[PATCH] D41576: [SCEV] Be careful with nuw/nsw in InsertBinop

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: sanjoy, mkazantsev, sebpop, jbhateja.

InsertBinop tries to find an appropriate instruction instead of
creating a new instruction. When it check whether instruction is
the same as we need to create it ignores nuw/nsw flags.

It leads to invalid behavior when poison instruction can be used
when it was not expected. Specifically, for example Expander
expands the SCEV built for instruction
%a = add i32 %v, 1
It is possible that InsertBinop can find an instruction
% b = add nuw nsw i32 %v, 1
and will use it instead of version w/o nuw nsw.
It is incorrect.

The patch conservatively ignores all instructions with any of
wrap flags installed.


https://reviews.llvm.org/D41576

Files:
  lib/Analysis/ScalarEvolutionExpander.cpp
  unittests/Analysis/ScalarEvolutionTest.cpp

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