[Bug preprocessor/37550] Please document predefined sub-architecture support macros
pinskia at gmail dot com
gcc-bugzilla@gcc.gnu.org
Wed Sep 17 03:13:00 GMT 2008
------- Comment #1 from pinskia at gmail dot com 2008-09-17 03:12 -------
Subject: Re: New: Please document predefined sub-architecture support macros
Sent from my iPhone
On Sep 16, 2008, at 7:35 PM, "martinrb at google dot com"
<gcc-bugzilla@gcc.gnu.org
> wrote:
> The preprocessor symbol __MMX__ indicates whether this gcc
> includes mmx support. This is extremely useful, but undocumented.
> I only found out by finding the symbol in other peoples' code.
Some targets actually define this based some specifications of the
target. Spu and -mcpu=cell on powerpc define __SPU__/__PPU__ as
specified by the C/C++ language extension for the cbea document. I bet
x86 has this specified in their documentation rather than in GCC's
documentation.
>
>
> The particular symbol __MMX__ should be documented in
> the obvious place, namely where the -mmmx flag is documented
> in the x86-specific page.
>
> And of course, similarly for other such predefined flags.
> I assume there's one for sse, but I haven't actually tried to find
> out.
>
> Here's a shell transcript, again compiling my favorite
> source file, /dev/null:
>
> (martinrb@spraggett) ~ $ gcc -mmmx -E -dD -x c /dev/null | sort > /
> tmp/t1
> (martinrb@spraggett) ~ $ gcc -mno-mmx -E -dD -x c /dev/null | sort
> > /tmp/t2
> (martinrb@spraggett) ~ $ diff /tmp/t[12]
> 92d91
> < #define __MMX__ 1
>
>
> --
> Summary: Please document predefined sub-architecture support
> macros
> Product: gcc
> Version: 4.2.3
> Status: UNCONFIRMED
> Severity: normal
> Priority: P3
> Component: preprocessor
> AssignedTo: unassigned at gcc dot gnu dot org
> ReportedBy: martinrb at google dot com
> GCC host triplet: x86_64-linux-gnu
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37550
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37550
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