Re: IEEE inexact-flag not working on the Alpha (despite -mieee-with-inexact)?

[Roberto Bagnara <bagnara at cs dot unipr dot it>]

Tim Prince wrote:
> Roberto Bagnara wrote:
>
> > #include <fenv.h>
> > #include <cstdio>
> >
> > int main() {
> >   float x = 2;
> >   float y = 3;
> >   feclearexcept(FE_INEXACT);
> >   x = x / y;
> >   printf("%d %.1000g\n", fetestexcept(FE_INEXACT) != 0, x);
> > }
>
> Is this a way of testing whether the division is performed at compile
> time?  Do you call it a bug if constant propagation occurs when you don't
> take action to prevent it?

Hi Tim,

I am not sure I understand your message.  However, before mailing I did
check that constant propagation is not an issue by checking the generated
assembly:

        ldq $27,feclearexcept($29)              !literal!2
        jsr $26,($27),0         !lituse_jsr!2
        ldah $29,0($26)         !gpdisp!3
        lda $29,0($29)          !gpdisp!3
        lds $f11,20($15)
        lds $f10,16($15)
        divs/sui $f11,$f10,$f12
        trapb
        cpys $f12,$f12,$f10
        sts $f10,20($15)
        ldah $16,32($31)
        ldq $27,fetestexcept($29)               !literal!4
        jsr $26,($27),0         !lituse_jsr!4

Note that I am not compiling with optimizations and that the
divs/sui opcode is generated.
All the best,

    Roberto

--
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara@cs.unipr.it