From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: Steve Ellcey <sellcey@marvell.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
James Greenhalgh <James.Greenhalgh@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>,
Richard Sandiford <Richard.Sandiford@arm.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>
Cc: nd <nd@arm.com>
Subject: Re: [PATCH][AArch64] Increase default function alignment
Date: Fri, 31 May 2019 16:12:00 -0000 [thread overview]
Message-ID: <VI1PR0801MB2127EBF944D1888A17E0C42283190@VI1PR0801MB2127.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <b9014c972a817672536da624b18c6f2e8294d56c.camel@marvell.com>
Hi Steve,
> I have no objection to the change but could the commit message and/or
> comments be expanded to explain the ':12' part of this value. I
> couldn't find an explanation for it in the code and I don't understand
> what it does.
See https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-falign-functions
Basically the 12 guarantees there are at least 12 useable bytes in the
16-byte aligned block. This significantly lowers the overhead of padding
compared to always forcing 16-byte alignment. The Neoverse N1 tuning
already uses this feature.
Wilco
next prev parent reply other threads:[~2019-05-31 16:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-31 12:28 Wilco Dijkstra
2019-05-31 15:48 ` Steve Ellcey
2019-05-31 16:12 ` Wilco Dijkstra [this message]
2019-07-31 17:00 ` Wilco Dijkstra
2019-08-12 18:43 ` James Greenhalgh
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