This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]

Re: Second Draft "Unsafe fp optimizations" project description. wrote:

> <<Obviously, it is useless to talk about the ill effects of rearranging
> floating point expressions without having a solid reference. To simplify the
> analysis below, this project confines itself to the targets that support the
> IEEE-754 Standard, using the standard rounding mode for reference.
> >>

> Once again, the IEEE-754 standard has nothing whatsoever to say about
> evaluation of floating-point expressions in high level languages.

I don't quite understand the "again" - if you wrote it before, it
certainly didn't hit my mailbox ...

Then again :-) yes I know that the IEEE-754 has nothing to say about
evaluation of floating point expressions in high level languages.  The
point is that *we* want to say something about the (differences between)
evaluations of expressions - so we better have a frame of reference.

E.g., if we want to say that optimization -fblah will cause overflow
when the inputs to the (transformed) expression are in the subset X of
all representable floating point numbers, we have to assume a model - my
suggestion is to use the IEEE-754 model.

Toon Moene - - phoneto: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
Maintainer, GNU Fortran 77:
Join GNU Fortran 95: (under construction)

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]