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RE: [patch] Improve loop array prefetch for IA-64
- From: "Davis, Mark" <mark dot davis at intel dot com>
- To: "Canqun Yang" <canqun at yahoo dot com dot cn>, <gcc at gcc dot gnu dot org>, <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 2 Jun 2006 11:21:20 -0400
- Subject: RE: [patch] Improve loop array prefetch for IA-64
Nice job getting this ready for the current version of gcc!
Question: does gcc now know the difference between prefetching to cache L1 via "lfetch", as opposed to prefetching only to level L2 via "lfetch.nt1"? For floating point data, the latter is the only interesting case because float loads only access the L2. Thus using "lfetch" for floating point arrays will unnecessarily wipe out the contents of L1. (gcc 3.2.3 only seems to generate "lfetch", which is why I ask...)
From: Canqun Yang [mailto:firstname.lastname@example.org]
Sent: Friday, June 02, 2006 5:14 AM
To: email@example.com; firstname.lastname@example.org
Subject: [patch] Improve loop array prefetch for IA-64
This patch results a performance increase of 4% for SPECfp2000 and 13% for NAS benchmark suite on
Itanium-2 system, respectively. More performance increase is hopeful by further tuning the
parameters and improving the prefetch algorithm at tree level.