http://llvm.org/bugs/show_bug.cgi?id=12526
Bug #: 12526
Summary: Unnecessary register spill (seems easily avoidable)
Product: new-bugs
Version: trunk
Platform: PC
OS/Version: All
Status: NEW
Severity: normal
Priority: P
Component: new bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 8371
--> http://llvm.org/bugs/attachment.cgi?id=8371
bitcode
The attached case shows a very easily avoided register spill. (The source is a
dense matrix multiply routine.) In LBB1_2, %ymm10 is spilled and then reloaded
10 or so instructions later. Across these instructions, %ymm2-5 (at least) are
all dead, so the spill shouldn't be necessary at all. (Unless I'm missing
something!)
Though this is just a single spill, it's a pretty simple repro case, with
surprising behavior. I've seen a number of other cases with quite a bit of
unnecessary spilling with SSE/AVX registers, but the attached is a reasonably
straightforward, so I hope it's useful.
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