[Issue 5757] std.math: exp, expm1, exp2 return 'inf' when no asm.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=5757



--- Comment #3 from Iain Buclaw <ibuclaw at ubuntu.com> 2011-03-21 04:09:10 PDT ---
GDC somewhat a bit exceptional, as there's both library functions and it's own
internal real_t floating point emulation routines available (which is not
exactly IEEE 754 compliant, but is close to the description of characteristics
of floating types in the ISO C99 standard), etc...
And there's call optimisation and constant folding which means if the values
are known at compile-time, then most calls would have been evaluated away. (ie:
logN(expN(x))  =>  x)

And I'm sure both GCC and libc aren't always quite what the DMD unittests
expect anyway. I know of at least 1 'off-by-one' math unittest that fails
because of GCC backend truncates rather than rounds the value from real to
double, and another where 1.5 * 10 makes 15.0000000001 - or something to that
effect when formatted into a string literal.

In any case, I'm more concerned about not hurting the systems that *do* have
80-bit math functions. The only other systems out there I can think of that
have it is IA64 - which I have no hardware (though David's already mentioned
that there's yet no IASM for for 64bit on GDC anyway. :)

Regards

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