update `@memcpy` to require equal src and dest lens

 * Sema: upgrade operands to array pointers if possible when emitting
   AIR.
 * Implement safety checks for length mismatch and aliasing.
 * AIR: make ptrtoint support slice operands. Implement in LLVM backend.
 * C backend: implement new `@memset` semantics. `@memcpy` is not done
   yet.

4 files changed, 11 insertions, 9 deletions

diff --git a/lib/std/builtin.zig b/lib/std/builtin.zig
index cfe22099cb..048f73482e 100644
--- a/lib/std/builtin.zig
+++ b/lib/std/builtin.zig
@@ -1002,6 +1002,8 @@ pub const panic_messages = struct {
     pub const index_out_of_bounds = "index out of bounds";
     pub const start_index_greater_than_end = "start index is larger than end index";
     pub const for_len_mismatch = "for loop over objects with non-equal lengths";
+    pub const memcpy_len_mismatch = "@memcpy arguments have non-equal lengths";
+    pub const memcpy_alias = "@memcpy arguments alias";
 };
 
 pub noinline fn returnError(st: *StackTrace) void {
diff --git a/lib/std/crypto/aegis.zig b/lib/std/crypto/aegis.zig
index 8cc5a8320e..d7305b444a 100644
--- a/lib/std/crypto/aegis.zig
+++ b/lib/std/crypto/aegis.zig
@@ -209,7 +209,7 @@ fn Aegis128LGeneric(comptime tag_bits: u9) type {
                 acc |= (computed_tag[j] ^ tag[j]);
             }
             if (acc != 0) {
-                @memset(m.ptr, undefined, m.len);
+                @memset(m, undefined);
                 return error.AuthenticationFailed;
             }
         }
@@ -390,7 +390,7 @@ fn Aegis256Generic(comptime tag_bits: u9) type {
                 acc |= (computed_tag[j] ^ tag[j]);
             }
             if (acc != 0) {
-                @memset(m.ptr, undefined, m.len);
+                @memset(m, undefined);
                 return error.AuthenticationFailed;
             }
         }
diff --git a/lib/std/hash/murmur.zig b/lib/std/hash/murmur.zig
index 15fe1b5d7d..95f7c60efe 100644
--- a/lib/std/hash/murmur.zig
+++ b/lib/std/hash/murmur.zig
@@ -99,9 +99,8 @@ pub const Murmur2_64 = struct {
 
     pub fn hashWithSeed(str: []const u8, seed: u64) u64 {
         const m: u64 = 0xc6a4a7935bd1e995;
-        const len = @as(u64, str.len);
-        var h1: u64 = seed ^ (len *% m);
-        for (@ptrCast([*]align(1) const u64, str.ptr)[0..@intCast(usize, len >> 3)]) |v| {
+        var h1: u64 = seed ^ (@as(u64, str.len) *% m);
+        for (@ptrCast([*]align(1) const u64, str.ptr)[0..str.len / 8]) |v| {
             var k1: u64 = v;
             if (native_endian == .Big)
                 k1 = @byteSwap(k1);
@@ -111,11 +110,11 @@ pub const Murmur2_64 = struct {
             h1 ^= k1;
             h1 *%= m;
         }
-        const rest = len & 7;
-        const offset = len - rest;
+        const rest = str.len & 7;
+        const offset = str.len - rest;
         if (rest > 0) {
             var k1: u64 = 0;
-            @memcpy(@ptrCast([*]u8, &k1)[0..@intCast(usize, rest)], @ptrCast([*]const u8, &str[@intCast(usize, offset)]));
+            @memcpy(@ptrCast([*]u8, &k1)[0..rest], str[offset..]);
             if (native_endian == .Big)
                 k1 = @byteSwap(k1);
             h1 ^= k1;
diff --git a/lib/std/mem/Allocator.zig b/lib/std/mem/Allocator.zig
index ce09cd8baa..b402fab3fa 100644
--- a/lib/std/mem/Allocator.zig
+++ b/lib/std/mem/Allocator.zig
@@ -282,7 +282,8 @@ pub fn reallocAdvanced(
 
     const new_mem = self.rawAlloc(byte_count, log2a(Slice.alignment), return_address) orelse
         return error.OutOfMemory;
-    @memcpy(new_mem[0..@min(byte_count, old_byte_slice.len)], old_byte_slice);
+    const copy_len = @min(byte_count, old_byte_slice.len);
+    @memcpy(new_mem[0..copy_len], old_byte_slice[0..copy_len]);
     // TODO https://github.com/ziglang/zig/issues/4298
     @memset(old_byte_slice, undefined);
     self.rawFree(old_byte_slice, log2a(Slice.alignment), return_address);