[PATCH] D34702: [DependenceAnalysis] Make sure base objects are the same when comparing GEPs

[Brendon Cahoon via Phabricator via llvm-commits]

bcahoon created this revision.

The dependence analysis was returning incorrect information when using the GEPs to compute the dependence. The analysis uses the GEP indices to perform the check under certain conditions. It incorrectly does this if the base objects are aliases, but are actually pointing to different locations in an array. Because the SCEVs for the GEPs indices were the same, DA returns a distance of 0.

      

This patch adds another check for the base objects. If the SCEVs for the base pointers are compared, using getMinusSCEV() and the value is not 0, the analysis should fall back on the path that uses the whole SCEV for the dependence check. Not just the GEP indices.

Fixes bug 33567.


https://reviews.llvm.org/D34702

Files:
  lib/Analysis/DependenceAnalysis.cpp
  test/Analysis/DependenceAnalysis/BasePtrBug.ll
  test/Analysis/DependenceAnalysis/BasePtrBug1.ll

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