| Message ID | 201610022253.17825.cehoyos@ag.or.at |
|---|---|
| State | Rejected |
| Headers | show |
On Sun, Oct 2, 2016 at 10:53 PM, Carl Eugen Hoyos <cehoyos@ag.or.at> wrote: > Hi! > > The functions in libavutil/x86/pixelutils.asm are exported > to the library users if I understand the code correctly. > I suspect it can be expected that the MMX state is reset > after returning. > > Fixes the pixelutils fate test with musl on x86-32. > > Please comment, Carl Eugen > These functions are called in tight loops, and emms is then called in the user-code after the loop. Calling emms inside the DSP function would result in a performance degredation. If a test doesn't call emms after using it, then that should be fixed. And the docs should perhaps be amended to make note of that. Many DSP functions work like that, to allow using them in tight loops without the overhead. - Hendrik
On Sun, Oct 02, 2016 at 10:53:17PM +0200, Carl Eugen Hoyos wrote: > Hi! > > The functions in libavutil/x86/pixelutils.asm are exported > to the library users if I understand the code correctly. > I suspect it can be expected that the MMX state is reset > after returning. > > Fixes the pixelutils fate test with musl on x86-32. > > Please comment, Carl Eugen > pixelutils.asm | 5 +++++ > 1 file changed, 5 insertions(+) > a7b729f55ec6170b1c4b1959a4be7530926368ce 0001-lavu-x86-pixelutils-Call-emms-before-returning.patch > From f16831e6dc0f36c8f290d927bf51142c64fe8afc Mon Sep 17 00:00:00 2001 > From: Carl Eugen Hoyos <cehoyos@ag.or.at> > Date: Sun, 2 Oct 2016 22:45:51 +0200 > Subject: [PATCH] lavu/x86/pixelutils: Call emms before returning. > > The functions are exported and the library user can > expect that the MMX state is reset after returning. > --- > libavutil/x86/pixelutils.asm | 5 +++++ > 1 file changed, 5 insertions(+) I think the performance impact of this on some CPUs is too large to call this at a 8x8 and 16x16 granularity [...]
diff --git a/libavutil/x86/pixelutils.asm b/libavutil/x86/pixelutils.asm index 7af3007..092eb6e 100644 --- a/libavutil/x86/pixelutils.asm +++ b/libavutil/x86/pixelutils.asm @@ -61,6 +61,7 @@ cglobal pixelutils_sad_8x8, 4,4,0, src1, stride1, src2, stride2 paddw m6, m0 movd eax, m6 movzx eax, ax + emms RET ;------------------------------------------------------------------------------- @@ -81,6 +82,7 @@ cglobal pixelutils_sad_8x8, 4,4,0, src1, stride1, src2, stride2 lea src2q, [src2q + 2*stride2q] %endrep movd eax, m2 + emms RET ;------------------------------------------------------------------------------- @@ -101,6 +103,7 @@ cglobal pixelutils_sad_16x16, 4,4,0, src1, stride1, src2, stride2 add src2q, stride2q %endrep movd eax, m2 + emms RET ;------------------------------------------------------------------------------- @@ -131,6 +134,7 @@ cglobal pixelutils_sad_16x16, 4,4,5, src1, stride1, src2, stride2 movhlps m0, m4 paddw m4, m0 movd eax, m4 + emms RET ;------------------------------------------------------------------------------- @@ -158,6 +162,7 @@ cglobal pixelutils_sad_%1_16x16, 4,4,3, src1, stride1, src2, stride2 movhlps m0, m2 paddw m2, m0 movd eax, m2 + emms RET %endmacro
Hi! The functions in libavutil/x86/pixelutils.asm are exported to the library users if I understand the code correctly. I suspect it can be expected that the MMX state is reset after returning. Fixes the pixelutils fate test with musl on x86-32. Please comment, Carl Eugen From f16831e6dc0f36c8f290d927bf51142c64fe8afc Mon Sep 17 00:00:00 2001 From: Carl Eugen Hoyos <cehoyos@ag.or.at> Date: Sun, 2 Oct 2016 22:45:51 +0200 Subject: [PATCH] lavu/x86/pixelutils: Call emms before returning. The functions are exported and the library user can expect that the MMX state is reset after returning. --- libavutil/x86/pixelutils.asm | 5 +++++ 1 file changed, 5 insertions(+)