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Re: ARM iwmmxt CFLAGS

From: Ian Lance Taylor <iant at google dot com>
To: Matt Turner <mattst88 at gmail dot com>
Cc: gcc-help at gcc dot gnu dot org
Date: Thu, 14 Jul 2011 11:53:48 -0700
Subject: Re: ARM iwmmxt CFLAGS
References: <CAEdQ38GK8WHKZcnF9RQv+nupyTYFp9_AZxF_hMfgCWitHr6XqQ@mail.gmail.com>

Matt Turner <mattst88@gmail.com> writes:

> I'm a bit confused about how CFLAGS related to ARM's iwmmxt
> instruction set extensions are handled.
>
> On x86 to enable SSEx instructions, one would do something like
> -march=... -msse3, but on ARM I must do something like -march=iwmmxt
> (where I'd have expected -march=armv7 -miwmmxt).
>
> What flags would I use to optimize code for armv7 while enabling
> iwmmxt instructions? -march=armv7 -mcpu=iwmmxt?

I think -march=iwmmxt -mtune=armv7.

I agree that this seems a bit odd.


> Also, do I need to do anything with -mabi=iwmmxt? I think not, but..

I don't know.

Ian

References:
- ARM iwmmxt CFLAGS
  - From: Matt Turner

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