[cairo] Problem compiling pixman-sse.c under Win32, blame it on MSVC !!

André Tupinambá andrelrt at gmail.com
Mon Jul 21 18:48:27 PDT 2008 

Yes, It's a really possible, but I'll test it first and check the
generated assembly (in GCC and MSVC).

If we had some slowdowns or poor compiler optimization, I will try to
change the inline functions to defines.

Regards,

André Tupinambá


On Mon, Jul 21, 2008 at 10:05 PM, Rodrigo Kumpera <kumpera at gmail.com> wrote:
> Since most of these functions force inlining, argument passing by pointer or
> by value
> should not matter, modulo compiler inability to do the right thing.
>
> I think that there are no issues from changing some args from values to regs
> as long as GCC still manages to generate decent code. From what I recall,
> this is not
> the case and some reasonable recent version of it should do the trick.
>
> Frédéric, do you mind testing that for gcc?
>
> Thanks,
> Rodrigo
>
> On Mon, Jul 21, 2008 at 6:19 AM, Antoine Azar <cairo at antoineazar.com> wrote:
>>
>> Yep, I've tried everything on my side (playing with compiler switches,
>> setting the function parameters as const references, wrapping in structs,
>> changing stack size, etc) and didn't have more luck than Fred.
>>
>> VC++ always borks starting the fourth __m128i parameter only. The three
>> first ones are always ok. It seems this is a limitation of VC++, that
>> it'll
>> only handle a "pass by register" of up to three SSE intrinsics, and not
>> one
>> more.
>>
>> I don't think sending pointers would be much of an issue: this is already
>> done at many other places in the code, and it'll avoid the overhead of
>> passing by value 16 byte data structures.
>> Otherwise, we can try rewriting functions so they always use at most 3 SSE
>> intrinsics that are passed by value, but that might be a pain.
>>
>> I'd be curious to see how the Intel Compiler handles this.
>>
>> Antoine
>>
>>
>> > -----Original Message-----
>> > From: cairo-bounces at cairographics.org
>> > [mailto:cairo-bounces at cairographics.org] On Behalf Of Frédéric Plourde
>> > Sent: Sunday, July 20, 2008 10:03 PM
>> > To: cairo at cairographics.org
>> > Subject: [cairo] Problem compiling pixman-sse.c under
>> > Win32,blame it on MSVC !!
>> >
>> > Hi !
>> >
>> >   Vlad had emailled me with this problem compiling pixman
>> > sith SSE2 stuff enabled.
>> > In fact, here are the errors that we got :
>> >
>> > pixman-sse.c
>> > pixman-sse.c(142) : error C2719: 'xmm3': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(195) : error C2719: 'alphaHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(210) : error C2719: 'alphaDstHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(210) : error C2719: 'dstLo': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(210) : error C2719: 'dstHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(210) : error C2719: 'alphaSrcLo': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(210) : error C2719: 'alphaSrcHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(246) : error C2719: 'alphaHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(276) : error C2719: 'alphaHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(276) : error C2719: 'maskLo': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(276) : error C2719: 'maskHi': formal parameter with
>> > __declspec(align('16')) won't be aligned
>> > pixman-sse.c(290) : warning C4133: 'function' : incompatible
>> > types - from '__m128i *' to 'const char *'
>> > pixman-sse.c(296) : warning C4133: 'function' : incompatible
>> > types - from '__m128i *' to 'const char *'
>> > pixman-sse.c(371) : error C2719: 'alphaSrc': formal parameter with
>> > __declspec(align('8')) won't be aligned
>> > pixman-sse.c(398) : error C2719: 'dst': formal parameter with
>> > __declspec(align('8')) won't be aligned
>> > pixman-sse.c(4432) : error C2275: '__m128i' : illegal use of
>> > this type as an expression
>> >         D:\msvs8\VC\INCLUDE\emmintrin.h(45) : see declaration
>> > of '__m128i'
>> > pixman-sse.c(4432) : error C2146: syntax error : missing ';'
>> > before identifier 'xmm0'
>> > pixman-sse.c(4432) : error C2065: 'xmm0' : undeclared identifier
>> > pixman-sse.c(4432) : error C2065: 'xmm1' : undeclared identifier
>> > pixman-sse.c(4432) : error C2065: 'xmm2' : undeclared identifier
>> > pixman-sse.c(4432) : error C2065: 'xmm3' : undeclared identifier
>> > pixman-sse.c(4434) : error C2440: '=' : cannot convert from
>> > '__m128i' to 'int'
>> > pixman-sse.c(4435) : error C2440: '=' : cannot convert from
>> > '__m128i' to 'int'
>> > pixman-sse.c(4436) : error C2440: '=' : cannot convert from
>> > '__m128i' to 'int'
>> > pixman-sse.c(4437) : error C2440: '=' : cannot convert from
>> > '__m128i' to 'int'
>> > pixman-sse.c(4439) : error C2440: 'function' : cannot convert
>> > from 'int'
>> > to '__m128i'
>> > pixman-sse.c(4439) : warning C4024: 'save128Aligned' :
>> > different types for formal and actual parameter 2
>> > pixman-sse.c(4440) : error C2440: 'function' : cannot convert
>> > from 'int'
>> > to '__m128i'
>> > pixman-sse.c(4440) : warning C4024: 'save128Aligned' :
>> > different types for formal and actual parameter 2
>> > pixman-sse.c(4441) : error C2440: 'function' : cannot convert
>> > from 'int'
>> > to '__m128i'
>> > pixman-sse.c(4441) : warning C4024: 'save128Aligned' :
>> > different types for formal and actual parameter 2
>> > pixman-sse.c(4442) : error C2440: 'function' : cannot convert
>> > from 'int'
>> > to '__m128i'
>> > pixman-sse.c(4442) : warning C4024: 'save128Aligned' :
>> > different types for formal and actual parameter 2
>> >
>> >
>> > We found the following :
>> >
>> >
>> > for every C2719 errors, the solution is to avoid passing
>> > __m128i values directly, because MSVC just doesn't allow
>> > function parameters to be of types declared with the
>> > "__declspec(align('#'))" modifier (this is the case of
>> > __m128i). See:
>> > http://msdn.microsoft.com/en-us/library/373ak2y1(VS.80).aspx
>> >
>> > More problematic is the behaviour of MSVC under these
>> > assumptions... in fact, try removing ONLY the xmm3 function
>> > parameter at line #142 in pixman-sse.c  (and by commenting
>> > references to xmm3 inside the function, of course), it will
>> > compile. (!!).  I've went through different forums for
>> > developpers and it seems there are still some bugs with those
>> > intrinsics in MSVC8. Very dissapointing!
>> >
>> > So my recommandation to misters Tupinamba and Kumpera would
>> > be to pass POINTERS to those function parameters instead...
>> > as :
>> >
>> > static inline __m128i
>> > pack565_4x128_128 (__m128i *xmm0,  __m128i *xmm1,  __m128i
>> > *xmm2, __m128i *xmm3) {
>> >    __m128i lo, hi;
>> >
>> >    lo = _mm_packus_epi16 (pack565_2x128_128 ( *xmm0, *xmm1 ),
>> > _mm_setzero_si128 ());
>> >    hi = _mm_packus_epi16 (_mm_setzero_si128 (),
>> > pack565_2x128_128 ( *xmm2, *xmm3 ));
>> >
>> >    return _mm_or_si128 (lo, hi);
>> > }
>> >
>> > compiles perfectly.
>> > However, this would maybe imply significant impacts on
>> > performance... it should be addressed and profiled..
>> >
>> >
>> > ******
>> > Besides, for the C2275 error, it's even more embarassing for
>> > microsoft... it's another case of MSVC being very capricious.
>> > In some cases, with aligned variables, MSVC doesn't allow us
>> > to declare
>> > those variable in the middle of the function... We then need
>> > to move the
>> > declaration earlier.
>> > see, at line 4432,
>> >
>> >            __m128i xmm0, xmm1, xmm2, xmm3; needs to be moved up a
>> > little... as :
>> >
>> > while (w >= 64)
>> >        {
>> >        __m128i xmm0, xmm1, xmm2, xmm3;
>> >
>> >            /* 128 bytes ahead */
>> >            cachePrefetch (((__m128i*)s) + 8);
>> >            cachePrefetch (((__m128i*)d) + 8);
>> >
>> > compiles now...
>> > ****************
>> >
>> > So here it is... a patch with those changes in pixman-sse.c
>> > I'd like you guys (especcially André) to look that over and
>> > tell me what
>> > you think.  It's a first draft, but it compiles under all 3
>> > major platforms.
>> >
>> > Best,
>> > -fred-
>> >
>>
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