[compiler-rt] [tsan][go] use __builtin_memcpy for 128-bit Go atomic args buffer access (PR #213123)

[Vitaly Buka via llvm-commits]

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@@ -931,9 +931,13 @@ void __tsan_go_atomic64_load(ThreadState *thr, uptr cpc, uptr pc, u8 *a) {
 }
 
 #  if __TSAN_HAS_INT128
+// Go's buffer is 8-byte aligned; ALIGNED(8) relaxes the store alignment.
+ALIGNED(8) typedef a128 a128_u64;
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vitalybuka wrote:

`using a128_u64 ALIGNED(8) = a128;`

https://github.com/llvm/llvm-project/pull/213123