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From: Lukas Wunner <lukas@wunner.de>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Puranjay Mohan <puranjay12@gmail.com>, linux-pci@vger.kernel.org
Subject: Re: [PATCH 1/2] PCI: Update BAR # and window messages
Date: Wed, 24 Nov 2021 05:28:10 +0100	[thread overview]
Message-ID: <20211124042810.GB1887@wunner.de> (raw)
In-Reply-To: <20211119214304.GA1963177@bhelgaas>

On Fri, Nov 19, 2021 at 03:43:04PM -0600, Bjorn Helgaas wrote:
> On Sat, Nov 06, 2021 at 12:58:31PM +0100, Lukas Wunner wrote:
> > Use a static const array of char * instead of a switch/case ladder
> > to reduce LoC count and improve performance.
> 
> I tried converting this and came up with the below.  Is that the sort
> of thing you're thinking?  Gcc *does* generate slightly smaller code
> for it, but Puranjay's original source code is smaller and IMO a
> little easier to read.

Yes, that's what I had in mind.  Aside from binary or source code size,
retrieving the name from an array is just a quick direct access, whereas
a switch/case ladder becomes a lot of conditional branches in binary code,
which is slower.

Another option is to use case ranges.  See max3191x_set_config() in
drivers/gpio/gpio-max3191x.c for an example.  gcc is smart enough to
generate an optimized set of conditional greater-than / less-than branches.
That could be used to shorten your cardbus_name[] array.

Thanks,

Lukas

  reply	other threads:[~2021-11-24  4:28 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-06 11:26 [PATCH 0/2] PCI: Update BAR #/window messages Puranjay Mohan
2021-11-06 11:26 ` [PATCH 1/2] PCI: Update BAR # and window messages Puranjay Mohan
2021-11-06 11:58   ` Lukas Wunner
2021-11-19 21:43     ` Bjorn Helgaas
2021-11-24  4:28       ` Lukas Wunner [this message]
2021-11-06 11:26 ` [PATCH 2/2] PCI: Use resource names in PCI log messages Puranjay Mohan

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