[Bug target/29845] sh floating point emulation is inefficient

[amylaar at gcc dot gnu dot org]

------- Comment #7 from amylaar at gcc dot gnu dot org  2007-02-01 03:41 -------
(In reply to comment #4)
> Hereattached a patch to fix a few problems:
> 
> 1) Rounding to nearest must be infinity if the "infinitely precise result has a
> magniture at least 2 exp Emax (2-2exp-p)" (ansi 754/1985 sect 4.1). The
> implementation for addsf3 and adddf3 returned a NaN.

Not always a NaN, but it's a bug regardless.  Good catch.
However, this:

 LOCAL(inf):
+       mov     #0,DBLRL

negatively impacts sh3 MA unit scheduling.

It might be an idea to align LOCAL(pos_difference_0) for sh3.


-       tst     r7,r0
+       tst     r7,r0           

You have to be careful with the whitespace.

> 2) Infinity in divsf3.S was not set (case of 1.0/0.0).

>         * config/sh/IEEE-754/m3/divsf3.S: Intialize xff000000 label.
> 
This was supposed to be:

LOCAL(m1):      .word -1
        .balign 4
LOCAL(xff000000):
#ifdef __LITTLE_ENDIAN__
 .word 0
LOCAL(xff00):   .word 0xff00
#else
LOCAL(xff00):   .word 0xff00
 .word 0
#endif

saving four bytes over using unshared constants.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29845