Re: [Qemu-devel] [PATCH 08/12] TCG/PPC: use TCG_REG_CALL_STACK instead of TCG_REG_R1

[Blue Swirl]

On Sat, Jul 2, 2011 at 1:02 PM, Andreas Färber <address@hidden> wrote:
> Am 02.07.2011 um 11:04 schrieb Blue Swirl:
>
>> On Sat, Jul 2, 2011 at 12:06 AM, malc <address@hidden> wrote:
>>>
>>> On Sat, 2 Jul 2011, Blue Swirl wrote:
>>>
>>>> On Tue, Jun 28, 2011 at 1:51 AM, malc <address@hidden> wrote:
>>>>>
>>>>> On Sun, 26 Jun 2011, Blue Swirl wrote:
>>>>>
>>>>>> Use TCG_REG_CALL_STACK instead of TCG_REG_R1 etc. for consistency.
>>>>>>
>>>>>
>>>>> This i'd rather avoid.
>>>>
>>>> Why? In addition to the consistency among targets, a magic constant is
>>>> replaced with a symbol which improves the documenting abilities and
>>>> readability of the code.
>>>
>>> Makes it harder to read for me personally.
>>
>> What about other people reading the code? With TCG_REG_CALL_STACK it's
>> pretty clear what is the purpose of the register, with '1' it is
>> assumed that the reader happens to know it. I don't think the exact
>> value is so interesting, or is register 1 somehow different from
>> others?
>
> I second malc's notion. This is ppc-specific code, and GPR1 (r1) is the
> designated stack pointer, that has nothing to do with TCG. Using some
> generic TCG define hides from the reader which reg is being used,
> potentially leading to nonsensical moves from r1 to TCG_... or vice versa.

OK, I'll drop the patch.

> If we do want a define, I would suggest something ppc-specific like r1 or
> sp.
>
> Andreas
>