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From: David Laight <David.Laight@ACULAB.COM>
To: 'Joe Perches' <joe@perches.com>,
	Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Cc: Mark Brown <broonie@kernel.org>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Matti Vaittinen <mazziesaccount@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 01/12] regmap-irq: Convert bool bitfields to unsigned int
Date: Fri, 24 Jun 2022 14:28:55 +0000	[thread overview]
Message-ID: <b9da7e05ce96443cacc1df9b2672eb51@AcuMS.aculab.com> (raw)
In-Reply-To: <ca26910886a765dd7edc4815ef90bedbd0f99a95.camel@perches.com>

From: Joe Perches 
> Sent: 24 June 2022 14:45
...
> I'm trying to show that conversions of bool:1->unsigned int:1
> as being trivial are not so trivial after all.
> 
> It's fairly common to have code like:
> 
> 	[bool] foo.bar = some_value & SETTING;
> 
> where some value is tested for a mask/bit and a non-zero is true.
> 
> So conversions of foo.bar from bool:1 to unsigned int:1 are not
> wise unless all possible side effects are known.

I can never decide whether:
	bool_c = bool_a & bool_b;
can be compiled to a simple 'and' instruction, or requires a
load of instructions in case bool_a and/or bool_b has a non-zero
value without the bottom bit set.

All other C types are cpu register types - so you know what happens.
IMHO bool is an abomination and should not be used :-)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


  reply	other threads:[~2022-06-24 14:29 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-23 21:14 [PATCH v2 00/12] regmap-irq cleanups and refactoring Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 01/12] regmap-irq: Convert bool bitfields to unsigned int Aidan MacDonald
2022-06-23 21:26   ` Andy Shevchenko
2022-06-24 12:11     ` Mark Brown
2022-06-24 12:46       ` Joe Perches
2022-06-24 12:56         ` Mark Brown
2022-06-24 13:05         ` Aidan MacDonald
2022-06-24 13:45           ` Joe Perches
2022-06-24 14:28             ` David Laight [this message]
2022-06-24 14:31             ` Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 02/12] regmap-irq: Remove unused type_reg_stride field Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 03/12] regmap-irq: Cleanup sizeof(...) use in memory allocation Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 04/12] regmap-irq: Remove an unnecessary restriction on type_in_mask Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 05/12] regmap-irq: Remove inappropriate uses of regmap_irq_update_bits() Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 06/12] regmap-irq: Remove mask_writeonly and regmap_irq_update_bits() Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 07/12] regmap-irq: Refactor checks for status bulk read support Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 08/12] regmap-irq: Introduce config registers for irq types Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 09/12] regmap-irq: Deprecate type registers and virtual registers Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 10/12] regmap-irq: Fix inverted handling of unmask registers Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 11/12] regmap-irq: Add get_irq_reg() callback Aidan MacDonald
     [not found]   ` <CGME20220701163330eucas1p13456e7757d9d2bc8d0aa35c16f143590@eucas1p1.samsung.com>
2022-07-01 16:33     ` Marek Szyprowski
2022-07-03 11:06       ` Aidan MacDonald
2022-06-23 21:14 ` [PATCH v2 12/12] regmap-irq: Deprecate the not_fixed_stride flag Aidan MacDonald
2022-06-30 17:27 ` [PATCH v2 00/12] regmap-irq cleanups and refactoring Mark Brown

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