[all-commits] [llvm/llvm-project] 402b98: AMDGPU: Fix assert when multi operands to update a...

[macurtis-amd via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 402b989693a0d5d17be6bf996bce52cf3ca73886
      https://github.com/llvm/llvm-project/commit/402b989693a0d5d17be6bf996bce52cf3ca73886
  Author: macurtis-amd <macurtis at amd.com>
  Date:   2025-07-16 (Wed, 16 Jul 2025)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
    A llvm/test/CodeGen/AMDGPU/bug-multi-operands-to-update-after-fold.mir

  Log Message:
  -----------
  AMDGPU: Fix assert when multi operands to update after folding imm (#148205)

In the original motivating test case,
[FoldList](https://github.com/llvm/llvm-project/blob/d8a2141ff98ee35cd1886f536ccc3548b012820b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp#L1764)
had entries:
```
  #0: UseMI: %224:sreg_32 = S_OR_B32 %219.sub0:sreg_64, %219.sub1:sreg_64, implicit-def dead $scc
      UseOpNo: 1

  #1: UseMI: %224:sreg_32 = S_OR_B32 %219.sub0:sreg_64, %219.sub1:sreg_64, implicit-def dead $scc
      UseOpNo: 2
```
After calling
[updateOperand(#0)](https://github.com/llvm/llvm-project/blob/d8a2141ff98ee35cd1886f536ccc3548b012820b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp#L1773),
[tryConstantFoldOp(#0.UseMI)](https://github.com/llvm/llvm-project/blob/d8a2141ff98ee35cd1886f536ccc3548b012820b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp#L1786)
removed operand 1, and entry #​1.UseOpNo was no longer valid,
resulting in an
[assert](https://github.com/llvm/llvm-project/blob/4a35214bddbb67f9597a500d48ab8c4fb25af150/llvm/include/llvm/ADT/ArrayRef.h#L452).

This change defers constant folding until all operands have been updated
so that UseOpNo values remain stable.



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