Re: [PATCH RFC 0/7] x86: convert ticketlocks to C and remove duplicatecode

[H. Peter Anvin]

On 06/22/2011 12:21 PM, Jeremy Fitzhardinge wrote:
> 
> A friend just pointed out that gcc has a "__sync_fetch_and_add()"
> intrinsic, which compiles to xadd when used in this context.  What's the
> general feeling about using these kinds of gcc features?
> 

In general they are good, IF:

a) they cover all versions of gcc we care about (or we have a fallback),
and
b) they have the right semantics.

Using gcc intrinsics can generate better code than we can in inline
assembly.

However, (b) is a killer since gcc doesn't have a way to generate our
lock prefix annotations, and so it isn't really useful here.

	-hpa
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