From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-return-170653-listarch-gcc=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 24116 invoked by alias); 13 Oct 2011 18:35:47 -0000
Received: (qmail 23841 invoked by uid 22791); 13 Oct 2011 18:35:45 -0000
X-SWARE-Spam-Status: No, hits=-1.8 required=5.0	tests=AWL,BAYES_00
X-Spam-Check-By: sourceware.org
Received: from shards.monkeyblade.net (HELO shards.monkeyblade.net) (198.137.202.13)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 13 Oct 2011 18:35:31 +0000
Received: from localhost (nat-pool-rdu.redhat.com [66.187.233.202])	(authenticated bits=0)	by shards.monkeyblade.net (8.14.4/8.14.4) with ESMTP id p9DIZSeN014475	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO);	Thu, 13 Oct 2011 11:35:30 -0700
Date: Thu, 13 Oct 2011 20:06:00 -0000
Message-Id: <20111013.143528.1318292403050799329.davem@davemloft.net>
To: rth@redhat.com
Cc: gcc@gcc.gnu.org
Subject: Re: VIS2 pattern review
From: David Miller <davem@davemloft.net>
In-Reply-To: <20111013.142636.1859659747859622111.davem@davemloft.net>
References: <4E96358F.30405@redhat.com>	<20111013.142636.1859659747859622111.davem@davemloft.net>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc/>
List-Post: <mailto:gcc@gcc.gnu.org>
List-Help: <http://gcc.gnu.org/ml/>
Sender: gcc-owner@gcc.gnu.org
X-SW-Source: 2011-10/txt/msg00211.txt.bz2

From: David Miller <davem@davemloft.net>
Date: Thu, 13 Oct 2011 14:26:36 -0400 (EDT)

> 	product = src1 * src2;
> 
> 	scaled = (product & 0x00ffff00) >> 8;
> 	if (product & 0x80)
> 		scaled++;

In fact, all of the partitioned multiply instructions scale the result
by 8 bits with rounding towards positive infinity.

Therefore, we have to use an unspec for all of them.