On Fri, Mar 02, 2007 at 05:36:01PM -0800, Nicholas Miell wrote:
> > as an asynchronous context helps alot: the classic gcc convention for
> > FPU use & function calls should apply: gcc does not call an external
> > function with an in-use FPU stack/register, it always neatly unuses it,
> > as no FPU register is callee-saved, all are caller-saved.
>
> The i386 psABI is ancient (i.e. it predates SSE, so no mention of the
> XMM or MXCSR registers) and a bit vague (no mention at all of the FP
> status word), but I'm fairly certain that Ingo is right.
The FPU status word *must* be saved, as the rounding behaviour and error mode
bits are assumed to be preserved. Iow, yes, there is state which is required.
-ben
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