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Re: PROPOSAL: Extend inline asm syntax with size spec
- From: Borislav Petkov <bp at alien8 dot de>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>, Ingo Molnar <mingo at kernel dot org>
- Cc: Richard Biener <rguenther at suse dot de>, Michael Matz <matz at suse dot de>, gcc at gcc dot gnu dot org, Nadav Amit <namit at vmware dot com>, Ingo Molnar <mingo at redhat dot com>, linux-kernel at vger dot kernel dot org, x86 at kernel dot org, Masahiro Yamada <yamada dot masahiro at socionext dot com>, Sam Ravnborg <sam at ravnborg dot org>, Alok Kataria <akataria at vmware dot com>, Christopher Li <sparse at chrisli dot org>, Greg Kroah-Hartman <gregkh at linuxfoundation dot org>, "H. Peter Anvin" <hpa at zytor dot com>, Jan Beulich <JBeulich at suse dot com>, Josh Poimboeuf <jpoimboe at redhat dot com>, Juergen Gross <jgross at suse dot com>, Kate Stewart <kstewart at linuxfoundation dot org>, Kees Cook <keescook at chromium dot org>, linux-sparse at vger dot kernel dot org, Peter Zijlstra <peterz at infradead dot org>, Philippe Ombredanne <pombredanne at nexb dot com>, Thomas Gleixner <tglx at linutronix dot de>, virtualization at lists dot linux-foundation dot org, Linus Torvalds <torvalds at linux-foundation dot org>, Chris Zankel <chris at zankel dot net>, Max Filippov <jcmvbkbc at gmail dot com>, linux-xtensa at linux-xtensa dot org, Andrew Morton <akpm at linux-foundation dot org>
- Date: Wed, 10 Oct 2018 10:19:06 +0200
- Subject: Re: PROPOSAL: Extend inline asm syntax with size spec
- References: <20181003213100.189959-1-namit@vmware.com> <20181007091805.GA30687@zn.tnic> <20181007132228.GJ29268@gate.crashing.org> <alpine.LSU.2.21.1810071534220.7867@wotan.suse.de> <20181008073128.GL29268@gate.crashing.org> <alpine.LSU.2.20.1810081105350.16707@zhemvz.fhfr.qr> <20181009145330.GT29268@gate.crashing.org> <alpine.LSU.2.20.1810100909140.16707@zhemvz.fhfr.qr> <20181010072240.GB103159@gmail.com> <20181010080324.GV29268@gate.crashing.org>
On Wed, Oct 10, 2018 at 03:03:25AM -0500, Segher Boessenkool wrote:
> The code immediately after this makes it size 1, even for things like
> asm(""), I suppose this works better for the inliner. But that's a detail
> (and it might change); the description says "consider this asm as minimum
> length and cost for inlining decisions", which works for either 0 or 1.
Thanks for implementing this, much appreciated. If you need people to
test stuff, lemme know.
> You can think of it as meaning "we want this asm inlined always", and then
> whether that actually happens depends on if the function around it is
> inlined or not.
My only concern is how we would catch the other extremity where the
inline asm grows too big and we end up inlining it everywhere and thus
getting fat. The 0day bot already builds tinyconfigs but we should be
looking at vmlinux size growth too.
Thx.
--
Regards/Gruss,
Boris.
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