https://llvm.org/bugs/show_bug.cgi?id=26376
Bug ID: 26376
Summary: SROA may create redundant PHI nodes
Product: new-bugs
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 15755
--> https://llvm.org/bugs/attachment.cgi?id=15755&action=edit
test case
I've come across a situation where SROA will create redundant PHI nodes while
promoting an alloca. The old SSAUpdater (optional prior to r246028) was able
to detect the redundancy in this case and avoid it. The PromoteRegToMem class
does not detect the redundancy.
I have seen a case (on 32-bit x86) where this led to an extra select and
resulted in a measurable performance degradation.
The attached test case demonstrates the problem.
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