Re: [PATCH] Revert "cross-canadian: Handle powerpc linux verses linux-gnuspe"

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Fri, 2014-01-24 at 20:56 +0000, Phil Blundell wrote:
> On Thu, 2014-01-23 at 18:22 +0000, alexandru.sardan@freescale.com wrote:
> > [Alex Sardan] No. The more generic target powerpc-none-linux will not
> > generate SPE code and the powerpc-none-linux-gnuspe target that generates
> > SPE will not be able to generate Altivec.
> 
> Why not?  As far as I can tell from the gcc configury, the target string
> only affects the defaults (i.e. powerpc-*-linux gets -mno-spe
> -mno-altivec, powerpc-*-linuxaltivec gets -maltivec -mno-spec, and
> powerpc-*-linuxspe gets -mno-altivec -mspe).  There doesn't seem to be
> any real impact beyond this that would make the compiler binary
> fundamentally incapable of generating either type of instruction if you
> pass the appropriate options on the command line.

I had a closer look at this. The config.gcc case statements for powerpc
only appear to let you include rs6000/linuxaltivec.h or
rs6000/linuxspe.h, there doesn't appear to be a target you can pass in
to get both.

Looking at the code in those files, I don't see any reason why you can't
actually include support for both however. As such, I just hacked a
build with:

tm_file="${tm_file} rs6000/linuxaltivec.h"
tm_file="${tm_file} rs6000/linuxspe.h rs6000/e500.h"

and it certainly seems to build ok and compile things (this was just for
qemuppc). I didn't try building altivec or spe specific things but
looking at the code, I can't see any reason it wouldn't work at least in
theory.

I'd suggest the easiest way to resolve this may be to patch gcc to
include support for all the modes.

Cheers,

Richard