2018-11-26 23:35 GMT+01:00, Michael Niedermayer <mich...@niedermayer.cc>: > On Mon, Nov 26, 2018 at 12:45:26AM +0100, Carl Eugen Hoyos wrote: >> 2018-11-25 16:17 GMT+01:00, Lauri Kasanen <c...@gmx.com>: >> > Hi, >> > >> > The lone power8 fate failing test seems like an aliasing issue. >> > I've isolated it into the attached standalone test case. Compiling it >> > with >> > gcc -std=c11 -maltivec -mabi=altivec -mvsx -O3 -fno-tree-vectorize >> > -o test test.c >> > >> > reproduces on gcc 8.2.0, dropping the optimization level fixes it. This >> > was one of the "adding a printf made it work" things too. >> > >> > -Wstrict-aliasing=1 complains about the "register int *idataptr = >> > (int*)dataptr;" cast. If I put "typedef int __attribute__((may_alias)) >> > int_alias;" at the top and change the cast and type to int_alias, the >> > results become correct. >> >> Thank you for the analysis! >> >> Patch attached, Carl Eugen > >> jrevdct.c | 17 +++++++++-------- >> 1 file changed, 9 insertions(+), 8 deletions(-) >> fef3d295836588ff8e619d4aa42247b4d2f25e93 >> 0001-lavc-jrevdct-Avoid-an-aliasing-violation.patch >> From e5403b832f2bcd360128d9986b602484e576c931 Mon Sep 17 00:00:00 2001 >> From: Carl Eugen Hoyos <ceffm...@gmail.com> >> Date: Mon, 26 Nov 2018 00:43:46 +0100 >> Subject: [PATCH] lavc/jrevdct: Avoid an aliasing violation. >> >> Fixes fate on different PowerPC systems with some compilers. >> >> Analyzed-by: Lauri Kasanen >> --- >> libavcodec/jrevdct.c | 17 +++++++++-------- >> 1 file changed, 9 insertions(+), 8 deletions(-) >> >> diff --git a/libavcodec/jrevdct.c b/libavcodec/jrevdct.c >> index 3b15a52..c749468 100644 >> --- a/libavcodec/jrevdct.c >> +++ b/libavcodec/jrevdct.c >> @@ -63,6 +63,7 @@ >> */ >> >> #include "libavutil/common.h" >> +#include "libavutil/intreadwrite.h" >> >> #include "dct.h" >> #include "idctdsp.h" >> @@ -234,7 +235,7 @@ void ff_j_rev_dct(DCTBLOCK data) >> * row DCT calculations can be simplified this way. >> */ >> >> - register int *idataptr = (int*)dataptr; >> + register uint8_t *idataptr = (uint8_t*)dataptr; >> >> /* WARNING: we do the same permutation as MMX idct to simplify the >> video core */ >> @@ -254,10 +255,10 @@ void ff_j_rev_dct(DCTBLOCK data) >> int16_t dcval = (int16_t) (d0 * (1 << PASS1_BITS)); >> register int v = (dcval & 0xffff) | ((dcval * (1 << 16)) & >> 0xffff0000); >> >> - idataptr[0] = v; >> - idataptr[1] = v; >> - idataptr[2] = v; >> - idataptr[3] = v; >> + AV_WN32(&idataptr[ 0], v); >> + AV_WN32(&idataptr[ 4], v); >> + AV_WN32(&idataptr[ 8], v); >> + AV_WN32(&idataptr[12], v); > > this probably should be AV_WN32A()
Tested and applied with AV_WN32A(). Thank you, Carl Eugen _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel