Re: [Qemu-devel] [PATCH 5/6] Do constant folding for shift operations.

[Richard Henderson]

On 05/26/2011 12:14 PM, Blue Swirl wrote:
> On Thu, May 26, 2011 at 4:56 PM, Richard Henderson <address@hidden> wrote:
>> On 05/26/2011 05:36 AM, Kirill Batuzov 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.

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.


r~