7 +1612,7 @@ pub const Target = struct {
                 return r.*;
             }
             fn copy(r: *DynamicLinker, s: []const u8) DynamicLinker {
-                mem.copy(u8, &r.buffer, s);
+                @memcpy(r.buffer[0..s.len], s);
                 r.max_byte = @intCast(u8, s.len - 1);
                 return r.*;
             }
diff --git a/lib/std/testing/failing_allocator.zig b/lib/std/testing/failing_allocator.zig
index 914e405b11..2cdb78cd1d 100644
--- a/lib/std/testing/failing_allocator.zig
+++ b/lib/std/testing/failing_allocator.zig
@@ -66,7 +66,7 @@ pub const FailingAllocator = struct {
         const self = @ptrCast(*FailingAllocator, @alignCast(@alignOf(FailingAllocator), ctx));
         if (self.index == self.fail_index) {
             if (!self.has_induced_failure) {
-                mem.set(usize, &self.stack_addresses, 0);
+                @memset(&self.stack_addresses, 0);
                 var stack_trace = std.builtin.StackTrace{
                     .instruction_addresses = &self.stack_addresses,
                     .index = 0,
diff --git a/lib/std/tz.zig b/lib/std/tz.zig
index 76eb3b06fc..0cb9cefa50 100644
--- a/lib/std/tz.zig
+++ b/lib/std/tz.zig
@@ -137,7 +137,7 @@ pub const Tz = struct {
             const name = std.mem.sliceTo(designators[tt.name_data[0]..], 0);
             // We are mandating the "SHOULD" 6-character limit so we can pack the struct better, and to conform to POSIX.
             if (name.len > 6) return error.Malformed; // rfc8536: Time zone designations SHOULD consist of at least three (3) and no more than six (6) ASCII characters.
-            std.mem.copy(u8, tt.name_data[0..], name);
+            @memcpy(tt.name_data[0..name.len], name);
             tt.name_data[name.len] = 0;
         }
 
diff --git a/lib/std/zig/render.zig b/lib/std/zig/render.zig
index 2cb1d170b4..d8a8c8e9ed 100644
--- a/lib/std/zig/render.zig
+++ b/lib/std/zig/render.zig
@@ -1889,11 +1889,11 @@ fn renderArrayInit(
         // A place to store the width of each expression and its column's maximum
         const widths = try gpa.alloc(usize, row_exprs.len + row_size);
         defer gpa.free(widths);
-        mem.set(usize, widths, 0);
+        @memset(widths, 0);
 
         const expr_newlines = try gpa.alloc(bool, row_exprs.len);
         defer gpa.free(expr_newlines);
-        mem.set(bool, expr_newlines, false);
+        @memset(expr_newlines, false);
 
         const expr_widths = widths[0..row_exprs.len];
         const column_widths = widths[row_exprs.len..];
diff --git a/lib/std/zig/system/NativeTargetInfo.zig b/lib/std/zig/system/NativeTargetInfo.zig
index 987358ed5a..539ad96365 100644
--- a/lib/std/zig/system/NativeTargetInfo.zig
+++ b/lib/std/zig/system/NativeTargetInfo.zig
@@ -877,17 +877,17 @@ pub fn abiAndDynamicLinkerFromFile(
         const cpu_arch = @tagName(result.target.cpu.arch);
         const os_tag = @tagName(result.target.os.tag);
         const abi = @tagName(result.target.abi);
-        mem.copy(u8, path_buf[index..], prefix);
+        @memcpy(path_buf[index..][0..prefix.len], prefix);
         index += prefix.len;
-        mem.copy(u8, path_buf[index..], cpu_arch);
+        @memcpy(path_buf[index..][0..cpu_arch.len], cpu_arch);
         index += cpu_arch.len;
         path_buf[index] = '-';
         index += 1;
-        mem.copy(u8, path_buf[index..], os_tag);
+        @memcpy(path_buf[index..][0..os_tag.len], os_tag);
         index += os_tag.len;
         path_buf[index] = '-';
         index += 1;
-        mem.copy(u8, path_buf[index..], abi);
+        @memcpy(path_buf[index..][0..abi.len], abi);
         index += abi.len;
         const rpath = path_buf[0..index];
         if (glibcVerFromRPath(rpath)) |ver| {
diff --git a/lib/std/zig/system/windows.zig b/lib/std/zig/system/windows.zig
index 45b44560a2..6039425b1a 100644
--- a/lib/std/zig/system/windows.zig
+++ b/lib/std/zig/system/windows.zig
@@ -171,10 +171,10 @@ fn getCpuInfoFromRegistry(core: usize, args: anytype) !void {
                     const entry = @ptrCast([*]align(1) const u8, table[i + 1].EntryContext);
                     switch (@field(args, field.name).value_type) {
                         REG.DWORD, REG.DWORD_BIG_ENDIAN => {
-                            mem.copy(u8, @field(args, field.name).value_buf[0..4], entry[0..4]);
+                            @memcpy(@field(args, field.name).value_buf[0..4], entry[0..4]);
                         },
                         REG.QWORD => {
-                            mem.copy(u8, @field(args, field.name).value_buf[0..8], entry[0..8]);
+                            @memcpy(@field(args, field.name).value_buf[0..8], entry[0..8]);
                         },
                         else => unreachable,
                     }