[all-commits] [llvm/llvm-project] 30eff7: [DAG] Attempt to replace a mul node with an existi...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 30eff7f29f97599a94a40907f5b77244af0eaee1
      https://github.com/llvm/llvm-project/commit/30eff7f29f97599a94a40907f5b77244af0eaee1
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2022-11-29 (Tue, 29 Nov 2022)

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

  Log Message:
  -----------
  [DAG] Attempt to replace a mul node with an existing umul_lohi/smul_lohi node (PR59217)

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

Differential Revision: https://reviews.llvm.org/D138790