https://llvm.org/bugs/show_bug.cgi?id=23527
Bug ID: 23527
Summary: [ScalarEvolution] createNodeForGEP over-optimistic
about preserving nsw
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Global Analyses
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
[Copied from llvmdev@]
I was looking at ScalarEvolution::createNodeForGEP
(http://llvm.org/docs/doxygen/html/ScalarEvolution_8cpp_source.html#l03702),
and noticed that the code that applies nsw flags to the resultant SCEV is
inconsistent with the comment.
While the comment says
03709 // Don't blindly transfer the inbounds flag from the GEP instruction to
the
03710 // Add expression, because the Instruction may be guarded by control
flow
03711 // and the no-overflow bits may not be valid for the expression in any
03712 // context.
03713 SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW :
SCEV::FlagAnyWrap;
the code still transfers nsw to LocalOffset and BaseS+TotalOffset.
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