Re: Predefine _M_IX86 in gcc

On Sat, 21 Dec 2002, Danny Smith wrote:

> > Cosmin Truta wrote:
> > >
> > > I've just looked into the mingw specs, and I saw in the long line
> > >   "... march=i486:-D__i486 -D__i486__ ..."
> > > which can go into
> > >   "... march=i486:-D__i486 -D__i486__ -D_M_IX86=400 ..."


Earnie Boyd wrote:

> [...] However, should the macro definition be based on mcpu or march?


Danny Smith wrote:

> -march, if it is to be useful  It would then provide information on what
> insn set is available, not just how scheduling of the i386 insn set is
> tuned.  The __i386__, __i486__  predefines  are based on -march.


I wondered about this myself. Now I see: it should be -march.


Danny again:

> If this is high priority for you, you will need to provide patchset
> against GCC trunk (which will be 3.4 in about 8-9 months time).   Those
> lines in the specs file are generated from defines in i386.h in GCC
> source. I don't know if Linux and other i386 targets will will want them
> so the _M_IX86 definitions may have to go in cygwin.h or mingw.h

My original interest was actually in having GLUT working under MinGW.
_M_IX86 is a low-priority issue for me, too, but I am willing to take
care of it.

First, I plan to ask the Cygwin folks what do they think about it.
I expect they will not want it, for the same reason they don't want
-DWIN32 and -D_WIN32, but I'll ask, anyway.

I am a little busy right now. Still, I am not afraid of being late with
the submission, because gcc-3.4 is just in Stage 1, and this is a minor
patch.


Danny again:

> I like the existing GCC predifines better because they provide
> infornation on newer chips: pentium2/3/4, k6, k6-2,k6-3, athlon,
> athlon-4.  I don't know how they all equate to the _M_IX86 defines.

I don't think they do.

The existing predefines should remain of course, because they exist in
the other GCC incarnations, such as Linux, and MinGW is a GCC compiler.
_M_IX86 should be added to MinGW because it belongs to the Wintel32
platform (just as WIN32 and _WIN32 are), and MinGW is a Wintel32 compiler.


Cosmin



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