[all-commits] [llvm/llvm-project] 6646b6: [LAA] Rework and rename stripGetElementPtr (#125315)

[Ramkumar Ramachandra via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6646b65082e8bc5f485c744a9c15344011c6aede
      https://github.com/llvm/llvm-project/commit/6646b65082e8bc5f485c744a9c15344011c6aede
  Author: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
  Date:   2025-02-18 (Tue, 18 Feb 2025)

  Changed paths:
    M llvm/lib/Analysis/LoopAccessAnalysis.cpp
    M llvm/test/Analysis/LoopAccessAnalysis/symbolic-stride.ll

  Log Message:
  -----------
  [LAA] Rework and rename stripGetElementPtr (#125315)

The stripGetElementPtr function is mysteriously named, and calls into
another mysterious getGEPInductionOperand which does something
complicated with GEP indices. The real purpose of the badly-named
stripGetElementPtr function is to get a loop-variant GEP index, if there
is one. The getGEPInductionOperand is totally redundant, as stripping
off zeros from the end of GEP indices has no effect on computing the
loop-variant GEP index, as constant zeros are always loop-invariant.
Moreover, the GEP induction operand is simply the first non-zero index
from the end, which stripGetElementPtr returns when it finds that any of
the GEP indices are loop-variant: this is a completely unrelated value
to the GEP index that is loop-variant. The implicit assumption here is
that there is only ever one loop-variant index, and it is the first
non-zero one from the end.

The logic is unnecessarily complicated for what stripGetElementPtr wants
to achieve, and the header comments are confusing as well. Strip
getGEPInductionOperand, rework and rename stripGetElementPtr.



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