https://llvm.org/bugs/show_bug.cgi?id=25824
Bug ID: 25824
Summary: incorrect saving/restoring points in shrink-wrap
Product: tools
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: llc
Assignee: unassignedb...@nondot.org
Reporter: weimi...@codeaurora.org
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Given a loop, like
HeadBB
/ \
/ \
/ \
ExitingPath\
\
someBB
/ \
/ \
(BB1)Def of CSR \
\
(BB2) Use of CSR
Since HeadBB dominates both BB1 and BB2, and HeadBB post-doms BB1 and BB2,
eventually, it returning HeadBB as saving and restoring point. As a result,
Epilog/Prolog Inserter inserts a pair of push/pop in HeadBB, which in
incorrect.
Domination only guarantees the def in dominator will reach it's descendants,
but it doesn't guarantee the value in HeadBB is before the change made in BB1.
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