[llvm] [DAGCombiner] Move handling of atomic loads from SystemZ to DAGCombiner (NFC). (PR #86484)

[Jonas Paulsson via llvm-commits]

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@@ -1454,6 +1454,28 @@ class TargetLoweringBase {
            getLoadExtAction(ExtType, ValVT, MemVT) == Custom;
   }
 
+  /// Same as getLoadExtAction, but for atomic loads.
+  LegalizeAction getAtomicLoadExtAction(unsigned ExtType, EVT ValVT,
+                                        EVT MemVT) const {
+    if (ValVT.isExtended() || MemVT.isExtended()) return Expand;
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JonPsson1 wrote:

This is copied from getLoadExtAction() a few lines up in the file, so maybe do the same..? (Or reformat both, I guess)

https://github.com/llvm/llvm-project/pull/86484