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Re: Processor-specific code
On Thu, 2005-04-14 at 18:35, Richard Henderson wrote:
> On Thu, Apr 14, 2005 at 05:27:16PM +0200, François-Xavier Coudert wrote:
> > No, since reading GFORTRAN_FPU_* variables changes the FPU mode when the
> > library is loaded, while TR 15580 commands will be ran afterwards (during
> > execution).
>
> You'll find that globally changing the rounding mode will screw up
> libm functions. Which is pretty much going to make this useless.
>
> Further, when folks need rounding modes other than round-to-nearest,
> they tend to need to switch rounding modes during the program too.
> For instance, to perform the same calculation with both round-up and
> round-down to get error bounds on the calculation.
>
> Thus I think an environment variable to do this is doubly useless.
Not all environments can change the rounding mode dynamically. For
example, on the FPA co-processor for ARM, rounding is set by the
instruction selected -- so the concept of having an environment variable
to control this is meaningless.
R.