Re: GCC memory barriers are missing "cc" clobbers

On 2014-09-19 09:58:01 -0400, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.com> writes:
> > On 2014-09-19 12:00:16 +0200, Andres Freund wrote:
> >> But addl sets condition flags. So this really also needs a "cc" clobber?
> >> Or am I missing something?
> 
> > What I missed is that x86 has an implied "cc" clobber for every inline
> > assembly statement. So forget that.
> 
> While it might not be buggy as it stands, I think we should add the "cc"
> rather than rely on it being implicit.  One reason is that people will
> look at the x86 cases when developing code for other architectures, and
> they could easily forget to add "cc" on machines where it does matter.

Fair point. It's also extremly poorly documented - my answer is from a
gcc dev, I haven't found an official document stating it. I don't really
see any need to backpatch though, do you?

Andres Freund

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