linux-kernel - Re: ARM assembly syntax (was Re: [patch 03/36] Hexagon: Add bitops support)

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Message-ID: <20110902165345.GA27018@atrey.karlin.mff.cuni.cz>
Date:	Fri, 2 Sep 2011 18:53:45 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Linas Vepstas (Code Aurora)" <linas@...eaurora.org>
Cc:	Richard Kuo <rkuo@...eaurora.org>, linux-kernel@...r.kernel.org,
	linux-hexagon@...r.kernel.org
Subject: Re: ARM assembly syntax  (was Re: [patch 03/36] Hexagon: Add
	bitops support)

> On Fri, Aug 26, 2011 at 10:34:10PM +0200, Pavel Machek wrote:
> > Hi!
> > 
> > > +	__asm__ __volatile__ (
> > > +	"	{R10 = %1; R11 = asr(%2,#5); }\n"
> > > +	"	{R10 += asl(R11,#2); R11 = and(%2,#0x1f)}\n"
> > > +	"1:	R12 = memw_locked(R10);\n"
> > > +	"	{ P0 = tstbit(R12,R11); R12 = clrbit(R12,R11); }\n"
> > > +	"	memw_locked(R10,P1) = R12;\n"
> > > +	"	{if !P1 jump 1b; %0 = mux(P0,#1,#0);}\n"
> > 
> > Nice assembly syntax, btw. I can only wish architectures such as arm
> > used something as readable...
> 
> Yes, I, too, was very pleasantly surprised when I first saw this.

> Of course, one *could* alter binutils to accept something similar
> for ARM, and then alter gcc to spit it out. Whether anyone would use

Well, it would be enough if binutils accepted this; making gcc
generate it is optional. It would be mostly used for inline assembly etc...

> this isn't clear .. and I can already almost hear certain maintainers
> telling us how much of a bad idea this is from the maintainership
> point-of-view ....

Well, on x86, we already have at&t and intel assembly syntax. Having
one that was readable would be bonus :-).

[I don't expect anyone to _write_ assembly for unknown processor; but
being able to _read_ unfamiliar assembly would be already huge step
forward.]

And yes, I did notice it is VLIW. Those {} make it pretty obvious.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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