[FFmpeg-devel] [PATCH 6/8] x86inc: reduce difference to x264 upstream

[James Almer]

On 11/6/2017 4:56 PM, James Darnley wrote:
> On 2017-10-31 04:30, Michael Niedermayer wrote:
>> On Mon, Oct 30, 2017 at 02:08:33PM +0100, James Darnley wrote:
>>> These changes were commited to x264 in b568a256 "Experimental nasm
>>> support"
>>> ---
>>>  libavutil/x86/x86inc.asm | 16 ++++++++++++++--
>>>  1 file changed, 14 insertions(+), 2 deletions(-)
>>
>> breaks build:
>>
>> libavcodec/x86/rv34dsp.asm:211: error: parser: instruction expected
>> libavcodec/x86/rv34dsp.asm:211: error: label or instruction expected at start of line
>> libavcodec/x86/rv34dsp.asm:213: error: parser: instruction expected
>> libavcodec/x86/rv34dsp.asm:213: error: label or instruction expected at start of line
>> make: *** [libavcodec/x86/rv34dsp.o] Error 1
>> make: *** Waiting for unfinished jobs....
>>
>> NASM version 2.10.09 compiled on Dec 29 2013
> 
> This is very weird.  I have reproduced it on 2.13.01 on my server but I
> couldn't on my laptop.  After a `make distclean` I can.  I think that is
> the bug with nasm not listing includes as dependencies so I wasn't
> rebuilding those objects.
> 
>> libavcodec/x86/rv34dsp.asm:211: error: parser: instruction expected
>> libavcodec/x86/rv34dsp.asm:173: ... from macro `RV34_IDCT_DC_ADD' defined here
>> libavutil/x86/x86inc.asm:707: ... from macro `cglobal' defined here
>> libavutil/x86/x86inc.asm:733: ... from macro `cglobal_internal' defined here
>> libavcodec/x86/rv34dsp.asm:211: error: label or instruction expected at start of line
>> libavcodec/x86/rv34dsp.asm:173: ... from macro `RV34_IDCT_DC_ADD' defined here
>> libavutil/x86/x86inc.asm:707: ... from macro `cglobal' defined here
>> libavutil/x86/x86inc.asm:733: ... from macro `cglobal_internal' defined here
>> libavcodec/x86/rv34dsp.asm:213: error: parser: instruction expected
>> libavcodec/x86/rv34dsp.asm:173: ... from macro `RV34_IDCT_DC_ADD' defined here
>> libavutil/x86/x86inc.asm:707: ... from macro `cglobal' defined here
>> libavutil/x86/x86inc.asm:733: ... from macro `cglobal_internal' defined here
>> libavcodec/x86/rv34dsp.asm:213: error: label or instruction expected at start of line
>> libavcodec/x86/rv34dsp.asm:173: ... from macro `RV34_IDCT_DC_ADD' defined here
>> libavutil/x86/x86inc.asm:707: ... from macro `cglobal' defined here
>> libavutil/x86/x86inc.asm:733: ... from macro `cglobal_internal' defined here
> 
> Line 733 is the align command to align the start of the function.  I
> can't see why it fails here but not on any other function in that file
> or any other file.
> 
> After some cutting and pasting there is something about the mmxext
> function on line 159.  Cutting it out with the following diff, and
> building it will succeed.
> 
>> diff --git a/libavcodec/x86/rv34dsp.asm b/libavcodec/x86/rv34dsp.asm
>> index 692b4acfcd..3448f82e75 100644
>> --- a/libavcodec/x86/rv34dsp.asm
>> +++ b/libavcodec/x86/rv34dsp.asm
>> @@ -156,17 +156,6 @@ cglobal rv34_idct_dc_add, 3, 3
>>      packuswb     %2, %2
>>      movd         %1, %2
>>  %endmacro
>> -INIT_MMX mmxext
>> -cglobal rv34_idct_add, 3,3,0, d, s, b
>> -    ROW_TRANSFORM       bq
>> -    COL_TRANSFORM     [dq], mm0, [pw_col_coeffs+ 0], [pw_col_coeffs+ 8]
>> -    mova               mm0, [pw_col_coeffs+ 0]
>> -    COL_TRANSFORM  [dq+sq], mm4, mm0, [pw_col_coeffs+ 8]
>> -    mova               mm4, [pw_col_coeffs+ 8]
>> -    lea                 dq, [dq + 2*sq]
>> -    COL_TRANSFORM     [dq], mm6, mm0, mm4
>> -    COL_TRANSFORM  [dq+sq], mm7, mm0, mm4
>> -    ret
>>
>>  ; ff_rv34_idct_dc_add_sse4(uint8_t *dst, int stride, int dc);
>>  %macro RV34_IDCT_DC_ADD 0
> 
> I honestly have no idea why that causes a problem for the following
> function.  I thought it might be the lower-case ret rather than the
> upper-case RET macro but changing it doesn't change the error.

Try compiling with

make libavcodec/x86/rv34dsp.dbg.asm DBG=1
make libavcodec/x86/rv34dsp.dbg.o DBG=1

To bypass all the macro obfuscation and get errors pointing to the exact
problematic line in the preprocessed .dbg.asm file