FP context switching on i386

Thomas Doerfler Thomas.Doerfler at embedded-brains.de
Sat Oct 3 10:35:23 UTC 2009


although I am not at all familiar with i386 ABI stuff, I would guess
that we have to save the context during a task switch, at least when it
was forced due to a interrupt (e.g. timer) event. In these cases there
is no function call involved for the function that uses the FP context.


Till Straumann schrieb:
> I thought the i386 sysv ABI said that FP registers
> are not preserved across function calls -- doesn't
> this mean that there is no need for saving/restoring
> the FP context ? Am I missing something ?
> I was thinking about what it takes to support SSE
> and I believe it may essentially come for free
> since XMM registers seem not to be callee saved
> either. Hard to find that information though since
> e.g.,
> http://www.sco.com/developers/devspecs/abi386-4.pdf
> doesn't mention SSE yet.
> -- Till
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