[all-commits] [llvm/llvm-project] 106476: [SDAG] Make Select-with-Identity-Fold More Flexibl...

[Marius Kamp via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 10647685ca3cad0107a2f754b21a078405d30359
      https://github.com/llvm/llvm-project/commit/10647685ca3cad0107a2f754b21a078405d30359
  Author: Marius Kamp <msk at posteo.org>
  Date:   2025-05-29 (Thu, 29 May 2025)

  Changed paths:
    M llvm/include/llvm/CodeGen/TargetLowering.h
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.h
    M llvm/lib/Target/ARM/ARMISelLowering.cpp
    M llvm/lib/Target/ARM/ARMISelLowering.h
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/lib/Target/RISCV/RISCVISelLowering.h
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/lib/Target/X86/X86ISelLowering.h

  Log Message:
  -----------
  [SDAG] Make Select-with-Identity-Fold More Flexible; NFC (#136554)

This change adds new parameters to the method
`shouldFoldSelectWithIdentityConstant()`. The method now takes the
opcode of the select node and the non-identity operand of the select
node. To gain access to the appropriate arguments, the call of
`shouldFoldSelectWithIdentityConstant()` is moved after all other checks
have been performed. Moreover, this change adjusts the precondition of
the fold so that it would work for `SELECT` nodes in addition to
`VSELECT` nodes.
    
No functional change is intended because all implementations of
`shouldFoldSelectWithIdentityConstant()` are adjusted such that they
restrict the fold to a `VSELECT` node; the same restriction as before.
    
The rationale of this change is to make more fine grained decisions
possible when to revert the InstCombine canonicalization of
`(select c (binop x y) y)` to `(binop (select c x idc) y)` in the
backends.



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