[webkit-dev] command line JSC vs. JSC in libQtWebKit

Osztrogonac Csaba oszi at inf.u-szeged.hu
Thu Feb 26 01:55:20 PST 2009

Maciej Stachowiak írta:
> On other platforms, we try to build the JavaScriptCore object files with 
> -O3 and strict aliasing enabled, even if the rest of WebKit is not. For 
> example, on Mac, JavaScriptCore.framework builds with "-O3 
> -fstrict-aliasing -fomit-frame-pointer" even though WebCore.framework 
> builds with "-O2 -fno-strict-aliasing". So I suggest fixing this in the 
> libQtWebKit build.

I tried building jsc, libQtWebkit and WebCore with all combination of
these gcc options. Between "-O2 -fno-strict-aliasing" and "-O3" is
irrelevant. (<1%) The different caused by -fPIC option, which is
neccessary if building libQtWebKit shared library.

The solution can be building command line jsc with -fPIC too. It
will cause 12% slowdown, but the performance will be same as jsc
in libQtWebKit. I think it's correct to measure SunSpider test
with such jsc as in libQtWebKit, because several optimizations
have different effect on different jsc's.

Csaba Osztrogonac

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