sqrt on alphaev6

[Toon Moene]

Brad Lucier wrote:

> with -mcpu=ev6 -mieee on alphaev6 with gcc 2.95.1 the following code
> is typically generated for sqrt:

>         sqrttsu $f16,$f0
>         cmpteqsu $f0,$f0,$f10      ; check for NaN?
>         fbne $f10,$L836
>         jsr $26,sqrt
>         ldgp $29,0($26)
> $L836:

> My question is whether the call to the sqrt routines is necessary
> for ev6.  I find 21264hrm.pdf to be somewhat confusing, but it
> seems to imply that software completion is not needed on the 21264.

According to the documentation accompanying gcc, one can specify the
following macro name for any target architecture (cpu/os combination):

`TARGET_EDOM'
     The value of `EDOM' on the target machine, as a C integer constant
     expression.  If you don't define this macro, GNU CC does not
     attempt to deposit the value of `EDOM' into `errno' directly.
     Look in `/usr/include/errno.h' to find the value of `EDOM' on your
     system.

     If you do not define `TARGET_EDOM', then compiled code reports
     domain errors by calling the library function and letting it
     report the error.  If mathematical functions on your system use
     `matherr' when there is an error, then you should leave
     `TARGET_EDOM' undefined so that `matherr' is used normally.

This constant is not defined for many targets:

[toon@moene config]$ grep TARGET_EDOM */*.h
arm/linux-aout.h:#define TARGET_EDOM 33
arm/riscix.h:#define TARGET_EDOM 33
sparc/sparc.h:#define TARGET_EDOM 33

HTH,

PS: As this has no relevance for other languages than those in the C
    family, the Fortran Frontend causes this call to sqrt *not* to be
    generated.

-- 
Toon Moene (toon@moene.indiv.nluug.nl)
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
Phone: +31 346 214290; Fax: +31 346 214286
GNU Fortran: http://world.std.com/~burley/g77.html