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Date: Tue, 06 Apr 2010 16:37:00 -0000
From: Jim Wilson <wilson@codesourcery.com>
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To: roy rosen <roy.1rosen@gmail.com>
CC: gcc@gcc.gnu.org
Subject: Re: lower subreg optimization
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On 04/06/2010 02:24 AM, roy rosen wrote:
> (insn 33 32 34 7 a.c:25 (set (subreg:V2HI (reg:V4HI 114) 0)
>          (plus:V2HI (subreg:V2HI (reg:V4HI 112) 0)
>              (subreg:V2HI (reg:V4HI 113) 0))) 118 {addv2hi3} (nil))

Only subregs are decomposed.  So use vec_select instead of subreg.  I 
see you already have a vec_concat to combine the two v2hi into one v4hi, 
so there is no need for the subreg in the dest.  You should try 
eliminating that first and see if that helps.  If that isn't enough, 
then replace the subregs in the source with vec_select operations.

Jim