[llvm] [AMDGPU] Account for existing SDWA selections (PR #123221)

[Frederik Harwath via llvm-commits]

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@@ -187,6 +196,8 @@ class SDWADstPreserveOperand : public SDWADstOperand {
         Preserve(PreserveOp) {}
 
   bool convertToSDWA(MachineInstr &MI, const SIInstrInfo *TII) override;
+  bool canCombineSelections(const MachineInstr &MI,
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frederik-h wrote:

It was strictly necessary as long as the check was outside of `potentialToConvert`; see also https://github.com/llvm/llvm-project/pull/123221#discussion_r1967148059.

https://github.com/llvm/llvm-project/pull/123221