Bug 4706

Summary:	Compile for SSE by default
Product:	pixman	Reporter:	Steve Chaplin <d74n5pohf9>
Component:	pixman	Assignee:	Billy Biggs <billy.biggs>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	critical
Priority:	high	CC:	cworth, otaylor
Version:	0.1.3
Hardware:	x86 (IA32)
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	patch to allow Athlon-XP use SSE

Description Steve Chaplin 2005-10-07 07:46:42 UTC

cairo/pixman/fbmmx.c has lines:
#if defined(__amd64__) || defined(__x86_64__)
#define USE_SSE
#endif

which excludes the Athlon-XP (which supports SSE) from running the SSE code.
(It looks like its excluding the Pentium 3 and Pentium 4 which also
support SSE)

Attached patch allows the Athlon-XP to run the SSE code.
Tested on my system with the imagepattern gtk snippet - the SSE version
of expand_alpha is called and works OK.

It seems odd having MMX selected at run-time and then selecting
SSE at compile-time. I think run-time detection for SSE may be a better
solution.

Comment 1 Steve Chaplin 2005-10-07 07:48:21 UTC

Created attachment 3508 [details] [review]
patch to allow Athlon-XP use SSE

Comment 2 Billy Biggs 2005-10-07 07:57:23 UTC

The patch isn't useful since we need to do runtime CPU detection for x86
systems. Fixing this is a little awkard since the code uses the gcc intrinsics,
so it must be compiled twice, once with -msse and -DUSE_SSE defined, and again
without, using some preprocessor macros to change the function names.

Comment 3 Billy Biggs 2005-10-10 11:19:35 UTC

Or, we can just only compile for SSE, which is also a reasonable suggestion.
Owen things we should first see how much faster the SSE code is from the
MMX code on certain processors.

Comment 4 Søren Sandmann Pedersen 2007-06-20 09:36:18 UTC

At this point it may be best to just compile for SSE exclusively. The set of MMX-but-not-SSE capable CPU's is fairly small.

They do exist though, and the OLPC laptop is an example, so we should provide a configure time option to compile for MMX.

Comment 5 Søren Sandmann Pedersen 2007-06-20 09:38:37 UTC

Closed by mistake

Comment 6 Eugene St Leger 2007-09-20 05:42:31 UTC

I appear to have run in to this bug (I have an old AMD Duron), as detailed in another bug report:
https://bugs.freedesktop.org/show_bug.cgi?id=12398#c6

The debian bug report mentions a fix:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=442829#59

The fix seems to be a workaround.  They seem to have removed the -msse CFLAG, as can be seen here:
http://ftp.debian.org/debian/pool/main/p/pixman/pixman_0.9.5-2.diff.gz

My impression is that it is desired that MMX and SSE should be supported *separately*.  For Gentoo users, it is obviously desirable that libpixman (AKA x11-libs/pixman-0.9.5) should respect the -mmmx and -msse CFLAGS.  I hacked the build system so that I could build a working xserver.  Properly fixing the makefiles is beyond me though.  I have filed a Gentoo bug:
http://bugs.gentoo.org/show_bug.cgi?id=193138

Comment 7 Søren Sandmann Pedersen 2008-10-31 11:43:31 UTC

This bug is obsolete since we don't use the MMX extensions at all anymore.

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