[LLVMbugs] [Bug 14651] New: CLANG Compilation 4x Slower Than GCC

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Dec 19 08:50:22 PST 2012


             Bug #: 14651
           Summary: CLANG Compilation 4x Slower Than GCC
           Product: clang
           Version: 3.1
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: Driver
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: ed4online at me.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 9740
  --> http://llvm.org/bugs/attachment.cgi?id=9740
pan.* sources

Compiling 500k of auto-generated source code is approximately 4x slower with
Clang compared to GCC.

ebg at taiyo(13)$ time /usr/local/gcc/bin/gcc -DHC4 -DSAFETY -DNOREDUCE -DNFAIR=3
-O2  -o files pan.c

real    0m41.708s
user    0m39.156s
sys    0m1.375s
ebg at taiyo(14)$ time clang -DHC4 -DSAFETY -DNOREDUCE -DNFAIR=3 -O2  -o files

real    3m49.014s
user    3m41.081s
sys    0m5.819s

ebg at taiyo(56)$ clang -v
Apple clang version 4.0 (tags/Apple/clang-421.0.60) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix

ebg at taiyo(57)$ /usr/local/gcc/bin/gcc -v
Using built-in specs.
Target: x86_64-apple-darwin10.7.0
Configured with: ./configure --prefix=/usr/local/gcc --enable-languages='c c++'
--enable-lto --with-gmp=/usr/local/gcc --with-mpfr=/usr/local/gcc
Thread model: posix
gcc version 4.6.0 (GCC) 

See http://pastebin.com/bmPmBiQJ for 'clang -ftime-report ...'

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