From: Blue Swirl <blauwirbel@gmail.com>
To: Richard Henderson <rth@twiddle.net>
Cc: mj.mccormack@samsung.com, qemu-devel@nongnu.org, zhur@ispras.ru,
Kirill Batuzov <batuzovk@ispras.ru>
Subject: Re: [Qemu-devel] [PATCH 5/6] Do constant folding for shift operations.
Date: Fri, 27 May 2011 20:07:01 +0300 [thread overview]
Message-ID: <BANLkTinHp7fwCh0jLHR5z0tHLdptQ8sUUw@mail.gmail.com> (raw)
In-Reply-To: <4DDEC29D.6020204@twiddle.net>
On Fri, May 27, 2011 at 12:14 AM, Richard Henderson <rth@twiddle.net> wrote:
> On 05/26/2011 01:25 PM, Blue Swirl wrote:
>>> I don't see the point. The C99 implementation defined escape hatch
>>> exists for weird cpus. Which we won't be supporting as a QEMU host.
>>
>> Maybe not, but a compiler with this property could arrive. For
>> example, GCC developers could decide that since this weirdness is
>> allowed by the standard, it may be implemented as well.
>
> If you like, you can write a configure test for it. But, honestly,
> essentially every place in qemu that uses shifts on signed types
> would have to be audited. Really.
OK.
> The C99 hook exists to efficiently support targets that don't have
> arithmetic shift operations. Honestly.
So it would be impossible for a compiler developer to change the logic
for shifts for some supported two's-complement logic CPUs (like x86)
just because it's legal?
next prev parent reply other threads:[~2011-05-27 17:07 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-20 12:39 [Qemu-devel] [PATCH 0/6] Implement constant folding and copy propagation in TCG Kirill Batuzov
2011-05-20 12:39 ` [Qemu-devel] [PATCH 1/6] Add TCG optimizations stub Kirill Batuzov
2011-05-20 18:12 ` Richard Henderson
2011-05-20 18:33 ` Richard Henderson
2011-05-20 12:39 ` [Qemu-devel] [PATCH 2/6] Add copy and constant propagation Kirill Batuzov
2011-05-20 18:22 ` Richard Henderson
2011-05-20 18:46 ` Paolo Bonzini
2011-05-20 19:41 ` Aurelien Jarno
2011-05-20 12:39 ` [Qemu-devel] [PATCH 3/6] Do constant folding for basic arithmetic operations Kirill Batuzov
2011-05-20 12:39 ` [Qemu-devel] [PATCH 4/6] Do constant folding for boolean operations Kirill Batuzov
2011-05-20 18:45 ` Richard Henderson
2011-05-20 12:39 ` [Qemu-devel] [PATCH 5/6] Do constant folding for shift operations Kirill Batuzov
2011-05-20 18:37 ` Richard Henderson
2011-05-26 12:36 ` Kirill Batuzov
2011-05-26 13:56 ` Richard Henderson
2011-05-26 19:14 ` Blue Swirl
2011-05-26 20:10 ` Richard Henderson
2011-05-26 20:25 ` Blue Swirl
2011-05-26 21:14 ` Richard Henderson
2011-05-27 15:41 ` Jamie Lokier
2011-05-27 17:07 ` Blue Swirl [this message]
2011-05-27 19:54 ` Richard Henderson
2011-05-27 7:09 ` Paolo Bonzini
2011-05-20 12:39 ` [Qemu-devel] [PATCH 6/6] Do constant folding for unary operations Kirill Batuzov
2011-05-20 18:39 ` Richard Henderson
2011-05-20 17:50 ` [Qemu-devel] [PATCH 0/6] Implement constant folding and copy propagation in TCG Richard Henderson
2011-05-20 19:37 ` Aurelien Jarno
2011-05-20 23:31 ` Andreas Färber
2011-05-21 9:37 ` Laurent Desnogues
2011-05-21 10:46 ` Aurelien Jarno
2011-05-21 17:53 ` Kirill Batuzov
2011-05-20 19:35 ` Aurelien Jarno
2011-05-21 12:47 ` Dmitry Zhurikhin
2011-05-21 12:48 ` Aurelien Jarno
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