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: >>>> 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? Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
