On Wed, Sep 17, 2014 at 09:21:08PM +0200, Vitor Sessak wrote: > Hi! > > I'm not sure we can count on registers been preserved across ASM > blocks. Moreover, this causes problems with utils that instrument the > code by inserting function calls between lines (like ThreadSanitizer). > > The attached patch fix one instance of this problem in swscale. > > -Vitor
> swscale.c | 82
> +++++++++++++++++++++++++++++++-------------------------------
> 1 file changed, 42 insertions(+), 40 deletions(-)
> 7fe9f7a0c1a7c1ed843b891f5f810fbd94a2e03f
> 0001-swscale-x86-do-not-expect-registers-to-be-preserved-.patch
> From f1c59628b2baeb9994bed8947c0a2c228610bf4f Mon Sep 17 00:00:00 2001
> From: Vitor Sessak <vses...@google.com>
> Date: Wed, 17 Sep 2014 21:10:16 +0200
> Subject: [PATCH] swscale/x86: do not expect registers to be preserved across
> inline ASM blocks
>
> ---
> libswscale/x86/swscale.c | 82
> +++++++++++++++++++++++++-----------------------
> 1 file changed, 42 insertions(+), 40 deletions(-)
>
> diff --git a/libswscale/x86/swscale.c b/libswscale/x86/swscale.c
> index c4c0e28..38157c8 100644
> --- a/libswscale/x86/swscale.c
> +++ b/libswscale/x86/swscale.c
> @@ -205,36 +205,19 @@ static void yuv2yuvX_sse3(const int16_t *filter, int
> filterSize,
> yuv2yuvX_mmxext(filter, filterSize, src, dest, dstW, dither, offset);
> return;
> }
> - if (offset) {
> - __asm__ volatile("movq (%0), %%xmm3\n\t"
> - "movdqa %%xmm3, %%xmm4\n\t"
> - "psrlq $24, %%xmm3\n\t"
> - "psllq $40, %%xmm4\n\t"
> - "por %%xmm4, %%xmm3\n\t"
> - :: "r"(dither)
> - );
> - } else {
> - __asm__ volatile("movq (%0), %%xmm3\n\t"
> - :: "r"(dither)
> - );
> - }
> - filterSize--;
not sure i missed it but it seems this is lost in teh new code
> - __asm__ volatile(
> - "pxor %%xmm0, %%xmm0\n\t"
> - "punpcklbw %%xmm0, %%xmm3\n\t"
> - "movd %0, %%xmm1\n\t"
> - "punpcklwd %%xmm1, %%xmm1\n\t"
> - "punpckldq %%xmm1, %%xmm1\n\t"
> - "punpcklqdq %%xmm1, %%xmm1\n\t"
> - "psllw $3, %%xmm1\n\t"
> - "paddw %%xmm1, %%xmm3\n\t"
> - "psraw $4, %%xmm3\n\t"
> - ::"m"(filterSize)
> - );
> - __asm__ volatile(
> - "movdqa %%xmm3, %%xmm4\n\t"
> - "movdqa %%xmm3, %%xmm7\n\t"
> - "movl %3, %%ecx\n\t"
> +#define MAIN_FUNCTION \
> + "pxor %%xmm0, %%xmm0 \n\t" \
> + "punpcklbw %%xmm0, %%xmm3 \n\t" \
> + "movd %4, %%xmm1 \n\t" \
> + "punpcklwd %%xmm1, %%xmm1 \n\t" \
> + "punpckldq %%xmm1, %%xmm1 \n\t" \
> + "punpcklqdq %%xmm1, %%xmm1 \n\t" \
> + "psllw $3, %%xmm1 \n\t" \
> + "paddw %%xmm1, %%xmm3 \n\t" \
> + "psraw $4, %%xmm3 \n\t" \
> + "movdqa %%xmm3, %%xmm4 \n\t" \
> + "movdqa %%xmm3, %%xmm7 \n\t" \
> + "movl %3, %%ecx \n\t" \
> "mov %0, %%"REG_d" \n\t"\
> "mov (%%"REG_d"), %%"REG_S" \n\t"\
> ".p2align 4 \n\t" /* FIXME
> Unroll? */\
> @@ -252,20 +235,39 @@ static void yuv2yuvX_sse3(const int16_t *filter, int
> filterSize,
> " jnz 1b \n\t"\
> "psraw $3, %%xmm3 \n\t"\
> "psraw $3, %%xmm4 \n\t"\
> - "packuswb %%xmm4, %%xmm3 \n\t"
> - "movntdq %%xmm3, (%1, %%"REG_c")\n\t"
> + "packuswb %%xmm4, %%xmm3 \n\t"\
> + "movntdq %%xmm3, (%1, %%"REG_c")\n\t"\
> "add $16, %%"REG_c" \n\t"\
> "cmp %2, %%"REG_c" \n\t"\
> - "movdqa %%xmm7, %%xmm3\n\t"
> - "movdqa %%xmm7, %%xmm4\n\t"
> + "movdqa %%xmm7, %%xmm3 \n\t" \
> + "movdqa %%xmm7, %%xmm4 \n\t" \
> "mov %0, %%"REG_d" \n\t"\
> "mov (%%"REG_d"), %%"REG_S" \n\t"\
> - "jb 1b \n\t"\
> - :: "g" (filter),
> - "r" (dest-offset), "g" ((x86_reg)(dstW+offset)), "m" (offset)
> - : XMM_CLOBBERS("%xmm0" , "%xmm1" , "%xmm2" , "%xmm3" , "%xmm4" ,
> "%xmm5" , "%xmm7" ,)
> - "%"REG_d, "%"REG_S, "%"REG_c
> - );
> + "jb 1b \n\t"
> +
> + if (offset) {
> + __asm__ volatile(
> + "movq %5, %%xmm3 \n\t"
> + "movdqa %%xmm3, %%xmm4 \n\t"
> + "psrlq $24, %%xmm3 \n\t"
> + "psllq $40, %%xmm4 \n\t"
> + "por %%xmm4, %%xmm3 \n\t"
> + MAIN_FUNCTION
> + :: "g" (filter),
> + "r" (dest-offset), "g" ((x86_reg)(dstW+offset)), "m" (offset),
> + "m"(filterSize), "m"(((uint64_t *) dither)[0])
> + : "%"REG_d, "%"REG_S, "%"REG_c
> + );
you lost the XMM_CLOBBERS()
> + } else {
> + __asm__ volatile(
> + "movq %5, %%xmm3 \n\t"
> + MAIN_FUNCTION
> + :: "g" (filter),
> + "r" (dest-offset), "g" ((x86_reg)(dstW+offset)), "m" (offset),
> + "m"(filterSize), "m"(((uint64_t *) dither)[0])
> + : "%"REG_d, "%"REG_S, "%"REG_c
> + );
tabs
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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