[Mesa-dev] [PATCH] configure.ac: Save user {C, CXX}FLAGS and append them at end.

[Johannes Obermayr]

Am Samstag, 22. Dezember 2012, 16:34:48 schrieben Sie:
> On Sat, Dec 22, 2012 at 10:47 AM, Johannes Obermayr
> <johannesobermayr at gmx.de> wrote:
> > Am Samstag, 22. Dezember 2012, 09:21:33 schrieb Matt Turner:
> >> On Sat, Dec 22, 2012 at 9:16 AM, Johannes Obermayr
> >> <johannesobermayr at gmx.de> wrote:
> >> > This way the user has the privilege of last decision and so the option to build an optimized debug build again.
> >> > ---
> >>
> >> You can just do CFLAGS="-g -O2" ./configure can't you?
> >
> > Nope.
> >
> > CXXFLAGS='-fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g' CFLAGS='-fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g' ./autogen.sh --host=x86_64-suse-linux-gnu --build=x86_64-suse-linux-gnu --program-prefix= --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64 --libexecdir=/usr/lib --localstatedir=/var --sharedstatedir=/usr/com --mandir=/usr/share/man --infodir=/usr/share/info --disable-dependency-tracking --enable-xvmc --enable-vdpau --enable-texture-float --enable-debug --with-dri-drivers=i915,i965,nouveau,r200,radeon,swrast --with-gallium-drivers=i915,nouveau,r300,r600,svga,swrast --enable-dri --enable-glx --enable-osmesa --enable-gles1 --enable-gles2 --enable-openvg --enable-shared-glapi --enable-shared-gallium --enable-gbm --enable-xa --ena
> >  ble-gallium-egl --enable-gallium-llvm --enable-gallium-gbm --enable-opencl --enable-r600-llvm-compiler --enable-gallium-g3dvl --enable-glx-tls
> >
> > Resulting Makefile:
> > before:
> > CFLAGS = -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -Wall -std=c99 -Werror=implicit-function-declaration -Werror=missing-prototypes -fno-strict-aliasing -fno-builtin-memcmp -g -O0
> >
> > after:
> > CFLAGS =  -Wall -std=c99 -Werror=implicit-function-declaration -Werror=missing-prototypes -fno-strict-aliasing -fno-builtin-memcmp -g -O0 -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g
> >
> > You see configure CFLAGS and initial CFLAGS are vice versa.
> 
> The real fix here is not to have configure.ac touch CFLAGS at all like
> any reasonable autotools project. That was an unfortunate shortcut
> during the initial work. That would be a lot more effort, though.

Initial work after ~ 5 years?
http://cgit.freedesktop.org/mesa/mesa/commit/?id=122345876479cf5cf553e38162ab105658614ab7

Btw:
http://cgit.freedesktop.org/mesa/mesa/commit/?id=ff2efdf5997d20b41f7a82b77118366e6fbd23bc
http://cgit.freedesktop.org/mesa/mesa/commit/?id=33ae29c93b8f70a86dcedc495dd658a5d5679db3

This patch covers the motivation for commit 33ae29c.

> 
> However, the typical convention is that the user's CFLAGS come first
> (see any automake COMPILE or LTCOMPILE definition), mostly so that any
> user specified -I paths take precedence. That's unfortunate when -O
> options to gcc are last one wins, but that's how things have typically
> been. I would make this change very cautiously.
> 
> --
> Dan

And here is the real reason for my request:

/usr/lib64/mesa-demos/egl/opengl/xeglgears

AMD Fusion	 (fps)			Nvidia ION (fps)
-O0	-O2			-O0	-O2
562,7	750,778	0,33		641,851	921,464	0,44
701,756	662,877	-0,06		693,752	1000,196	0,44
571,566	665,052	0,16		692,196	936,147	0,35
542,715	664,658	0,22		693,733	995,499	0,43
542,935	664,78	0,22		692,702	992,634	0,43
542,574	665,398	0,23		692,835	998,665	0,44
542,945	663,087	0,22		691,353	998,319	0,44
541,732	664,253	0,23		656,32	995,91	0,52
543,392	665,078	0,22		691,084	994,037	0,44
542,901	663,406	0,22		693,464	996,858	0,44
5635,216	6729,367	0,19		6839,29	9829,729	0,44 (sum)

-> Performance + 19 % on AMD Fusion, + 44 % on Nvidia ION on debug build with -O2. :-)

Usual users should build Mesa with default FLAGS. Advanced users should be able to build it with their own FLAGS without modifying source.