Enable inline asm on macOS

Author: bjorn3

Readme.md

@@ -52,9 +52,7 @@ configuration options.
 ## Not yet supported
 
 * Inline assembly ([no cranelift support](https://github.com/bytecodealliance/wasmtime/issues/1041))
-    * On Linux there is support for invoking an external assembler for `global_asm!` and `asm!`.
-      `llvm_asm!` will remain unimplemented forever. `asm!` doesn't yet support reg classes. You
-      have to specify specific registers instead.
+    * On UNIX there is support for invoking an external assembler for `global_asm!` and `asm!`.
 * SIMD ([tracked here](https://github.com/bjorn3/rustc_codegen_cranelift/issues/171), some basic things work)
 
 ## License

example/mini_core_hello_world.rs

@@ -321,7 +321,7 @@ fn main() {
     #[cfg(not(any(jit, windows)))]
     test_tls();
 
-    #[cfg(all(not(jit), target_arch = "x86_64", target_os = "linux"))]
+    #[cfg(all(not(jit), target_arch = "x86_64", any(target_os = "linux", target_os = "darwin")))]
     unsafe {
         global_asm_test();
     }
@@ -343,7 +343,7 @@ fn main() {
 }
 }
 
-#[cfg(all(not(jit), target_arch = "x86_64", target_os = "linux"))]
+#[cfg(all(not(jit), target_arch = "x86_64", any(target_os = "linux", target_os = "darwin")))]
 extern "C" {
     fn global_asm_test();
 }
@@ -358,6 +358,16 @@ global_asm! {
     "
 }
 
+#[cfg(all(not(jit), target_arch = "x86_64", target_os = "darwin"))]
+global_asm! {
+    "
+    .global _global_asm_test
+    _global_asm_test:
+    // comment that would normally be removed by LLVM
+    ret
+    "
+}
+
 #[repr(C)]
 enum c_void {
     _1,

src/global_asm.rs

@@ -41,9 +41,7 @@ pub(crate) struct GlobalAsmConfig {
 
 impl GlobalAsmConfig {
     pub(crate) fn new(tcx: TyCtxt<'_>) -> Self {
-        let asm_enabled = cfg!(feature = "inline_asm")
-            && !tcx.sess.target.is_like_osx
-            && !tcx.sess.target.is_like_windows;
+        let asm_enabled = cfg!(feature = "inline_asm") && !tcx.sess.target.is_like_windows;
 
         GlobalAsmConfig {
             asm_enabled,
@@ -74,9 +72,7 @@ pub(crate) fn compile_global_asm(
                     .to_owned(),
             );
         } else {
-            return Err(
-                "asm! and global_asm! are not yet supported on macOS and Windows".to_owned()
-            );
+            return Err("asm! and global_asm! are not yet supported on Windows".to_owned());
         }
     }