mmx.h

[Maximillian Murphy <m at de-minimis dot co dot uk>]

Dear All,

On the web there are a number of .h files that provide wrappers for mmx assembler commands.  They are usually but not always called mmx.h.  An example is here:

http://webcvs.freedesktop.org/gstreamer/gstreamer/include/mmx.h?revision=1.2&content-type=text%2Fplain&pathrev=1.2

and:

http://aggregate.org/SWAR/ars-swar.h

In there, for instance, pmullw_r2r(mm1,mm3) is defined as a macro so that it can be called as if it were a C function.  Actually it performs the assembler command pmullw on mmx registers 1 & 3.

These header files seem to be entirely generic but as far as I can see they are not shipped in any of the debian developer packages.  Does any of you use such header files?  They seem a good idea.  Is there a reason why they are not shipped as standard with gcc/debian?  Are there similar wrappers for SSE2 commands?  My processor doesn't support SSE3 or later, but information about future trends would be good to know too.

I may of course be wrong in saying that such a set of macros is not normally shipped.  I've grepped /usr/include and found nothing similar.  There is an <asm/mmx.h> header file but it is quite different and including it doesn't seem to allow assembler functions to be used:

>From the website above:

	Usage:  let's say you want to add the 64-bit vector of
	two 32-bit floats at x into register 7.  Unless you have
	declared x as "mmx_t x;" you need to cast x to the
	correct type.  Register 7 is called "mm7".  Thus:

	pfadd_m2r(*((mmx_t *) &x), mm7);

Looking at some of the few clean examples of this being used that I can find it seems that register names such as mm7 don't need to be declared - presumably they are defined somewhere in the tree of header files.

In my code:

#include <asm/mmx.h>
....
pmullw_r2r(mm0,mm1);

Compiling, or rather failing to compile:

2008.02_try001$ gcc dot_002.c 
dot_002.c: In function âmainâ:
dot_002.c:48: error: âmm0â undeclared (first use in this function)
dot_002.c:48: error: (Each undeclared identifier is reported only once
dot_002.c:48: error: for each function it appears in.)
dot_002.c:48: error: âmm1â undeclared (first use in this function)
2008.02_try001$ 

Any information on this would be welcome.

Regards, Max.