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Re: State of m68k float emulation in lb1sf68.asm (muldf, divdf)
- From: Jim Wilson <wilson at specifixinc dot com>
- To: tm_gccmail at kloo dot net
- Cc: Pavel Pisa <pisa at cmp dot felk dot cvut dot cz>, gcc at gcc dot gnu dot org
- Date: 17 Nov 2003 11:52:53 -0800
- Subject: Re: State of m68k float emulation in lb1sf68.asm (muldf, divdf)
- References: <Pine.LNX.4.21.0311171109470.26432-100000@mail.kloo.net>
On Mon, 2003-11-17 at 11:16, tm_gccmail@kloo.net wrote:
> Uh, have you looked at fp-bit.c? It's glacially slow.
Have you looked at lb1sf68.asm? The complaint was that it is slow
because it is using bit-wise loops for multiplies. fp-bit.c doesn't, it
uses actual multiply instructions, and hence may be faster.
I agree that fp-bit.c is slower than necessary, but it is folly to
assume that it is slower than all FP emulators. There are some that are
even slower, and lb1sf68.asm might be one.
> GMP isn't IEEE754 compatible, iirc. It's an arbitrary precision bignum
> library, and therefore unsuitable for as an fp-bit.c replacement.
You missed the point. This discussion is about how to do the 108-128
bit multiply that muldf3 needs. That is exactly what GMP was designed
for, and it will likely do it better than any hand written m68k code
will.
--
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com