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From: Richard Henderson <rth@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Uros Bizjak <ubizjak@gmail.com>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Optimize (x * 8) | 5 and (x << 3) ^ 3 to use lea (PR target/48688)
Date: Wed, 20 Apr 2011 17:51:00 -0000	[thread overview]
Message-ID: <4DAF1788.7060306@redhat.com> (raw)
In-Reply-To: <20110420160959.GR17079@tyan-ft48-01.lab.bos.redhat.com>

On 04/20/2011 09:09 AM, Jakub Jelinek wrote:
> Hi!
> 
> This splitter allows us to optimize (x {* {2,4,8},<< {1,2,3}}) {|,^} y
> for constant integer y <= {1ULL,3ULL,7ULL} using lea{l,q} (| or ^ in
> that case, when the low bits are known to be all 0, is like plus).
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> 
> 2011-04-20  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR target/48688
> 	* config/i386/i386.md (*lea_general_4): New define_insn_and_split.

Any chance you could do this in combine instead?  Shift-and-add patterns
are a fairly common architectural feature...


r~

  reply	other threads:[~2011-04-20 17:27 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-20 16:36 Jakub Jelinek
2011-04-20 17:51 ` Richard Henderson [this message]
2011-04-21 13:01   ` Jakub Jelinek
2011-06-04 15:20 ` H.J. Lu
2011-06-04 15:40   ` Jakub Jelinek

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