[PATCH] D138790: [DAG] Attempt to replace a mul nodes with an existing umul_lohi/smul_lohi node (PR59217)

[Simon Pilgrim via Phabricator via llvm-commits]

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As discussed on Issue #59217, under certain circumstances the DAG can generate duplicate MUL and MUL_LOHI nodes, often during MULO legalization.

This patch attempts to replace MUL nodes with additional uses of the LO result from the MUL_LOHI node.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138790

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/AMDGPU/llvm.mulo.ll
  llvm/test/CodeGen/X86/combine-mul.ll
  llvm/test/CodeGen/X86/muloti.ll
  llvm/test/CodeGen/X86/smul-with-overflow.ll
  llvm/test/CodeGen/X86/smul_fix_sat.ll
  llvm/test/CodeGen/X86/smulo-128-legalisation-lowering.ll
  llvm/test/CodeGen/X86/vec_smulo.ll
  llvm/test/CodeGen/X86/xmulo.ll

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