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SubjectRe: 2.2.0 and egcs 1.1 was Re: Sorry, wrong gcc-version


On Sun, 25 Oct 1998, David S. Miller wrote:
>
> For example, everybody in the egcs camp just decided that clobbers
> and inputs must not overlap. Nobody told me why, and why they can't
> just be automatically converted to early-clobbers inside gcc.
>
> You're telling the compiler two different things which conflict.

Which has worked before (and was certainly the _only_ way to do it in
gcc-1.40 which I started with).

And which is something so obvious to the compiler that it really shouldn't
generate bad code, it should just do the obvious thing. It's not as if the
concept is ambiguous or anything like that.

If gcc internally doesn't want to handle the construct, then it should be
truly trivial to make gcc turn the clobber into a early-clobber, which
according to everybody _should_ work.

The reason I do not agree with the gcc people about having to use
early-clobbers is that gcc also has limits on how many register specifiers
you can use. At some point it was just seven, and I think somebody upped
it to ten.

And doing early-clobbers by hand overflows that very very quickly, because
it essentially means you have to double all your input specifiers.

Linus


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