[all-commits] [llvm/llvm-project] 4d59ff: [InstCombine] Simplify separate_storage assumptions

[David Goldblatt via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4d59ffb0d19a40c974ce930e8e9336d3df4d2dd3
      https://github.com/llvm/llvm-project/commit/4d59ffb0d19a40c974ce930e8e9336d3df4d2dd3
  Author: David Goldblatt <davidgoldblatt at fb.com>
  Date:   2023-03-03 (Fri, 03 Mar 2023)

  Changed paths:
    M llvm/lib/Analysis/BasicAliasAnalysis.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
    A llvm/test/Transforms/InstCombine/assume-separate_storage.ll

  Log Message:
  -----------
  [InstCombine] Simplify separate_storage assumptions

Before this change, we call getUnderlyingObject on each separate_storage
operand on every alias() call (potentially requiring lots of pointer
chasing). Instead, we rewrite the assumptions in instcombine to do this
pointer-chasing once.

We still leave the getUnderlyingObject calls in alias(), just expecting
them to be no-ops much of the time. This is relatively fast (just a
couple dyn_casts with no pointer chasing) and avoids making alias
analysis results depend on whether or not instcombine has been run.

Differential Revision: https://reviews.llvm.org/D144933