From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: Select ARCH_HAS_FAST_MULTIPLIER
Date: Wed, 25 Apr 2018 14:41:20 +0100 [thread overview]
Message-ID: <20180425134119.GE8383@arm.com> (raw)
In-Reply-To: <877b532d8d240c1d9e9db923c84b924443a218ed.1524583390.git.robin.murphy@arm.com>
On Tue, Apr 24, 2018 at 04:25:47PM +0100, Robin Murphy wrote:
> It is probably safe to assume that all Armv8-A implementations have a
> multiplier whose efficiency is comparable or better than a sequence of
> three or so register-dependent arithmetic instructions. Select
> ARCH_HAS_FAST_MULTIPLIER to get ever-so-slightly nicer codegen in the
> few dusty old corners which care.
>
> In a contrived benchmark calling hweight64() in a loop, this does indeed
> turn out to be a small win overall, with no measurable impact on
> Cortex-A57 but about 5% performance improvement on Cortex-A53.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
Acked-by: Will Deacon <will.deacon@arm.com>
Will
next prev parent reply other threads:[~2018-04-25 13:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-24 15:25 [PATCH] arm64: Select ARCH_HAS_FAST_MULTIPLIER Robin Murphy
2018-04-25 13:41 ` Will Deacon [this message]
2018-05-16 10:51 ` Catalin Marinas
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