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Re: Processor-specific code


On Thu, Apr 14, 2005 at 10:35:06AM -0700, Richard Henderson wrote:
> On Thu, Apr 14, 2005 at 05:27:16PM +0200, Fran?ois-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.

I agree with Richard.

> 
> All that said, C99 has <fenv.h> to control just about anything you
> could want about the fpu.
> 

Does gcc support 
#pragma STDC FENV_ACCESS

-- 
Steve


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