[LLVMbugs] [Bug 10651] New: File takes 8s to compiled with clang but only 74ms to compile with gcc

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sat Aug 13 04:44:52 PDT 2011


           Summary: File takes 8s to compiled with clang but only 74ms to
                    compile with gcc
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: stark at mit.edu
                CC: llvmbugs at cs.uiuc.edu

The build times for Postgres are still slower with clang than gcc. On my
machine Postgres builds in about 90s with gcc but takes nearly 4 minutes with
clang. There is no longer a single offending file but there are a bunch of
files that seem to take 5-8s with clang even though they don't take
particularly long with gcc. This is true even with -O0.

This is the current worst offender but there are 17 files that take 10 times as
long or more to build with clang as gcc.

These times are after running the two commands repeatedly:

$ time gcc -c syscache-preprocessed.c 

real    0m0.074s
user    0m0.050s
sys     0m0.040s

$ time clang -c syscache-preprocessed.c 

real    0m7.742s
user    0m7.700s
sys     0m0.040s

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