Hi, 2012/3/19 Måns Rullgård <[email protected]>: > "Ronald S. Bultje" <[email protected]> writes: >> On Sat, Mar 17, 2012 at 11:57 AM, Ronald S. Bultje <[email protected]> >> wrote: >>> 2012/3/17 Måns Rullgård <[email protected]>: >>>> "Ronald S. Bultje" <[email protected]> writes: >>>> >>>>> --- >>>>> libavcodec/x86/cabac.h | 17 ++++++++++------- >>>>> 1 files changed, 10 insertions(+), 7 deletions(-) >>>>> >>>>> diff --git a/libavcodec/x86/cabac.h b/libavcodec/x86/cabac.h >>>>> index 3c3652d..c4832c3 100644 >>>>> --- a/libavcodec/x86/cabac.h >>>>> +++ b/libavcodec/x86/cabac.h >>>>> @@ -105,8 +105,8 @@ static av_always_inline int >>>>> get_cabac_bypass_sign_x86(CABACContext *c, int val) >>>>> { >>>>> x86_reg tmp; >>>>> __asm__ volatile( >>>>> - "movl %4, %k1 \n\t" >>>>> - "movl %2, %%eax \n\t" >>>>> + "movl %c5(%2), %k1 \n\t" >>>>> + "movl %c3(%2), %%eax \n\t" >>>> >>>> %c5? Last I checked, the code to get a plain number was 'a'. >>> >>> Fixed. >>> >>>>> - :"+c"(val), "=&r"(tmp), "+m"(c->low), "+m"(c->bytestream) >>>>> - :"m"(c->range) >>>>> - : "%eax", "%edx" >>>>> + : "+c"(val), "=&r"(tmp) >>>>> + : "r"(c), >>>>> + "i"(offsetof(CABACContext, low)), >>>>> + "i"(offsetof(CABACContext, bytestream)), >>>>> + "i"(offsetof(CABACContext, range)) >>>>> + : "%eax", "%edx", "memory" >>>> >>>> We changed this to use "m" operands to avoid the memory clobber. I know >>>> why you're doing this, but I think it's the wrong approach. >>> >>> It generates better code (less instructions for e.g. >>> decode_cabac_mb_mvd()) with gcc-4.2.1 (which is shipped with XCode). >>> Does it generate worse code anywhere? (It's true that later on it adds >>> instructions for the overread protection again, but this commit in >>> isolation makes things better, not worse.) >> >> Ping, are there any practical concerns left? > > We're still no closer to understanding what really is going on here.
You'll have to be more practical than "I don't get it, so let's do nothing". Do something to understand it. This patchset improves things on my end (better code, compiler doesn't bomb out on adding extra argument such as bytestream_end), which is more than sufficient. Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
