[cfe-dev] RFC: Support x86 interrupt and exception handlers

[Joerg Sonnenberger via cfe-dev]

On Tue, Sep 22, 2015 at 09:37:42AM +0100, David Chisnall via cfe-dev wrote:
> On 22 Sep 2015, at 09:16, Hal Finkel via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> > 
> > Sure, but I imagine saving all 32 AVX registers plus the GPRs, etc. is in the same ballpark.
> 
> Slightly off-topic, but this is one thing that we’ve noticed on FreeBSD
> where LLVM causes some performance regressions.  We lazily switch x87
> / SSE state on context switch, so the context switch cost is reduced
> for programs that don’t use them.

When we measured it for NetBSD, even with GCC, there was almost no cost
saving from lazy FPU context switchin for most loads. It comes with a
significant complexity though. Just FYI.

Joerg