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Bug 26434 - [Polly] -polly-parallel miscompiles two LNT benchmarks
Summary: [Polly] -polly-parallel miscompiles two LNT benchmarks
Status: RESOLVED FIXED
Alias: None
Product: Polly
Classification: Unclassified
Component: Optimizer (show other bugs)
Version: unspecified
Hardware: PC Linux
: P normal
Assignee: Polly Development Mailinglist
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-02-02 05:13 PST by Tobias Grosser
Modified: 2016-02-07 06:50 PST (History)
2 users (show)

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Description Tobias Grosser 2016-02-02 05:13:05 PST 
We see currently two miscompiles in LNT with -polly-parallel:

http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3-polly-parallel-fast/builds/15119
Comment 1 Roman Gareev 2016-02-04 04:11:40 PST 
I’m not able to reproduce them on my target machine. I’ve run the LNT with the following options:

~/mysandbox/bin/lnt runtest nt --sandbox SANDBOX --cc "/home/roman/Documents/polly/build/llvm/bin/clang" --cxx "/home/roman/Documents/polly/build/llvm/bin/clang++"  --cflags=" -lgomp -Xclang -load -Xclang /tmp_home/compiled/llvm/lib/LLVMPolly.so -O3 -mllvm -polly -mllvm -polly-parallel" --test-suite ~/llvm-test-suite

Have I missed something?
Comment 2 Tobias Grosser 2016-02-04 04:15:23 PST 
I had issues reproducing them as well. So no, this does not seem to be an easy/simple to debug issue.
Comment 3 Tobias Grosser 2016-02-07 06:50:02 PST 
This was likely not a miscompile, but rather too many threads running in parallel as we run LNT with -j16 and then allowed each program to create itself threads without limitation (which resulted in one thread per core and process). This issue was resolved by hardcoding the number of parallel threads per process with OMP_NUM_THREADS=2.