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Re: IRA costs tweaks, PR 56069

From: Jeff Law <law at redhat dot com>
To: Vladimir Makarov <vmakarov at redhat dot com>, Bernd Schmidt <bschmidt at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
Date: Tue, 26 Apr 2016 21:56:57 -0600
Subject: Re: IRA costs tweaks, PR 56069
Authentication-results: sourceware.org; auth=none
References: <56D71977 dot 5040204 at t-online dot de> <56D72316 dot 2060207 at redhat dot com> <56D760CF dot 4030308 at redhat dot com>

On 03/02/2016 02:53 PM, Vladimir Makarov wrote:


The overall effect of this patch seems to be fairly minimal in
practice, which is slightly disappointing. On the whole, it seems to
be a very slight net positive, with few instances where we generate
additional instructions.

I am just speculating may be the most important thing for performance is
updating costs not their exact values (although the values can be
important in some cases too).

I suspect you're right -- when I was looking at handling reload viasplitting and calling back into IRA, cost updates were key to gettinggood code for the newly created pseudos. It wasn't a matter of gettingthem perfect, but a matter of getting them "reasonable".


jeff

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