[all-commits] [llvm/llvm-project] b8917a: [LICM] Reassociate GEPs to allow hoisting

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: b8917ac62ad49a0ce6de026c086599fc5fa35566
      https://github.com/llvm/llvm-project/commit/b8917ac62ad49a0ce6de026c086599fc5fa35566
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2023-04-11 (Tue, 11 Apr 2023)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LICM.cpp
    M llvm/test/CodeGen/PowerPC/no-ctr-loop-if-exit-in-nested-loop.ll
    M llvm/test/Transforms/LICM/gep-reassociate.ll

  Log Message:
  -----------
  [LICM] Reassociate GEPs to allow hoisting

Reassociate gep (gep ptr, idx1), idx2 to gep (gep ptr, idx2), idx1
if this would make the inner GEP loop invariant and thus hoistable.

This is intended to replace an InstCombine fold that does this (in
https://github.com/llvm/llvm-project/blob/04f61fb73dc6a994ab267d431f2fdaedc67430ff/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp#L2006).
The problem with the InstCombine fold is that LoopInfo is an optional
dependency, so it is not performed reliably.

Differential Revision: https://reviews.llvm.org/D146813