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From: "congh at google dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/56902] Fails to SLP with mismatched +/- and negatable constants
Date: Mon, 11 Nov 2013 18:44:00 -0000	[thread overview]
Message-ID: <bug-56902-4-KwVohCWbvL@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-56902-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56902

Cong Hou <congh at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |congh at google dot com

--- Comment #1 from Cong Hou <congh at google dot com> ---
I just made a patch which supports limited non-isomorphic operations
(operations on even/odd elements are still isomorphic) for SLP. Then the three
loops you listed can be vectorized using SLP by using new VEC_ADDSUB_EXPR or
VEC_SUBADD_EXPR. For x86, SSE3 provides ADDSUBPD/ADDSUBPS instructions which
can do the job, but I also emulated them for SSE (use mask to negate the
even/odd elements and then add).

I think we will need to support more general non-isomorphic operations, which
is more difficult and challenging. But I think the limited support in this
patch is also useful at this time.

I will send the patch later.


  reply	other threads:[~2013-11-11 18:44 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-10  9:46 [Bug tree-optimization/56902] New: " rguenth at gcc dot gnu.org
2013-11-11 18:44 ` congh at google dot com [this message]
2013-11-13 15:39 ` [Bug tree-optimization/56902] " rguenth at gcc dot gnu.org
2015-10-22 10:03 ` rguenth at gcc dot gnu.org

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