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

[Hal Finkel via cfe-dev]

----- Original Message -----
> From: "Joerg Sonnenberger via cfe-dev" <cfe-dev at lists.llvm.org>
> To: cfe-dev at lists.llvm.org
> Sent: Monday, September 21, 2015 3:56:25 PM
> Subject: Re: [cfe-dev] RFC: Support x86 interrupt and exception handlers
> 
> On Mon, Sep 21, 2015 at 01:45:41PM -0700, H.J. Lu via cfe-dev wrote:
> > The main purpose of x86 interrupt attribute is to allow programmers
> > to write x86 interrupt/exception handlers in C WITHOUT assembly
> > stubs to avoid extra branch from assembly stubs to C functions.
> 
> Let's take just this statement. Are you sure that the call/ret pair
> for
> such a stub has *any* significant impact on the interrupt latency?
> I'm quite doubtful of that. That's completely ignoring the fact that
> raw
> interrupt or exception latency is generally not an issue.

I agree that this is a highly-relevant question. Demonstrating the benefit here is important. I can certainly imagine that it might be the case that on embedded systems the latency here is more important. The other thing is that it might matter a lot more for syscall/trap overhead than for actual externally-sourced interrupts.

 -Hal

> 
> Joerg
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory