[clang] [Clang][SVE2.1] Make a part of the name optional for `svwhileXX` builtins with predicate-as-counter (PR #75200)

[Sander de Smalen via cfe-commits]

================
@@ -1,12 +1,20 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve2p1 -S -O1 -Werror -Wall -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve2p1 -S -O1 -Werror -Wall -emit-llvm -o - -x c++ %s | FileCheck %s -check-prefix=CPP-CHECK
+// RUN: %clang_cc1 -DSVE_OVERLOADED_FORMS -triple aarch64-none-linux-gnu -target-feature +sve2p1 -S -O1 -Werror -Wall -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -DSVE_OVERLOADED_FORMS -triple aarch64-none-linux-gnu -target-feature +sve2p1 -S -O1 -Werror -Wall -emit-llvm -o - -x c++ %s | FileCheck %s -check-prefix=CPP-CHECK
 // RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve2p1 -S -disable-O0-optnone -Werror -Wall -o /dev/null %s
----------------
sdesmalen-arm wrote:

I don't think we need to duplicate all RUN lines for `+sme2`. If we're choosing to use a single RUN line, I would like to suggest this one:

```
RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve2p1 -S -disable-O0-optnone -Werror -Wall -o /dev/null %s
```
(but with `-target-feature +sve -target-feature +sme2` instead of just `-target-feature +sve2p1`)

Because this tests the builtin -> asm flow and ensures we fully support the intrinsics end to end. We can probably trust the lowering from C/C++ -> LLVM IR to happen the same way as it does for SVE2p1, but if we want to have test coverage for that too we could keep one of the other RUN lines you've added in the current version of this patch/PR.

https://github.com/llvm/llvm-project/pull/75200