[all-commits] [llvm/llvm-project] 54cb40: [X86][ISel][FMA] Get a handle on operand nodes whe...

[Vineet Kumar via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 54cb4059da2751758b3ab6dc5630e40b228bcda5
      https://github.com/llvm/llvm-project/commit/54cb4059da2751758b3ab6dc5630e40b228bcda5
  Author: Vineet Kumar <173554+vntkmr at users.noreply.github.com>
  Date:   2025-03-17 (Mon, 17 Mar 2025)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    A llvm/test/CodeGen/X86/combine-fma-negate.ll

  Log Message:
  -----------
  [X86][ISel][FMA] Get a handle on operand nodes when negating FMA (#130176)

When negating an FMA opcode, a new node created for a negated FMA
operand may be deleted while recursively negating another FMA operand.
This causes the following assertion to fail:
```
llc: /root/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:7686: llvm::SDValue llvm::SelectionDAG::getNode(unsigned int, const llvm::SDLoc&, llvm::EVT, llvm::SDValue, llvm::SDValue, llvm::SDValue, llvm::SDNodeFlags): Assertion `N1.getOpcode() != ISD::DELETED_NODE && N2.getOpcode() != ISD::DELETED_NODE && N3.getOpcode() != ISD::DELETED_NODE && "Operand is DELETED_NODE!"' failed.
```
This patch adds a temporary handle on the new negated nodes to prevent
them from being deleted.
For eg. see https://godbolt.org/z/Tq4PvnKM4 .

Co-authored-by: Vineet Kumar <vineetk at hpe.com>



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