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Re: [RFA:] Fix other/14354: low precision on subnormal single FPnumbers multiplied with fp-bit.c


On Thu, 2004-03-04 at 13:57, Hans-Peter Nilsson wrote:
> Why the general confidence in sim-fpu.c over fp-bit.c? 

The last few bug fix patches I have looked at for fp-bit.c have been for
problems that were already fixed in sim-fpu.c.  This one included.

I think sim-fpu.c has gotten more testing than fp-bit.c.  fp-bit.c is
only used for soft-float targets, and people using soft-float targets
generally don't do a lot of FP because it is too slow.  sim-fpu.c
however is used for hard-float targets, and people with hard-float
targets expect FP to work correctly, and will notice when it doesn't.

> why any corrections haven't propagated, given that the GDB and
> GCC crowds have a large intersection.

I don't think there is any particular history.  I think the main problem
is that most gcc people don't know about the gdb sim-fpu.c, and most gdb
people don't know about gcc fp-bit.c.  Or maybe people know and keep
forgetting about it.

There are some interface differences between sim-fpu.c and fp-bit.c
because they are serving slightly different purposes.  So they can't be
shared as is.  It might be possible to abstract out the core routines
from the different interfaces though.

> Please excuse my denseness: I don't understand what you here
> refer to by "this".  Do you approve the patch as-is, or a patch
> adjusted to make that part be more like that in sim-fpu.c or to
> something else?

I am approving the patch as is.  I am also pointing out that more work
could be done here if someone cared.

> If you refer to a change significantly larger than the context
> of the patch, I'd rather import tege's floating-point library.

Yes, Torbjorn's soft-FP library is also a good alternative, and probably
even better than sim-fpu.c.

Also, now that the tree-ssa Fortran95 compiler requires GMP, we could
consider a soft-FP library implementation that directly uses GMP.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com


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