[llvm] [SystemZ] Don't lower float/double ATOMIC_[LOAD|STORE] to [LOAD|STORE] (PR #75879)

[Matt Arsenault via llvm-commits]

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@@ -338,6 +338,19 @@ SDValue DAGTypeLegalizer::PromoteIntRes_Atomic0(AtomicSDNode *N) {
                               N->getMemoryVT(), ResVT,
                               N->getChain(), N->getBasePtr(),
                               N->getMemOperand());
+  if (N->getOpcode() == ISD::ATOMIC_LOAD) {
+    ISD::LoadExtType ETy = cast<AtomicSDNode>(N)->getExtensionType();
+    if (ETy == ISD::NON_EXTLOAD) {
+      if (TLI.getExtendForAtomicOps() == ISD::SIGN_EXTEND)
+        ETy = ISD::SEXTLOAD;
+      else if (TLI.getExtendForAtomicOps() == ISD::ZERO_EXTEND)
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arsenm wrote:

switch over TLI.getExtendForAtomicOps() (terrible hook btw, one of the plusses of globalisel having G_SEXTLOAD/G_ZEXTLOAD + atomic MMO)

https://github.com/llvm/llvm-project/pull/75879