From: ebiederm@xmission.com (Eric W. Biederman)
To: Andi Kleen <ak@suse.de>
Cc: vgoyal@in.ibm.com,
       linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Reloc Kernel List <fastboot@lists.osdl.org>, akpm@osdl.org,
       hpa@zytor.com, magnus.damm@gmail.com, lwang@redhat.com,
       dzickus@redhat.com
Subject: Re: [RFC] [PATCH 2/16] x86_64: Assembly safe page.h and pgtable.h
References: <20061113162135.GA17429@in.ibm.com>
	<200611131817.01066.ak@suse.de> <20061113211636.GC13832@in.ibm.com>
	<200611140246.28433.ak@suse.de>
Date: Mon, 13 Nov 2006 19:41:17 -0700
In-Reply-To: <200611140246.28433.ak@suse.de> (Andi Kleen's message of "Tue, 14
	Nov 2006 02:46:28 +0100")
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Andi Kleen <ak@suse.de> writes:

>> 
>> I think we need these UL suffixes. Otherwise in some cases overflow
>> can take place and compiler emits warning.
>> 
>> For ex. in following definition I got rid of UL.
>> 
>> #define PGDIR_SIZE      (1 << PGDIR_SHIFT) 
>
> Yes for the shifts it is needed, but not for the unshifted constants.
> I think. At least when they're hex the compiler should chose the right
> type on its own.

Only if the high bit is set.  But it should chose a big enough type.
However there is no reason to play games and possibly out smart ourselves.
That is the point of the _AC() macro.  It adds the suffix only for
C code, and drops it for assembly.

Eric
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