Re: [PATCH 2/2][GCC] arm: Declare MVE types internally via pragma

[Richard Earnshaw <Richard.Earnshaw@foss.arm.com>]

On 08/12/2021 15:39, Murray Steele via Gcc-patches wrote:
> Hi,
> 
> Thank you for the feedback, I'll make the noted changes to the changelog and
> add the missing end-of-namespace comments.
> 
> On 08/12/2021 15:23, Richard Earnshaw wrote:
> 
>> diff --git a/gcc/config/arm/arm-mve-builtins.def b/gcc/config/arm/arm-mve-builtins.def
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..02a46bec3e4cba6add9bce4021c732e15aa8b012
>> --- /dev/null
>> +++ b/gcc/config/arm/arm-mve-builtins.def
>> @@ -0,0 +1,41 @@
>>
>> +#ifndef DEF_MVE_TYPE
>> +#define DEF_MVE_TYPE(A, B)
>> +#endif
>>
>> When would this file ever be included when this macro wasn't defined? Better to require the caller to define this by using #error if it's missing.
>>
>> then...
>>
>> +
>> +#undef DEF_MVE_TYPE
>>
>> This isn't needed anymore, because caller should undef it after use.
> 
> 
> I'd added this because later patches that build from this series will most
> likely need to define further DEF_MVE_* macros, in the style of the current
> SVE implementation. You are right that it is unnecessary for right now though,
> and I'll remove it too.

The best thing to do in that case then is to require the caller to
explicitly define DEF_MVE_TYPE as a NOP when it isn't required.  It
means a bit more churn at each call site, but I think it's more robust
longer term as it is clear which operations are going to be extracted.

R.

> 
> Thanks again,
> 
> Murray
>