On Tuesday, 26 August 2014 at 07:34:05 UTC, Ola Fosheim Gr wrote:
On Tuesday, 26 August 2014 at 07:24:19 UTC, Don wrote:
Processors from AMD have signalling NaN behaviour which is
different from processors from Intel.
And the situation is worst on most other architectures. It's a
lost cause, I think.
I disagree. AFAIK signaling NaN was standardized in IEEE
754-2008.
So it receives attention.
It was always in IEEE754. The decision in 754-2008 was simply to
not remove it from the spec (a lot of people wanted to remove
it). I don't think anything has changed.
The point is, existing hardware does not support it consistently.
It's not possible at reasonable cost.
---
real uninitialized_var = real.snan;
void foo()
{
real other_var = void;
asm {
fld uninitialized_var;
fstp other_var;
}
}
---
will signal on AMD, but not Intel. I'd love for this to work, but
the hardware is fighting against us. I think it's useful only for
debugging.
