[llvm-bugs] [Bug 34101] New: deriche: performance difference with -polly-position=before-vectorizer

via llvm-bugs llvm-bugs at lists.llvm.org
Mon Aug 7 05:21:27 PDT 2017


            Bug ID: 34101
           Summary: deriche: performance difference with
           Product: Polly
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Optimizer
          Assignee: polly-dev at googlegroups.com
          Reporter: simbuerg at fim.uni-passau.de
                CC: llvm-bugs at lists.llvm.org

Created attachment 18921
  --> https://bugs.llvm.org/attachment.cgi?id=18921&action=edit
Preprocessed sources with reduced deriche kernel

Hi, using the (somewhat reduced) version of polybench's deriche kernel I get
the following two (weird) results when I compare Polly before the vectorizer to
its default position:

clang -mllvm -polly -mllvm -polly-position=before-vectorizer -O3 -I utilities
-DPOLYBENCH_USE_RESTRICT utilities/polybench.c deriche.dir/deriche.c -lm -o

clang -mllvm -polly -O3 -I utilities -I deriche -DPOLYBENCH_USE_C99_PROTO
deriche.dir/deriche.c -lm -o ./deriche.default.bin

master* ⇣ simbuerg at ligeti 6s
❯ time ./deriche.vect.bin
./deriche.vect.bin  23.34s user 0.02s system 99% cpu 23.357 total

master* ⇣ simbuerg at ligeti 23s
❯ time ./deriche.default.bin      ./deriche.default.bin  0.13s user 0.00s
system 96% cpu 0.141 total

Expected result: The produced code should not get slower that without polly

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