[LLVMbugs] [Bug 16402] New: BlockFrequency underflow leads to slow code for 7zip
bugzilla-daemon at llvm.org
bugzilla-daemon at llvm.org
Fri Jun 21 04:13:57 PDT 2013
http://llvm.org/bugs/show_bug.cgi?id=16402
Bug ID: 16402
Summary: BlockFrequency underflow leads to slow code for 7zip
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Global Analyses
Assignee: unassignedbugs at nondot.org
Reporter: benny.kra at gmail.com
CC: atrick at apple.com, llvmbugs at cs.uiuc.edu,
stoklund at 2pi.dk
Classification: Unclassified
In LzmaEnc_CodeOneBlock in LzmaEnc.c from MultiSouce/Benchmarks/7zip the block
frequency analysis returns 0 frequencies for blocks in the inner loop. The
frequency calculation hits 0 at some point and never recovers. This made
r184105, the change that made spill weight depend on BlockFrequencyInfo,
regress 7zip by 10% due to excessive spilling. Simply raising
BlockFrequency::ENTRY_FREQ recovers the regression.
Can we do something about this? Increasing ENTRY_FREQ looks like a band aid to
me, we could hit this again any time.
--
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20130621/65481526/attachment.html>
More information about the llvm-bugs
mailing list