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From: Andreas Schwab <schwab@suse.de>
To: Gabriel Paubert <paubert@iram.es>
Subject: Re: [PATCH 2/9] powerpc: Add macros to access floating
	point	registers in thread_struct.
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	<48626588.8050202@freescale.com> <20080625161255.GA12165@iram.es>
Date: Wed, 25 Jun 2008 19:08:00 +0200
In-Reply-To: <20080625161255.GA12165@iram.es> (Gabriel Paubert's message of
	"Wed, 25 Jun 2008 18:12:55 +0200")
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Cc: Scott Wood <scottwood@freescale.com>, linuxppc-dev@ozlabs.org,
	Michael Neuling <mikey@neuling.org>, Paul Mackerras <paulus@samba.org>
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Gabriel Paubert <paubert@iram.es> writes:

> On Wed, Jun 25, 2008 at 10:34:32AM -0500, Scott Wood wrote:
>> Kumar Gala wrote:
>> >>+/* Macros to workout the correct index for the FPR in the thread 
>> >>struct */
>> >>+#define FPRNUMBER(i) (((i) - PT_FPR0) >> 1)
>> >>+#define FPRHALF(i) (((i) - PT_FPR0) % 2)
>> >
>> >Have you looked at what the compiler spits out here to make sure we 
>> >aren't getting a divide?  Seems like we could use '& 0x1'.
>> 
>> GCC's not *that* dumb.  However, you may get some unnecessary 
>> sign-twiddling if "i" is signed.
>
> Not for modulo 2, it's only an even/odd choice

That's wrong.  -1 % 2 == -1, 1 % 2 == 1.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
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