[Clang][SVE2.1] Add clang support for prototypes using svcount_t

[CarolineConcatto]

Summary

In this patch it is used for the prototype:

• svptrue_c8 (and _c16/_c32/_c64)
  
  As described in: https://github.com/ARM-software/acle/pull/257

Patch by: Sander de Smalen <[e-mail]>

[david-arm]

LGTM!

[sdesmalen]

clang/include/clang/Basic/Builtins.def

42

Can we make 'Q' something to mean 'target type' and then use a second letter to clarify which exact target type it is, e.g.

// Q -> target builtin type, followed by a character to distinguish the builtin type
//   Qa -> AArch64 svcount_t builtin type.

That should make it more extensible for other target types in the future.

[CarolineConcatto]

-Address review's comments about Q target type.

[hassnaa-arm]

clang/include/clang/Basic/Builtins.def

42

Is that suggestion because maybe other targets don't support svcount ?

[sdesmalen]

clang/include/clang/Basic/Builtins.def

42

Correct, svcount_t is an AArch64 specific type.

[hassnaa-arm]

clang/include/clang/Basic/Builtins.def

42

Thanks.

[sdesmalen]

clang/include/clang/Basic/arm_sve.td

56

The typespec modifier in this file can remain Q rather than Qa. Can you change it back?

[hassnaa-arm]

clang/include/clang/Basic/arm_sve.td

56

what if there is a new type that is target-specific ?
At that case we will have to find a new character.
But if we now use Qa, we can use Qb for the new type.
Is that correct ?

[CarolineConcatto]

• Remove Qa from arm_sve.td and its dependencies

[CarolineConcatto]

clang/include/clang/Basic/arm_sve.td

56

This is now removed. I thought that should reflect what is in Builtins.def, but it does not.
Because Q is being defined in sve target we do not the 'a' in 'Qa'