compiler_rt: Move mem implementations from c.zig

This moves functions that LLVM generates calls to,
to the compiler_rt implementation itself, rather than c.zig.
This is a prerequisite for native backends to link with compiler-rt.
This also allows native backends to generate calls to `memcpy` and the like.

1 files changed, 30 insertions, 0 deletions

diff --git a/lib/compiler_rt/memset.zig b/lib/compiler_rt/memset.zig
new file mode 100644
index 0000000000..1b535fee97
--- /dev/null
+++ b/lib/compiler_rt/memset.zig
@@ -0,0 +1,30 @@
+const std = @import("std");
+const common = @import("./common.zig");
+
+comptime {
+    @export(memset, .{ .name = "memset", .linkage = common.linkage });
+    @export(__memset, .{ .name = "__memset", .linkage = common.linkage });
+}
+
+pub fn memset(dest: ?[*]u8, c: u8, len: usize) callconv(.C) ?[*]u8 {
+    @setRuntimeSafety(false);
+
+    if (len != 0) {
+        var d = dest.?;
+        var n = len;
+        while (true) {
+            d[0] = c;
+            n -= 1;
+            if (n == 0) break;
+            d += 1;
+        }
+    }
+
+    return dest;
+}
+
+pub fn __memset(dest: ?[*]u8, c: u8, n: usize, dest_n: usize) callconv(.C) ?[*]u8 {
+    if (dest_n < n)
+        @panic("buffer overflow");
+    return memset(dest, c, n);
+}