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Bug 47769 - ScalarEvolution can introduce branch on poison
Summary: ScalarEvolution can introduce branch on poison
Status: NEW
Alias: None
Product: libraries
Classification: Unclassified
Component: Scalar Optimizations (show other bugs)
Version: trunk
Hardware: PC All
: P normal
Assignee: Unassigned LLVM Bugs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-10-08 10:02 PDT by Kevin Jacobus de Vos
Modified: 2020-10-08 10:02 PDT (History)
8 users (show)

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Description Kevin Jacobus de Vos 2020-10-08 10:02:00 PDT 
Test: Transforms/LoopVectorize/pr30654-phiscev-sext-trunc.ll
Function: doit1
Reason: Source more defined than target

Example: https://godbolt.org/z/1nMsMT
LoopVectorize adds the block vector.scevcheck and uses SCEVExpander to generate checks that use %step. If %step is poison it introduces branch on poison.