Linux/Compiler Options: Difference between revisions

'''For Firefox 3 builds, please use --enable-optimize without flags.'''

Our testing has shown that different parts of Mozilla run faster at different optimization levels.  For example, cairo, pixman and sqlite are compiled at -O2 because they are fastest at that level while the JS engine is fastest at -Os. [https://bugzilla.mozilla.org/show_bug.cgi?id=409803#c9]  Don't use --enable-optimize as a place to pass in random compile flags.  That's a global setting that sets optimization levels [http://lxr.mozilla.org/seamonkey/search?string=MODULE_OPTIMIZE_FLAGS throughout the source tree] and is different depending on the module being compiled.

If you still need to pass in other non-optimization flags to the compile, please use CFLAGS and CXXFLAGS instead of passing them to --enable-optimize.

 

The default optimization level on the 1.8 branch (a.k.a Firefox 2) is -O3 which is too aggressive and trades off a lot of space for not much speed.  So you probably want to use --enable-optimize="..." for this release.

 

If you're using gcc 4.1.x you should use -O2 to make things go as fast as possible.  This will result in about a 2MB code size hit.  If you want to avoid that code size hit you can specify "-Os -finline-limit=100" which gives back most of the performance without too much code size growth.  See the notes below.

 

For gcc 4.3.x you can use -O2 for your builds.  The size hit is smaller because of visibility changes in that release of the compiler.