[PATCH] D118024: [sanitizer_common] Use atomic builtin in sanitizer_atomic_clang.h

[Rainer Orth via Phabricator via llvm-commits]

ro updated this revision to Diff 403940.
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Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118024/new/

https://reviews.llvm.org/D118024

Files:
  compiler-rt/lib/sanitizer_common/sanitizer_atomic_clang.h


Index: compiler-rt/lib/sanitizer_common/sanitizer_atomic_clang.h
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_atomic_clang.h
+++ compiler-rt/lib/sanitizer_common/sanitizer_atomic_clang.h
@@ -74,13 +74,12 @@
 inline bool atomic_compare_exchange_strong(volatile T *a, typename T::Type *cmp,
                                            typename T::Type xchg,
                                            memory_order mo) {
-  typedef typename T::Type Type;
-  Type cmpv = *cmp;
-  Type prev;
-  prev = __sync_val_compare_and_swap(&a->val_dont_use, cmpv, xchg);
-  if (prev == cmpv) return true;
-  *cmp = prev;
-  return false;
+  // Transitioned from __sync_val_compare_and_swap to support targets like
+  // SPARC V8 that cannot inline atomic cmpxchg.  __atomic_compare_exchange
+  // can then be resolved from libatomic.  __ATOMIC_SEQ_CST is used to best
+  // match the __sync builtin memory order.
+  return __atomic_compare_exchange(&a->val_dont_use, cmp, &xchg, false,
+                                   __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
 }
 
 template<typename T>


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