On Mon, Mar 19, 2012 at 1:43 PM, Ronald S. Bultje <[email protected]> wrote: > Hi, > > On Mon, Mar 19, 2012 at 1:12 PM, Jason Garrett-Glaser <[email protected]> wrote: >> On Mon, Mar 19, 2012 at 12:25 PM, Ronald S. Bultje <[email protected]> >> wrote: >>> On Mon, Mar 19, 2012 at 12:03 PM, Jason Garrett-Glaser <[email protected]> >>> wrote: >>>> On Mon, Mar 19, 2012 at 10:14 AM, Ronald S. Bultje <[email protected]> >>>> wrote: >>>>> On Mon, Mar 19, 2012 at 9:48 AM, Jason Garrett-Glaser <[email protected]> >>>>> wrote: >>>>>> On Sat, Mar 17, 2012 at 9:34 AM, Ronald S. Bultje <[email protected]> >>>>>> wrote: >>>>>>> --- >>>>>>> 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" >>>>>>> "shl $17, %k1 \n\t" >>>>>>> "add %%eax, %%eax \n\t" >>>>>>> "sub %k1, %%eax \n\t" >>>>>>> @@ -117,7 +117,7 @@ static av_always_inline int >>>>>>> get_cabac_bypass_sign_x86(CABACContext *c, int val) >>>>>>> "sub %%edx, %%ecx \n\t" >>>>>>> "test %%ax, %%ax \n\t" >>>>>>> " jnz 1f \n\t" >>>>>>> - "mov %3, %1 \n\t" >>>>>>> + "mov %c4(%2), %1 \n\t" >>>>>>> "subl $0xFFFF, %%eax \n\t" >>>>>>> "movzwl (%1), %%edx \n\t" >>>>>>> "bswap %%edx \n\t" >>>>>>> @@ -126,11 +126,14 @@ static av_always_inline int >>>>>>> get_cabac_bypass_sign_x86(CABACContext *c, int val) >>>>>>> "addl %%edx, %%eax \n\t" >>>>>>> "mov %1, %3 \n\t" >>>>>>> "1: \n\t" >>>>>>> - "movl %%eax, %2 \n\t" >>>>>>> + "movl %%eax, %c4(%2) \n\t" >>>>>>> >>>>>>> - :"+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" >>>>>> >>>>>> IMO clobbering memory looks very very hacky, and I don't like it. If >>>>>> you need to clobber something, it'd be much better if we could clobber >>>>>> exactly what needs clobbering, and nothing more. >>>>> >>>>> Well, I don't think inline assembly supports explicitely clobbering >>>>> variables without marking them as "+m" or "+r", which messes up the >>>>> register allocator for at least gcc-4.2.1 (it uses a different >>>>> register for each "m"(c->...), thus running out of registers; yes, >>>>> there's many things wrong there). >>>> >>>> You can clobber a memory location without referencing it in the asm, >>>> and thus without allocating a register for it. >>> >>> That sounds useful, how do I do that? >> >> Just add +m arguments and don't use them, that's all. >> >> Here's an example from an unfinished patch of mine: >> >> +static ALWAYS_INLINE void x264_cabac_encode_decision( x264_cabac_t >> *cb, int i_ctx, int b ) >> +{ >> + asm( >> + "call %P8\n" >> + :"+S"(i_ctx),"+d"(b), "+D"(cb->i_range), "+m"(cb->i_low), >> "+m"(cb->i_queue), "+m"(cb->i_bytes_outstanding), "+m"(cb->p) >> + :"a"(cb),"X"(x264_cabac_encode_decision_asm) >> + :"%ecx" >> + ); >> +} > > That's how we got here in the first place. gcc-4.2.1 and clang-2.9 > allocate a register for "+m"(struct->val) pairs, causing the compiler > to run out of registers. It simply won't compile, as silly as that > sounds.
That's a compiler bug, make them fix it. Jason _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
