From: Steve Ellcey <sellcey@marvell.com>
To: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
"James.Greenhalgh@arm.com" <James.Greenhalgh@arm.com>,
"Richard.Earnshaw@arm.com" <Richard.Earnshaw@arm.com>,
"Wilco.Dijkstra@arm.com" <Wilco.Dijkstra@arm.com>,
"Richard.Sandiford@arm.com" <Richard.Sandiford@arm.com>,
"Ramana.Radhakrishnan@arm.com"
<Ramana.Radhakrishnan@arm.com>
Cc: "nd@arm.com" <nd@arm.com>
Subject: Re: [PATCH][AArch64] Increase default function alignment
Date: Fri, 31 May 2019 15:48:00 -0000 [thread overview]
Message-ID: <b9014c972a817672536da624b18c6f2e8294d56c.camel@marvell.com> (raw)
In-Reply-To: <VI1PR0801MB21279519E21E8E2AEED6C6B883190@VI1PR0801MB2127.eurprd08.prod.outlook.com>
On Fri, 2019-05-31 at 11:52 +0000, Wilco Dijkstra wrote:
> With -mcpu=generic the function alignment is currently 8, however almost all
> supported cores prefer 16 or higher, so increase the default to 16:12.
> This gives ~0.2% performance increase on SPECINT2017, while codesize is 0.12%
> larger.
>
> ChangeLog:
> 2019-05-31 Wilco Dijkstra <wdijkstr@arm.com>
>
> * config/aarch64/aarch64.c (generic_tunings): Set function
> alignment to 16.
>
> --
>
> diff --git a/gcc/config/aarch64/aarch64.c
> b/gcc/config/aarch64/aarch64.c
> index
> 0023cb37bbae5afe9387840c1bb6b43586d4fac2..ed1422af6aab5e3c6eeea37ec57
> e69b64092a0ab 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -693,7 +693,7 @@ static const struct tune_params generic_tunings =
> 4, /* memmov_cost */
> 2, /* issue_rate */
> (AARCH64_FUSE_AES_AESMC), /* fusible_ops */
> - "8", /* function_align. */
> + "16:12", /* function_align. */
> "4", /* jump_align. */
> "8", /* loop_align. */
> 2, /* int_reassoc_width. */
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.
Steve Ellcey
sellcey@marvell.com
next prev parent reply other threads:[~2019-05-31 15:28 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 [this message]
2019-05-31 16:12 ` Wilco Dijkstra
2019-07-31 17:00 ` Wilco Dijkstra
2019-08-12 18:43 ` James Greenhalgh
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