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Re: GCC floating point usage
- From: Jeff Law <law at porcupine dot cygnus dot com>
- To: Richard Henderson <rth at redhat dot com>
- Cc: Zack Weinberg <zack at codesourcery dot com>, Mark Mitchell <mark at codesourcery dot com>, Mike Stump <mrs at apple dot com>, Geoff Keating <geoffk at geoffk dot org>, "steby at enea dot se" <steby at enea dot se>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Mon, 21 Oct 2002 10:54:53 -0600
- Subject: Re: GCC floating point usage
- Reply-to: law at redhat dot com
In message <20021016234620.GH30823@redhat.com>, Richard Henderson writes:
>Arrange for REG_CLASS_FROM_LETTER to return NO_REGS for 'f'
>when appropriate would be one way. Mistakes here would result
>in reload aborts, since reload would fail to find a way to
>move data between, into, or out of the FP regs.
>
>Marking the fp registers to be fixed for the duration of the
>function would be another way, though it would seem that you'd
>need a new hook run from rest_of_compilation, somewhere before
>regclass/reload, in order to make this work.
We used (still?) do the latter on a function-wide basis on at least
the PA port to prevent FP resources from ever being used when compiling
kernels and the like.
The only downside was you got an unfriendly abort if something went wrong.
It shouldn't be terribly hard to be able to make fixed_regs vary on a
function by function basis if indeed this is what folks want to do.
jeff
>
>
>r~