Re: Some more patches for GCC on NetBSD/VAX coming soon...

[Greg Stark <stark%mit.edu@localhost>]

On Fri, Apr 1, 2016 at 9:20 PM, Jake Hamby <jehamby420%me.com@localhost> wrote:
> The reason I'd like to see better support for compiling as G_float (you can do it now with "-mg", but all of the libraries that you link with will crash or return bad results for any "double" values that you pass or receive, because the bits are interpreted differently) is that VAX floating point also does not support denormalized numbers, which means that there's an abrupt gap between +/-2.9e-39 and 0 (there's a hidden 1 bit, even when the mantissa is all 0). With IEEE math, there's special support for this case (see https://en.wikipedia.org/wiki/Denormal_number), which VAX doesn't support at all in any mode.


It would also be really handy to have -msoft-float support with IEEE
floating point implemented in software. This might also necessitate
some libc function variants compiled with -msoft-float being
available.

A big part of the reason to have a VAX port at all is to have a
non-IEEE fp platform to test on. But the problem is that while we want
to be sure our internal code doesn't depend on IEEE fp we can't really
run our regression tests on VAX at all because there are so many
user-visible floating point operations in the tests that all fail. I
would love to compile just the user visible float data type using
soft-math and use D_FLOAT or G_FLOAT for all the internal floating
point arithmetic.


-- 
greg