From: Jason Gunthorpe <jgg@nvidia.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
maz@kernel.org, will@kernel.org
Subject: Re: [PATCH] arm64: io: permit offset addressing
Date: Wed, 24 Jan 2024 13:24:18 -0400 [thread overview]
Message-ID: <20240124172418.GI1455070@nvidia.com> (raw)
In-Reply-To: <20240124111259.874975-1-mark.rutland@arm.com>
On Wed, Jan 24, 2024 at 11:12:59AM +0000, Mark Rutland wrote:
> Currently our IO accessors all use register addressing without offsets,
> but we could safely use offset addressing (without writeback) to
> simplify and optimize the generated code.
> Aside from the better code generation, there should be no functional
> change as a result of this patch. I have lightly tested this patch,
> including booting under KVM (where some devices such as PL011 are
> emulated).
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
FWIW I have had 0-day compile test a very similar patch with no
compilation problems.
I also got similar code savings results.
However, I noticed that clang 17.0.6 at least does not have any
benifit, I suppose it is a missing compiler feature.
Finally, in my experiments with the WC issue it wasn't entirely
helpful, I could not get both gcc and clang always generate load-free
store sequences for 64 bytes even with this.
Jason
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next prev parent reply other threads:[~2024-01-24 17:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 11:12 [PATCH] arm64: io: permit offset addressing Mark Rutland
2024-01-24 17:24 ` Jason Gunthorpe [this message]
2024-01-25 11:22 ` Mark Rutland
2024-01-30 11:56 ` Will Deacon
2024-02-20 18:20 ` Catalin Marinas
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