Re: [Qemu-devel] [PATCH] target-i386/FPU: wrong conversion infinity from float80 to int32/int64

[Peter Maydell]

On 23 July 2014 12:55, Dmitry Poletaev <address@hidden> wrote:
> 14.07.2014, 18:59, "Peter Maydell" <address@hidden>:
>
>>  Since softfloat's status flags are sticky ...
>
> What does it mean?

"Sticky" here means that the status flags accumulate the
status from a sequence of operations: a softfloat function
will set the flag if the relevant exception occurred, but if
the exceptional condition did not happen then the flag will
be left at whatever its preceding value was. So you can't
just say "if the flag is set then the last operation I did set
it", because it might have been set by some operation
before that. (That is, once a bit gets set in the flags word
it "sticks" and doesn't go away.)

This matches the IEEE mandated behaviour for
floating point exception flags, which is why we do it.

thanks
-- PMM