[OpenMP] Fix asm for arm64-darwin

[fxcoudert]

Summary

Fixes https://bugs.llvm.org/show_bug.cgi?id=47609

Two issues to be fixed, allowing OpenMP to compile and run on Apple Silicon (arm64-darrwin):

• __kmp_unnamed_criticaladdr needs an extra underscore on Darwin
• the .size should be Linux-only

Both fixes are pretty much the same as the existing X86 and X86_64 Darwin code at the top of that same file.

[Michael_Pique]

Please see discussion D297341 for similar earlier proposal. That patch (D88252: z_Linux_asm.S modifications for arm64 (AARCH64) for Darwin/macOS) incorporated a reviewer suggestion to guard the .size with

#if __ELF__

as more general than

#if KMP_OS_LINUX

That patch was listed as accepted 23 October 2020. Would be good to test both versions on an ARM64 Linux system, but I do not have access to one.

[jdoerfert]

@kiranchandramohan @DavidTruby @richard.barton.arm Could you test this patch and D88252 as described above? I don't have proper setup but you should be able to test all system of interest I assume.

[kiranchandramohan]

I tested with make check-openmp and make check-clang on an AArch64 linux machine and both versions (D91002,D88252) pass.
If you were asking for a different kind of testing then please let me know.

[AndreyChurbanov]

In D91002#2396403, @kiranchandramohan wrote:

I tested with make check-openmp and make check-clang on an AArch64 linux machine and both versions (D91002,D88252) pass.
If you were asking for a different kind of testing then please let me know.

Once the D88252 landed this patch is not needed any more and can be abandoned.

openmp/runtime/src/z_Linux_asm.S

__kmp_unnamed_critical_addr:
     .size __kmp_unnamed_critical_addr,4
 #endif /* KMP_ARCH_ARM */
 
 #if KMP_ARCH_PPC64 || KMP_ARCH_AARCH64 || KMP_ARCH_MIPS64 || KMP_ARCH_RISCV64
     .data
     .comm .gomp_critical_user_,32,8
     .data
     .align 8
-    .global __kmp_unnamed_critical_addr
-__kmp_unnamed_critical_addr:
+    .global KMP_PREFIX_UNDERSCORE(__kmp_unnamed_critical_addr)
+KMP_PREFIX_UNDERSCORE(__kmp_unnamed_critical_addr):
     .8byte .gomp_critical_user_
+# if KMP_OS_LINUX
     .size __kmp_unnamed_critical_addr,8
+# endif /* KMP_OS_LINUX */
 #endif /* KMP_ARCH_PPC64 || KMP_ARCH_AARCH64 || KMP_ARCH_MIPS64 ||
           KMP_ARCH_RISCV64 */
 
 #if KMP_OS_LINUX
 # if KMP_ARCH_ARM
 .section .note.GNU-stack,"",%progbits
 # else
 .section .note.GNU-stack,"",@progbits
 # endif
 #endif