[clang] [llvm] [clang-tools-extra] [X86] Use plain load/store instead of cmpxchg16b for atomics with AVX (PR #74275)

[James Y Knight via cfe-commits]

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@@ -31259,14 +31274,23 @@ static SDValue LowerATOMIC_STORE(SDValue Op, SelectionDAG &DAG,
   if (!IsSeqCst && IsTypeLegal)
     return Op;
 
-  if (VT == MVT::i64 && !IsTypeLegal) {
+  if (!IsTypeLegal && !Subtarget.useSoftFloat() &&
+      !DAG.getMachineFunction().getFunction().hasFnAttribute(
+          Attribute::NoImplicitFloat)) {
+    SDValue Chain;
+    // For illegal i128 atomic_store, when AVX is enabled, we can simply emit a
+    // vector store.
+    if (VT == MVT::i128) {
+      if (Subtarget.is64Bit() && Subtarget.hasAVX()) {
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jyknight wrote:

Done.

https://github.com/llvm/llvm-project/pull/74275