[PATCH] D46380: [InstCombine] Extending InstructionSimplify to check OverflowingBinaryOperators and PossiblyExactOperators safety

[Omer Paparo Bivas via Phabricator via llvm-commits]

opaparo created this revision.
opaparo added reviewers: spatel, craig.topper, AndreiGrischenko, zvi, sanjoy.

As of today, InstCombine does not transform patterns that include a OverflowingBinaryOperator or a PossiblyExactOperator, as a transformation may result in a different behavior in the case that that operand loses bits. However, in many cases these operators can be proven to not violate their restrictions and not lose bits, and so we are missing safe transformation opportunities.
These patch introduces safety checks for the OverflowingBinaryOperators 'add', 'sub', 'mul' and 'shl', and for the PossiblyExactOperators 'ashr' and 'lshr', enabling new kinds of transformations.


Repository:
  rL LLVM

https://reviews.llvm.org/D46380

Files:
  include/llvm/Analysis/ValueTracking.h
  lib/Analysis/InstructionSimplify.cpp
  lib/Analysis/ValueTracking.cpp
  lib/Transforms/InstCombine/InstCombineAddSub.cpp
  lib/Transforms/InstCombine/InstCombineInternal.h
  lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  test/Transforms/InstCombine/select-bitext-bitwise-ops.ll
  test/Transforms/InstCombine/select-obo-peo-ops.ll

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