[PATCH] D38862: Add must alias info to ModRefInfo.

[Alina Sbirlea via Phabricator via llvm-commits]

asbirlea created this revision.
Herald added a subscriber: sanjoy.

Add an additional bit to ModRefInfo, MRI_Must, to be set for known must aliases.
Conservatively this bit will not be set (equivalent to MayAlias or NoAlias).

Notes:

- MRI_Must is almost entirely set in the AAResults methods, the remaining changes are trying to preserve it.
- Only some small changes to make custom AA passes set MRI_Must (BasicAA).
- GlobalsModRef already declares a bit of the same value as MRI_Must (MayReadAnyGlobal). No changes to shift the value of MayReadAnyGlobal (see AlignedMap). FunctionInfo.getModRef() masks out everything except MRI_ModRef, so correctness is preserved, but the MRI_Must info is not set/used.
- There are cases where the MRI_Must is not set, e.g. 2 calls that only read will return MRI_NoModRef, though they may read from exactly the same location.


https://reviews.llvm.org/D38862

Files:
  include/llvm/Analysis/AliasAnalysis.h
  lib/Analysis/AliasAnalysis.cpp
  lib/Analysis/AliasAnalysisEvaluator.cpp
  lib/Analysis/AliasSetTracker.cpp
  lib/Analysis/BasicAliasAnalysis.cpp
  lib/Analysis/GlobalsModRef.cpp
  lib/Analysis/MemoryDependenceAnalysis.cpp
  lib/Analysis/MemorySSA.cpp
  lib/Transforms/Scalar/DeadStoreElimination.cpp
  lib/Transforms/Scalar/MemCpyOptimizer.cpp

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