Re: fcmove on Alpha not qualified with /su when compiling -mieee - is that correct ?

[Toon Moene <toon at moene dot indiv dot nluug dot nl>]

Richard Henderson wrote:

> To start, there is no fcmov variant that includes qualifiers.

Ah, well, that explains ....

> > So the obvious question is: Why do I get an exception on a denormal
> > number while I compiled all the stuff with -mieee ?
> 
> You shouldn't have gotten one.

Great !

> The non-obvious question is what operating system and kernel version
> are you running?  Even with the /su qualifier, the instruction does
> still trap, but it's supposed to be fixed up in the kernel and the
> program restarted.  Clearly that's not happening.

It's the kernel in Red Hat 6.0 for Alpha (2.2.5-something).

> There have been bugs in even moderately recent Linux kernels,
> some of which only showed up on EV6, which you're clearly running.
> If you're using a Linux kernel older than 2.2.16, I recommend
> that you upgrade.

Hmmmm, fascinating - let's see if I can compile my own kernel ;-)

BTW, so what you're saying is:  It is immaterial whether you specify
-mieee w.r.t. denormals.  That's interesting, because I managed to
"cure" several fpe's in our code by just compiling it with -mieee 1). 
Perhaps that was just a fortuitous side-effect.

1) Aside from the fact that I repaired a number of utterly non-physical
assumptions, like a water vapor saturation pressure table starting from
13 K ...

Thanks for the explanation !

-- 
Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
GNU Fortran 77: http://gcc.gnu.org/onlinedocs/g77_news.html
GNU Fortran 95: http://g95.sourceforge.net/ (under construction)