https://llvm.org/bugs/show_bug.cgi?id=26863
Bug ID: 26863
Summary: InstructionSimplify broadens undef when simplifying
from
Product: libraries
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Global Analyses
Assignee: unassignedb...@nondot.org
Reporter: dav...@cs.rutgers.edu
CC: llvm-bugs@lists.llvm.org,
santosh.nagaraka...@gmail.com
Classification: Unclassified
These optimizations in SimplifyFRemInst, from
lib/Analysis/InstructionSimplify.cpp, potentially introduce new behavior.
// undef % X -> undef (the undef could be a snan).
if (match(Op0, m_Undef()))
return Op0;
// X % undef -> undef
if (match(Op1, m_Undef()))
return Op1;
In the first optimization, undef % X must either result in NaN or a value less
than X.
In the second optimization, X % undef will usually result in NaN or a value
less than X when X is normal.
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