[PATCH] Add support for coldcc to clang

[John McCall]

On Feb 20, 2013, at 7:49 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
> On Wed, Feb 20, 2013 at 06:30:53PM -0800, John McCall wrote:
>> On Feb 20, 2013, at 6:24 PM, Richard Smith <richard at metafoo.co.uk> wrote:
>>> On Wed, Feb 20, 2013 at 6:18 PM, John McCall <rjmccall at apple.com> wrote:
>>> On Feb 20, 2013, at 6:13 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
>>>> http://llvm-reviews.chandlerc.com/D443
>>> 
>>> Are you sure we actually *want* to expose this to users?
>>> 
>>> I would like to mark the UBSan runtime handler functions as __attribute__((coldcc)), and I think that would make sense for other sanitizers too.
>> 
>> Are we now willing to commit to a fixed ABI for coldcc?  I thought we hadn't been.
> 
> Implementing __attribute__((coldcc)) does not necessarily imply fixing
> the ABI, provided that we document the attribute as such.  It should
> be safe to use in compiler_rt once we modify its build system to use the
> just-built clang.

I agree that we could certainly expose a calling convention with zero
binary-compatibility guarantees.  I don't know if that would work for what
Richard wants, though.  Notably, you can't stick that sort of thing in a
library that you haven't rev-locked to the compiler.

John.