On 12/10/2010 15:17, Daniel Fischer wrote:
On Tuesday 12 October 2010 11:18:39, Simon Marlow wrote:
On 09/10/2010 10:07, Daniel Fischer wrote:
On Saturday 09 October 2010 06:34:32, Lennart Augustsson wrote:
That code is incorrect. You can't assume that the base for floating point numbers is 2, that's something you have to check. (POWER6 and z9 has hardware support for base 10 floating point.)
-- We assume that FLT_RADIX is 2 so that we can use more efficient code #if FLT_RADIX != 2 #error FLT_RADIX must be 2 #endif
Making the assumption is fine (as we do in the code above), but the important thing is to make the build fail in a very noisy way if the assumption turns out to be wrong (as above).
Cheers, Simon
Are there any other places where FLT_RADIX == 2 is assumed? (grepping the .hs, .lhs and .h files in the source tree for FLT_RADIX revealed nothing else.) If that's the only place where e.g. base 10 floating point would fail, we should make it work for that too. If on the other hand base 2 is assumed in other places, for primops, whatever, and that assumption is not going to be changed, I'd prefer not to litter the source with dead code.
I think the code in rts/StgPrimFloat.c assumes a lot about floating point representations. Cheers, Simon