[clang] [Preprocessor] Define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 for AArch64 (PR #74954)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Fangrui Song (MaskRay)

<details>
<summary>Changes</summary>

GCC sets `#define HAVE_atomic_compare_and_swapti 1` and therefore
defines `__GCC_HAVE_SYNC_COMPARE_AND_SWAP_16`.

Clang compiles the 16-byte legacy `__sync_bool_compare_and_swap` and new
`__atomic_compare_exchange` compile to LDXP/STXP or (with LSE)
CASP{,A,L,AL}.

Link: https://github.com/llvm/llvm-project/issues/71883


---
Full diff: https://github.com/llvm/llvm-project/pull/74954.diff


2 Files Affected:

- (modified) clang/lib/Basic/Targets/AArch64.cpp (+1) 
- (modified) clang/test/Preprocessor/init-aarch64.c (+1) 


``````````diff
diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
index c31f2e0bee5439..07f86b62d86e1a 100644
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -579,6 +579,7 @@ void AArch64TargetInfo::getTargetDefines(const LangOptions &Opts,
   Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2");
   Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4");
   Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8");
+  Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_16");
 
   // Allow detection of fast FMA support.
   Builder.defineMacro("__FP_FAST_FMA", "1");
diff --git a/clang/test/Preprocessor/init-aarch64.c b/clang/test/Preprocessor/init-aarch64.c
index b0333b3f023890..94c091a69e8444 100644
--- a/clang/test/Preprocessor/init-aarch64.c
+++ b/clang/test/Preprocessor/init-aarch64.c
@@ -118,6 +118,7 @@
 // AARCH64-NEXT: #define __FP_FAST_FMAF 1
 // AARCH64-NEXT: #define __GCC_ASM_FLAG_OUTPUTS__ 1
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
+// AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 1
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
 // AARCH64-NEXT: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1

``````````

</details>


https://github.com/llvm/llvm-project/pull/74954