Serguei Katkov 9c3564018d [GVN PRE] Patch the source for Phi node in PRE
We must patch all existing incoming values of Phi node,
otherwise it is possible that we can see poison
where program does not expect to see it.

This is the similar what GVN does.

The added test test/Transforms/GVN/PRE/pre-jt-add.ll shows an
example of wrong optimization done by jump threading due to
GVN PRE did not patch existing incoming value.

Reviewers: mkazantsev, wmi, dberlin, davide
Reviewed By: dberlin
Subscribers: efriedma, llvm-commits
Differential Revision: https://reviews.llvm.org/D39637


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317768 91177308-0d34-0410-b5e6-96231b3b80d8
2017-11-09 06:02:18 +00:00
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2017-10-19 01:32:18 +00:00
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