[LLVMbugs] [Bug 14587] New: Building chrome with libc++ takes 22% (7 minutes) longer than building it with libstdc++

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14587

             Bug #: 14587
           Summary: Building chrome with libc++ takes 22% (7 minutes)
                    longer than building it with libstdc++
           Product: libc++
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: All Bugs
        AssignedTo: hhinnant at apple.com
        ReportedBy: nicolasweber at gmx.de
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 9685
  --> http://llvm.org/bugs/attachment.cgi?id=9685
libstdc++ build log

I tried building chrome with libc++ (since we need to ship on 10.6, with a
libc++ set to "all symbols hidden", and statically linked --
https://codereview.chromium.org/11468030/ see . This is research only for now.)

Doing a full build of the 'chrome' target consistently takes longer with libc++
than with libstdc++ (with clang r168474). Building with libc++ takes around 38
minutes, building with libc++ takes around 31 minutes. (I built several times
with both configurations, and the numbers varied by 50s. I interleaved the
builds, so it's unlikely that this is explainable by some big background job
taking up a huge amount of cpu).


I'm attaching the .ninja_log file for both builds. The format is "start
timestamp in ms, end timestamp in ms, 0, output path, hash". With that file, it
should be possible to find out for which files the difference is biggest.

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