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Re: Floating Point Representation in libgcc (is IEEE?)
On Tue, Jun 15, 2010 at 2:13 PM, Joern Rennecke <amylaar@spamcop.net> wrote:
>
> It is using whatever floating point format the target has.
> If you don't have hardware floating point support, then you get to
> choose the format when you design your ABI.
Yes, my target has no fp.
Thanks! This is not mine to decide if I just use a gcc floating point
library like fp-bit and soft-fp, right?
> There are two C implementations of IEEE software floating point in the
> GCC runtime:
> - fp-bit.c, which is fairly old and slow, but requires little work to use
> Âif longlong.h supports your processor (which is also needed for GNU mp).
> ÂIt only has round-to-nearest, no signals, but subnormals work except for
> Âone rounding issue with division.
> - soft-fp. ÂThis is supposed to be a bit faster, but you need to define
> Âvarious primitives. ÂThe default configuration is similar in features
> Âto fp-bit.c, but you can customize it for support of signals ('exceptions')
> Âand other rounding modes.
>
I started using fp-bit.c since I read somewhere (I wonder where I read
this) that soft-fp won't work if BITS_PER_UNIT != 8.
Is there any documentation explaining the implementation of floating
points in fp-bit.c and soft-fp.c? Mainly their internal
representation.
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