Hello, as The bug isn't solved in current unstable 0.cvs20050811-2 yet, I've updated the patch against the Debian sources (see attachment).
1) The push/pop statements in the first change to mpegvideo_mmx_template.c are unnecessary, because REG_a will not be used before it gets loaded with the constant -128 - therefore no reason to back it up 2) In the second change to megvideo_mmx.template.c, you backed up REG_a with push, loaded it with the second argument, but then in movq the old value of REG_a is needed to correctly address qmat[i] - this change to the upstream source is a bug! I've solved this by adding the array start address (2'nd parameter = "m" qmat+64) to the index (REG_a), then accessing qmat[i] and afterwards subtracting the start address again - push/pop shouldn't be used here anyway, because gcc might address memory operands through %esp, so modifying the stack pointer with push/pop is not gueranteed to work under all conditions 3) Introducing the const qmat2 = qmat+64 doesn't make very much sense to me - why has this been done? Regards, Tobias
diff -Nur ffmpeg-0.cvs20050811/libavcodec/i386/mpegvideo_mmx_template.c ffmpeg-0.cvs20050811-bug#318493/libavcodec/i386/mpegvideo_mmx_template.c
--- ffmpeg-0.cvs20050811/libavcodec/i386/mpegvideo_mmx_template.c 2005-09-04 11:24:05.000000000 +0200
+++ ffmpeg-0.cvs20050811-bug#318493/libavcodec/i386/mpegvideo_mmx_template.c 2005-09-04 13:08:59.000000000 +0200
@@ -96,10 +96,8 @@
"pxor %%mm7, %%mm7 \n\t" // 0
"pxor %%mm4, %%mm4 \n\t" // 0
#if defined(PIC) && !defined(ARCH_X86_64)
- "push %%"REG_a" \n\t"
"movl %2, %%"REG_a" \n\t"
"movq (%%"REG_a"), %%mm5 \n\t" // qmat[0]
- "pop %%"REG_a" \n\t"
#else
"movq (%2), %%mm5 \n\t" // qmat[0]
#endif
@@ -153,7 +151,6 @@
: "g" (s->max_qcoeff)
);
}else{ // FMT_H263
- const uint16_t *qmat2 = qmat+64;
asm volatile(
"movd %%"REG_a", %%mm3 \n\t" // last_non_zero_p1
SPREADW(%%mm3)
@@ -170,12 +167,11 @@
"movq (%3, %%"REG_a"), %%mm6 \n\t" // bias[0]
"paddusw %%mm6, %%mm0 \n\t" // ABS(block[i]) + bias[0]
#if defined(PIC) && !defined(ARCH_X86_64)
- "push %%"REG_a" \n\t"
- "movl %2, %%"REG_a" \n\t"
- "movq (%%"REG_a", %%"REG_a"), %%mm5 \n\t" // qmat[i]
- "pop %%"REG_a" \n\t"
+ "addl %2, %%"REG_a" \n\t"
+ "movq (%%"REG_a"), %%mm5 \n\t" // qmat[i]
+ "subl %2, %%"REG_a" \n\t"
#else
- "movq (%2, %%"REG_a"), %%mm5 \n\t" // qmat[i]
+ "movq (%2, %%"REG_a"), %%mm5 \n\t" // qmat[i]
#endif
"pmulhw %%mm5, %%mm0 \n\t" // (ABS(block[i])*qmat[0] + bias[0]*qmat[0])>>16
"por %%mm0, %%mm4 \n\t"
@@ -199,7 +195,7 @@
"movzb %%al, %%"REG_a" \n\t" // last_non_zero_p1
: "+a" (last_non_zero_p1)
#if defined(PIC) && !defined(ARCH_X86_64)
- : "r" (block+64), "m" (qmat2), "r" (bias+64),
+ : "r" (block+64), "m" (qmat+64), "r" (bias+64),
#else
: "r" (block+64), "r" (qmat+64), "r" (bias+64),
#endif
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