Re: [Qemu-devel] [PATCH v7 21/52] tcg: Use offsets not indices for TCGv_*

[Philippe Mathieu-Daudé]

On 10/23/2017 02:37 PM, Emilio G. Cota wrote:
> On Fri, Oct 20, 2017 at 16:19:52 -0700, Richard Henderson wrote:
>> Using the offset of a temporary, relative to TCGContext, rather than
>> its index means that we don't use 0.  That leaves offset 0 free for
>> a NULL representation without having to leave index 0 unused.
[...]
>>  /* used to align parameters */
>> -#define TCG_CALL_DUMMY_ARG      ((TCGArg)(-1))
>> +#define TCG_CALL_DUMMY_ARG      ((TCGArg)0)
> 
> We're doing something clever here (on a first read I thought TCGContext
> was a typo), so I'd leave a comment somewhere. TCG_CALL_DUMMY_ARG might
> be a good place to do so; a copy of the commit's message should suffice.

agreed.