From: Paolo Bonzini <pbonzini@redhat.com>
To: Blue Swirl <blauwirbel@gmail.com>
Cc: mj.mccormack@samsung.com, Kirill Batuzov <batuzovk@ispras.ru>,
qemu-devel@nongnu.org, zhur@ispras.ru,
Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH 5/6] Do constant folding for shift operations.
Date: Fri, 27 May 2011 09:09:38 +0200 [thread overview]
Message-ID: <4DDF4E32.2060301@redhat.com> (raw)
In-Reply-To: <BANLkTi=u6r-wMhCpdXUq_8bwOBJThGU=GA@mail.gmail.com>
On 05/26/2011 09:14 PM, Blue Swirl wrote:
>>>> x = (int32_t)x>> (int32_t)y;
>>>> >>>
>>> >> This expression has an implementation-defined behavior accroding to
>>> >> C99 6.5.7 so we decided to emulate signed shifts by hand.
>> >
>> > Technically, yes. In practice, no. GCC, ICC, LLVM, MSVC all know
>> > what the user wants here and will implement it "properly".
>
> Can't this be probed by configure? Then a wrapper could be introduced
> for signed shifts.
The reason for implementation-defined behavior is basically to allow for
non-two's-complement machine, which isn't really practical to support.
Paolo
next prev parent reply other threads:[~2011-05-27 7:09 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
2011-05-27 19:54 ` Richard Henderson
2011-05-27 7:09 ` Paolo Bonzini [this message]
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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