[llvm] AMDGPU: Fix mfma scale source legalization (PR #117238)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

Code inside assert changes the variable instead of the comparison.

Change-Id: I6054f152b551af80499f8a4597ac462f7bb0d383

---
Full diff: https://github.com/llvm/llvm-project/pull/117238.diff


1 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/SIISelLowering.cpp (+2-3) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 1406938592b2cb..e520dfff1016b2 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -15462,9 +15462,8 @@ void SITargetLowering::AdjustInstrPostInstrSelection(MachineInstr &MI,
         int Src0Idx = AMDGPU::getNamedOperandIdx(MI.getOpcode(),
                                                  AMDGPU::OpName::scale_src0);
         if (Src0Idx != -1) {
-          int Src1Idx = Src0Idx + 2;
-          assert(Src1Idx = AMDGPU::getNamedOperandIdx(
-                     MI.getOpcode(), AMDGPU::OpName::scale_src1));
+          int Src1Idx = AMDGPU::getNamedOperandIdx(MI.getOpcode(),
+                                                   AMDGPU::OpName::scale_src1);
           if (TII->usesConstantBus(MRI, MI, Src0Idx) &&
               TII->usesConstantBus(MRI, MI, Src1Idx))
             TII->legalizeOpWithMove(MI, Src1Idx);

``````````

</details>


https://github.com/llvm/llvm-project/pull/117238