Don wrote:
I'm not even sure how that should work. On x86, there are two completely
independent FPU rounding modes and exception masks: one for x87, and one
for SSE. Additionally, some of these may have rounding modes which
aren't support by the others (almost all CPUs other than x87 have a
flush-subnormals-to-zero mode; and in the IEEE spec, decimal floating
point has two extra rounding modes that binary doesn't have).
What this means, I think, is that the D-supplied mechanism for
controlling rounding mode and exceptions needs to be general enough to
support them all.
The D functions to get/set the modes should set both of them to the same
value. Exception flag readers should OR the two together. This is
because the compiler/library will likely mix & match using the SSE and
x87 as convenient.
Unsupported modes should throw an exception on attempting to set them.
