Re: [Qemu-devel] [PATCH v2] target-mips: Fix incorrect shift for SHILO and SHILOV

[Peter Maydell]

On 5 December 2012 15:51, Richard Henderson <address@hidden> wrote:
> On 2012-12-05 09:49, Peter Maydell wrote:
>> On 5 December 2012 15:36, Richard Henderson <address@hidden> wrote:
>>> On 2012-12-04 17:29, Petar Jovanovic wrote:
>>>>      rs5_0 = (int8_t)(rs5_0 << 2) >> 2;
>>>
>>> This is more portably written as
>>>
>>>   rs5_0 = (rs5_0 ^ 0x20) - 0x20;
>>
>> ...but way more obscurely. If we want to play that
>> kind of game can we have a sign-extension function in
>> a header somewhere?
>
> I dunno about more obscurely.  It took me a minute to figure out
> what was wanted in the original.
>
> As for a helper function... sure.

I don't think we should block this patch on that general
cleanup, though. All the sign extensions in target-mips/translate.c
are done in the double-shift way, so this is consistent with
the existing code.

-- PMM