Hi, 2012/3/19 Måns Rullgård <[email protected]>: > "Ronald S. Bultje" <[email protected]> writes: >> 2012/3/19 Måns Rullgård <[email protected]>: >>> "Ronald S. Bultje" <[email protected]> writes: >>>> 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. >>> >>> Your compiler seems to be the only one where it gives better code. >>> There is no guarantee that your compiler will keep doing this next time >>> you upgrade it. Since I can't reproduce the problem, I'm not in a very >>> good position to figure out why it happens. >> >> My compiler has been like that for years. >> >>> You can, and you're the one >>> pushing for these patches, so the work falls to you. Tough luck. >> >> You're not very clear on what you want. You want the holy grail? You >> want a time machine? You want a better pension? What falls on me? I've >> written code that is (if I understand you correctly) the same for you, >> and better for me. That's fantastic! So does that mean we agree I can >> commit it? If not, what exactly is your problem with this code? > > You've made changes that have very unexpected results. This is never a > good thing unless the reasons are understood.
Yes: the compiler screwed up, and I fixed it. Now, this isn't going anywhere. What are you looking for? I need a concrete thing that you intend me to do, else I'll simply have to commit as-is. Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
