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

[Jeffrey Byrnes via llvm-commits]

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@@ -158,15 +166,16 @@ class SDWADstOperand : public SDWAOperand {
   DstUnused DstUn;
 
 public:
-
   SDWADstOperand(MachineOperand *TargetOp, MachineOperand *ReplacedOp,
                  SdwaSel DstSel_ = DWORD, DstUnused DstUn_ = UNUSED_PAD)
-    : SDWAOperand(TargetOp, ReplacedOp), DstSel(DstSel_), DstUn(DstUn_) {}
+      : SDWAOperand(TargetOp, ReplacedOp), DstSel(DstSel_), DstUn(DstUn_) {}
 
   MachineInstr *potentialToConvert(const SIInstrInfo *TII,
                                    const GCNSubtarget &ST,
                                    SDWAOperandsMap *PotentialMatches = nullptr) override;
   bool convertToSDWA(MachineInstr &MI, const SIInstrInfo *TII) override;
+  bool canCombineSelections(const MachineInstr &MI,
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jrbyrnes wrote:

Should we also check this in `SDWADstOperand::potentialToConvert` ? 

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