Overview
Proper use of compiler options
Don't set a default optimization level for the entire browser build.
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. [1] If you want to use --enable-optimize, don't add extra optimization flags there. That's a global setting that sets optimization levels throughout the source tree. Instead pass non-optimization flags that you care about via CFLAGS and CXXFLAGS during the build.
Compilers
| Compiler + Options |
Notes |
| gcc 4.1.2 (-Os -freorder-blocks -fno-reorder-functions) |
Baseline for testing. Very similar to our reference platform, which uses gcc 4.1.1. Those options above are the default options that we use for compiling.
This compiler version apparently does not inline even trivial functions.[2]
|
| gcc 4.2.1 (-Os -freorder-blocks -fno-reorder-functions -finline-limit=50) |
Note the use of -finline-limit=n. This will force many small functions and helpers to be inlined. (-O2 uses 600 as a value, for example.) On a 32-bit Linux build this results in:
codesize saving of 225kb (2%)
Ts win of 3%
Txul win of 18%
Tp2 win of about 25% (!)
|
| gcc 4.2.1 (-O2 -freorder-blocks -fno-reorder-functions) |
Comparing -O2 vs. -Os -finline-limit=50, not directly against baseline. [3]
Txul is unchanged
Ts improves 3%
Tp2 improves about 4%
however, codesize jumps 2,414kb (19%)
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Distributions
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Name
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GCC Version
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Last Build
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Ubuntu 7.10
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gcc version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)
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2.0.0.11+2nobinonly-0ubuntu0.7.10 (2008-01-07)
|
|
gcc flags
-Wall -W -Wno-unused -Wpointer-arith -Wcast-align -Wno-long-long -pedantic -g -Wall -O2 -pthread -pipe
g++ flags
-fno-rtti -fno-exceptions -Wall -Wconversion -Wpointer-arith -Wcast-align -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor -Wno-long-long -pedantic -g -Wall -O2 -fshort-wchar -pthread -pipe
configure flags
--build=i486-linux-gnu --prefix=/usr '--includedir=${prefix}/include' '--mandir=${prefix}/share/man' '--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var '--libexecdir=${prefix}/lib/firefox' --disable-maintainer-mode --disable-dependency-tracking --srcdir=. --disable-debug --with-default-mozilla-five-home= --with-user-appdir=.mozilla --with-system-png=/usr --with-system-jpeg=/usr --with-system-zlib=/usr --with-system-nspr --with-system-nss --disable-composer --disable-debug --disable-elf-dynstr-gc --disable-gtktest --disable-installer --disable-ldap --disable-mailnews --disable-profilesharing --disable-strip --disable-strip-libs --disable-tests --disable-updater --disable-xprint --enable-application=browser --enable-canvas --enable-default-toolkit=gtk2 --enable-gnomevfs --enable-libthai '--enable-optimize=-pipe\ -w\ -O2\ -fno-strict-aliasing\ -g' --enable-pango --enable-postscript --enable-svg --enable-svg-renderer=cairo --enable-system-cairo --enable-mathml --enable-xft --enable-xinerama --enable-extensions=default --enable-single-profile --enable-system-myspell --with-distribution-id=com.ubuntu --enable-official-branding --enable-system-c
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Fedora 8
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gcc version 4.1.2 20070925 (Red Hat 4.1.2-33)
|
firefox-2.0.0.10-3.fc8
(2008-01-04)
|
|
gcc flags
-Wall -W -Wno-unused -Wpointer-arith -Wcast-align -Wno-long-long -pedantic -pthread -pipe
g++ flags
-fno-rtti -fno-exceptions -Wall -Wconversion -Wpointer-arith -Wcast-align -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor -Wno-long-long -pedantic -fshort-wchar -pthread -pipe
configure flags
--enable-application=browser --prefix=/usr --libdir=/usr/lib --with-system-nspr --with-system-nss --with-system-jpeg --with-system-zlib --with-system-png --with-pthreads --disable-tests --disable-debug --disable-installer '--enable-optimize=-Os -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables' --enable-xinerama --enable-default-toolkit=gtk2 --disable-xprint --disable-strip --enable-pango --enable-system-cairo --enable-svg --enable-canvas --enable-startup-notification --enable-official-branding
|
|
CentOS 5.1
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gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)
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firefox-1.5.0.12-7.el5.centos (2008-01-07)
|
|
gcc flags
-Wall -W -Wno-unused -Wpointer-arith -Wcast-align -Wno-long-long -pedantic -pthread -pipe
g++ flags
-fno-rtti -fno-exceptions -Wall -Wconversion -Wpointer-arith -Wcast-align -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor -Wno-long-long -pedantic -fshort-wchar -pthread -pipe
configure flags
--enable-application=browser --prefix=/usr --libdir=/usr/lib --with-system-nspr --with-system-nss --with-system-jpeg --with-system-zlib --with-system-png --with-pthreads --disable-tests --disable-debug --disable-installer '--enable-optimize=-Os -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables' --enable-xinerama --enable-default-toolkit=gtk2 --disable-xprint --disable-strip --enable-pango --enable-system-cairo --enable-svg --enable-canvas --enable-official-branding
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