From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
jsrhbz@kanargh.force9.co.uk,
christoph.muellner@theobroma-systems.com, linux@roeck-us.net,
linux@rasmusvillemoes.dk, paulmck@linux.vnet.ibm.com,
tglx@linutronix.de, akpm@linux-foundation.org,
maxime.coquelin@st.com, linux-kernel@vger.kernel.org,
martink@posteo.de, tytso@mit.edu,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:core/types] bitops: Add sign_extend8(), 16 and 64 functions
Date: Thu, 05 Feb 2015 08:39:19 -0800 [thread overview]
Message-ID: <54D39CB7.6080504@zytor.com> (raw)
In-Reply-To: <20150205071734.GA3203@gmail.com>
On 02/04/2015 11:17 PM, Ingo Molnar wrote:
>>>
>>> Even for the 8bit ones? Since we have the *H and *L register
>>> we have more 8 bit regs than we have 16/32 bit regs and it
>>> might just be worth it.
>>
>> Fewer, actually. gcc doesn't really use the H registers much,
>
> Is that true for other compilers as well?
>
Probably. It wrecks havoc on register allocation, and it doesn't buy
that much, especially on 64 bits where all the registers can be used for
8-bit operations.
-hpa
prev parent reply other threads:[~2015-02-05 16:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-12 17:22 [PATCH v2] bitops.h: add sign_extend8(), 16 and 64 functions Martin Kepplinger
2015-01-12 17:28 ` [RFC] input: gtco: use bitops' sign_extend8 Martin Kepplinger
2015-01-12 17:28 ` [RFC] rtc: use sign_extend8 instead of manual conversion Martin Kepplinger
2015-01-12 17:28 ` [RFC] media: stb0899: use sign_extend8 instead of manual work Martin Kepplinger
2015-01-12 17:28 ` [RFC] hwmon: jc42: use bitops' sign_extend16 Martin Kepplinger
2015-01-12 19:53 ` Guenter Roeck
2015-01-12 19:48 ` [PATCH v2] bitops.h: add sign_extend8(), 16 and 64 functions Guenter Roeck
2015-01-14 16:56 ` [RFC PATCH 0/4] Example changes using proposed sign_extend functions Martin Kepplinger
2015-01-14 16:56 ` [PATCH 1/4] input: gtco: use bitops' sign_extend8 Martin Kepplinger
2015-01-14 16:56 ` [PATCH 2/4] rtc: use sign_extend8 instead of manual conversion Martin Kepplinger
2015-01-14 16:56 ` [PATCH 3/4] media: stb0899: use sign_extend8 instead of manual work Martin Kepplinger
2015-01-14 16:56 ` [PATCH 4/4] hwmon: jc42: use bitops' sign_extend16 Martin Kepplinger
2015-01-18 19:06 ` [tip:core/types] bitops: Add sign_extend8(), 16 and 64 functions tip-bot for Martin Kepplinger
[not found] ` <CA+55aFyc7TbnLBi3rcQDrtkwg9TgDnb5dAfupMGSbTKZC6Xd0g@mail.gmail.com>
2015-01-19 1:11 ` Guenter Roeck
2015-01-19 4:00 ` Linus Torvalds
2015-01-20 12:30 ` [PATCH v3 0/2] bitops.h: add sign_extend64() API and improve doc Martin Kepplinger
2015-01-20 12:30 ` [PATCH 1/2] bitops.h: improve documentation for sign_extend32() Martin Kepplinger
2015-01-20 12:30 ` [PATCH 2/2] bitops.h: Add sign_extend64() API Martin Kepplinger
2015-01-19 10:04 ` [tip:core/types] bitops: Add sign_extend8(), 16 and 64 functions Peter Zijlstra
2015-01-21 20:22 ` H. Peter Anvin
2015-02-05 7:17 ` Ingo Molnar
2015-02-05 14:11 ` Guenter Roeck
2015-02-12 11:11 ` Example use of sign_extend64() Martin Kepplinger
2015-02-12 11:11 ` [RFC][PATCH] arch: sh: use sign_extend64() for sign extension Martin Kepplinger
2015-02-05 16:39 ` H. Peter Anvin [this message]
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