[clang] [HLSL][clang] Add elementwise builtin for atan2 (p3) (PR #110187)

[via cfe-commits]

zeroomega wrote:

We are seeing `Clang :: Sema/aarch64-sve-vector-trig-ops.c` test failure after this change got landed.

```
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /b/s/w/ir/x/w/llvm_build/bin/clang -cc1 -internal-isystem /b/s/w/ir/x/w/llvm_build/lib/clang/20/include -nostdsysteminc -triple aarch64 -target-feature +sve    -disable-O0-optnone -o - -fsyntax-only /b/s/w/ir/x/w/llvm-llvm-project/clang/test/Sema/aarch64-sve-vector-trig-ops.c -verify
+ /b/s/w/ir/x/w/llvm_build/bin/clang -cc1 -internal-isystem /b/s/w/ir/x/w/llvm_build/lib/clang/20/include -nostdsysteminc -triple aarch64 -target-feature +sve -disable-O0-optnone -o - -fsyntax-only /b/s/w/ir/x/w/llvm-llvm-project/clang/test/Sema/aarch64-sve-vector-trig-ops.c -verify
error: 'expected-error' diagnostics expected but not seen: 
  File /b/s/w/ir/x/w/llvm-llvm-project/clang/test/Sema/aarch64-sve-vector-trig-ops.c Line 27 (directive at /b/s/w/ir/x/w/llvm-llvm-project/clang/test/Sema/aarch64-sve-vector-trig-ops.c:28): 1st argument must be a vector, integer or floating point type
error: 'expected-error' diagnostics seen but not expected: 
  File /b/s/w/ir/x/w/llvm-llvm-project/clang/test/Sema/aarch64-sve-vector-trig-ops.c Line 27: 1st argument must be a floating point type (was 'svfloat32_t' (aka '__SVFloat32_t'))
2 errors generated.

--
```

There are multiple llvm test failures going on so it is a bit difficult to isolate every one of them. But this patch touched the failing test file. Could you take a look please?

https://github.com/llvm/llvm-project/pull/110187