From: Thomas Gleixner <tglx@linutronix.de>
To: huangshaobo3@xiaomi.com
Cc: bhelgaas@google.com, chenwei29@xiaomi.com, darwi@linutronix.de,
huangshaobo3@xiaomi.com, jgg@ziepe.ca, kevin.tian@intel.com,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
weipengliang@xiaomi.com, wengjinfei@xiaomi.com
Subject: Re: Subject: [PATCH] pci/msi: remove redundant calculation in msi_setup_msi_desc
Date: Thu, 24 Aug 2023 11:04:16 +0200 [thread overview]
Message-ID: <87o7iwdd67.ffs@tglx> (raw)
In-Reply-To: <1692862032-37839-1-git-send-email-huangshaobo3@xiaomi.com>
On Thu, Aug 24 2023 at 00:27, huangshaobo3@xiaomi.com wrote:
> On Wed, 23 Aug 2023 16:15:27 +0200, Thomas Gleixner wrote:
>> I'm not seeing what this solves:
>
>> > - if (control & PCI_MSI_FLAGS_64BIT)
>> > + if (desc.pci.msi_attrib.is_64)
>
>> Both variants resolve to a test of a bit and a conditional instruction
>> on the result. It's exactly zero difference in terms of "calculation".
>
>> So all this does is change the memory location to test. Not more not
>> less. It does not generate better code and does not save anything.
>
> It may not be appropriate to write to eliminate duplicate calculations,
> can it be proposed again with clean code?
What's wrong with the existing code?
next prev parent reply other threads:[~2023-08-24 9:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-18 7:26 Subject: [PATCH] pci/msi: remove redundant calculation in msi_setup_msi_desc 黄少波
2023-08-18 8:30 ` Ilpo Järvinen
2023-08-23 14:15 ` Thomas Gleixner
2023-08-24 7:27 ` huangshaobo3
2023-08-24 9:04 ` Thomas Gleixner [this message]
2023-08-24 10:52 ` sparkhuang
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