[llvm-branch-commits] [llvm] AMDGPU: Fix DPP combiner using isOperandLegal on incomplete inst (PR #155595)

[Matt Arsenault via llvm-branch-commits]

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@@ -431,6 +422,19 @@ MachineInstr *GCNDPPCombine::createDPPInst(MachineInstr &OrigMI,
     DPPInst.add(*TII->getNamedOperand(MovMI, AMDGPU::OpName::row_mask));
     DPPInst.add(*TII->getNamedOperand(MovMI, AMDGPU::OpName::bank_mask));
     DPPInst.addImm(CombBCZ ? 1 : 0);
+
+    for (AMDGPU::OpName Op :
+         {AMDGPU::OpName::src0, AMDGPU::OpName::src1, AMDGPU::OpName::src2}) {
+      int OpIdx = AMDGPU::getNamedOperandIdx(DPPOp, Op);
+      if (OpIdx == -1)
+        break;
+
+      if (!TII->isOperandLegal(*DPPInst, OpIdx)) {
+        LLVM_DEBUG(dbgs() << "  failed: src operand is illegal\n");
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arsenm wrote:

Not sure we have a way to get the name of the index from the OpName 

https://github.com/llvm/llvm-project/pull/155595