From: David Miller <davem@davemloft.net>
To: rth@redhat.com
Cc: gcc@gcc.gnu.org
Subject: Re: VIS2 pattern review
Date: Thu, 13 Oct 2011 20:06:00 -0000 [thread overview]
Message-ID: <20111013.143528.1318292403050799329.davem@davemloft.net> (raw)
In-Reply-To: <20111013.142636.1859659747859622111.davem@davemloft.net>
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.
next prev parent reply other threads:[~2011-10-13 18:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-13 12:29 Richard Henderson
2011-10-13 19:56 ` David Miller
2011-10-13 20:06 ` David Miller [this message]
2011-10-13 20:20 ` Richard Henderson
2011-10-13 22:46 ` David Miller
2011-10-13 22:53 ` Richard Henderson
2011-10-14 1:50 ` David Miller
2011-10-14 4:38 ` Eric Botcazou
2011-10-14 6:06 ` David Miller
2011-10-14 16:40 ` Eric Botcazou
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