From owner-svn-src-head@FreeBSD.ORG  Sat Aug 21 13:59:41 2010
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 7E57D1065693;
	Sat, 21 Aug 2010 13:59:41 +0000 (UTC)
	(envelope-from dimitry@andric.com)
Received: from tensor.andric.com (cl-327.ede-01.nl.sixxs.net
	[IPv6:2001:7b8:2ff:146::2])
	by mx1.freebsd.org (Postfix) with ESMTP id 4057D8FC12;
	Sat, 21 Aug 2010 13:59:41 +0000 (UTC)
Received: from [IPv6:2001:7b8:3a7:0:5bf:3b80:dc99:ff32] (unknown
	[IPv6:2001:7b8:3a7:0:5bf:3b80:dc99:ff32])
	(using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits))
	(No client certificate requested)
	by tensor.andric.com (Postfix) with ESMTPSA id 243425C59;
	Sat, 21 Aug 2010 15:59:40 +0200 (CEST)
Message-ID: <4C6FDBCF.6070101@andric.com>
Date: Sat, 21 Aug 2010 15:59:43 +0200
From: Dimitry Andric <dimitry@andric.com>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.2; en-US;
	rv:1.9.2.9pre) Gecko/20100814 Lanikai/3.1.3pre
MIME-Version: 1.0
To: Bruce Evans <brde@optusnet.com.au>
References: <201008191259.o7JCxv3i004613@svn.freebsd.org>
	<20100820075236.L18914@delplex.bde.org>
	<4C6DC0F8.9040001@andric.com>
	<20100821054033.M19850@delplex.bde.org>
In-Reply-To: <20100821054033.M19850@delplex.bde.org>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
	src-committers@FreeBSD.org, Rui Paulo <rpaulo@FreeBSD.org>
Subject: Re: svn commit: r211505 - head/contrib/gcc
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
	<svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 21 Aug 2010 13:59:41 -0000

On 2010-08-20 22:36, Bruce Evans wrote:
> On Fri, 20 Aug 2010, Dimitry Andric wrote:
[...] 
>> But will the casts not potentially hide problems, if you pass the wrong
>> types to those macros?  Maybe it is better if the compiler complains
>> that some argument is of an incompatible type, than just forcing it to
>> cast?
> This is unclear.  All integer types are compatible to some extent.
> Upcasting them always works and downcasting them works iff the value
> is not changed.

I meant this in the context of this llvm PR, about matching inline asm
input constraints with output constraints of an incompatible type:

  http://llvm.org/bugs/show_bug.cgi?id=3373

Clang is currently somewhat pickier about the arguments to inline asm,
which we also noticed in OpenSSL code, where a rotate-left macro is
defined (for i386 and amd64) as:

#   define ROTATE(a,n)	({ register unsigned int ret;	\
				  asm (			\
				  "roll %1,%0"		\
				  : "=r"(ret)		\
				  : "I"(n), "0"(a)	\
				  : "cc");		\
			     ret;			\
			  })

On amd64, it was being called with the 'a' argument being of unsigned
long type.  Clang complained:

crypto/openssl/crypto/md4/md4_dgst.c:117:2:
error: unsupported inline asm: input with type 'unsigned long' matching
output with type 'unsigned int'
	  R0(A,B,C,D,X( 0), 3,0); HOST_c2l(data,l); X( 2)=l;
	  ^~~~~~~~~~~~~~~~~~~~~~

In this case, the OpenSSL developers chose to explicitly cast 'a' to
'unsigned int' (see <http://cvs.openssl.org/chngview?cn=19818>).