Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobberedunnecessarily

From: Linus Torvalds
Date: Tue Jul 24 2007 - 17:47:20 EST




On Tue, 24 Jul 2007, Jeremy Fitzhardinge wrote:
> >
> > But gcc docs also talk about the other things volatile means, including
> > "not significantly moved".
>
> Actually, it doesn't. In fact it goes out of its way to say that "asm
> volatile" statements can be moved quite a bit, with respect to other
> asms, other code, jumps, basic blocks, etc.

Ahh. That's newer.

Historically, gcc manuals used to say "may not be deleted or significantly
reordered".

So they've weakened what it means, probably exactly because it wasn't
well-defined before either.

Linus
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