[Bug target/6526] [SH4] sdivsi3_i4 can clobber xd0/xd2

["marcus at mc dot pp dot se" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=6526



------- Additional Comments From marcus@mc.pp.se  2003-06-03 19:19 -------
Subject: Re:  [SH4] sdivsi3_i4 can clobber xd0/xd2


"joern.rennecke@superh.com" <gcc-bugzilla@gcc.gnu.org> writes:

> > > The patch you provided does not make integer division slower,
> > 
> > Well, that's a good thing isn't it?
> 
> Oops, scratch that 'not'.

Ah.  I did some quick measurememts and the slowdown seems to be around
3.5% for signed and 8% for unsigned division.  A little higher than I
expected actually.


> So, are you using integer division somewhere in this loop?

Not in the inner loop, which is 100% assembler code.


> Or are you doing an uneven number of iterations, so you end up
> with a switched register set at the end?

Yup.  And the "end" can be followed by more iterations later, after I
have done some integer operations (modulus).  An outer loop, if you
will.  I did some attempts with adding extra switches to "balance" the
thing, but it all turned out far to messy.


  // Marcus






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