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

[Frederik Harwath 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);
+
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frederik-h wrote:

Perhaps add a comment explaining why it is necessary to perform this check here (as in the PR description: "It is not safe to use isOperandLegal on an instruction that does not have a complete set of operands. ...")?

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