add musl memcpy and avx2 dispatching

crates/compiler/builtins/bitcode/src/libc/cpuid.zig

@@ -0,0 +1,43 @@
+const builtin = @import("builtin");
+const arch = builtin.cpu.arch;
+
+// I couldn't manage to define this in a PIE friendly way with inline assembly.
+// Instead, I am definining it as a global assembly function.
+comptime {
+    switch (arch) {
+        .x86_64 => {
+            asm (
+                \\  # Check if AVX2 is supported.
+                \\  # Returns 1 if AVX2 is supported, 0 otherwise.
+                \\ .global supports_avx2;
+                \\ supports_avx2:
+                \\     # Save the EBX register.
+                \\     push %rbx
+                \\
+                \\     # Call the CPUID instruction with the EAX register set to 7 and ECX set to 0.
+                \\     # This will get the CPUID information for the current CPU.
+                \\     mov $7, %eax
+                \\     mov $0, %ecx
+                \\     cpuid
+                \\
+                \\     # Check if the AVX2 feature flag is set.
+                \\     # The AVX2 feature flag is located in the EBX register at bit 5.
+                \\     bt $5, %ebx
+                \\     jc .AVX2Supported
+                \\
+                \\     # AVX2 is not supported.
+                \\     pop %rbx
+                \\     mov $0, %eax
+                \\     ret
+                \\
+                \\     .AVX2Supported:
+                \\     pop %rbx
+                \\     mov $1, %eax
+                \\     ret
+            );
+        },
+        else => unreachable,
+    }
+}
+
+pub extern fn supports_avx2() bool;