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Date: Sun, 5 Nov 2017 15:01:08 -0600 From: Josh Poimboeuf <jpoimboe@...hat.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Ingo Molnar <mingo@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [GIT PULL] core kernel fixes On Sun, Nov 05, 2017 at 12:12:31PM -0800, Linus Torvalds wrote: > On Sun, Nov 5, 2017 at 11:53 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote: > > > > The GCC manual says: > > > > "asm statements that have no output operands, including asm goto > > statements, are implicitly volatile." > > Hmm. Fair enough. > > And the manual does say that it can merge and duplicate those asms > (and suggests using "%=" to generate a unique number, but I guess > "%c0" with __COUNTER__ is equivalent). > > I think the gcc manual has changed. I'm pretty certain it used to say > that "volatile" asms would not be "moved significantly". They've > silently changed semantics before too, oh well. I had tried the '%=' thing before, because that was exactly what I needed. But alas, it's not supported by the older GCCs. -- Josh
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