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Re: [PATCH] Add fma support to the middle end and powerpc
- From: Richard Henderson <rth at redhat dot com>
- To: Michael Meissner <meissner at linux dot vnet dot ibm dot com>, gcc-patches at gcc dot gnu dot org, dje dot gcc at gmail dot com
- Date: Thu, 14 Oct 2010 07:57:50 -0700
- Subject: Re: [PATCH] Add fma support to the middle end and powerpc
- References: <20101013213202.GA18536@hungry-tiger.westford.ibm.com>
On 10/13/2010 02:32 PM, Michael Meissner wrote:
> Since the rs6000 is the only port (so far) that provides fma and fmaf, it was
> simpler to define the macros in the backend, rather than come up with some
> callback mechanism where either c-cppbuiltin calls the rtl layer to ask if it
> has fma, or the rtl layer uses a target hook to define the macros if the
> preprocessor is loaded.
That's a bit short sighted. There's plenty of ports that already have
fma instructions in their machine description. Within the week I would
expect most of them to have been converted to your new interface.
Frankly I don't see what's so holy about c-cppbuiltin that it can't
have access to tm.h.
> +;; Fused multiply add. By default expand the FMA into (plus (mult)) to help
> +;; loop unrolling.
Er.. Really? What does loop unrolling care?
r~