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

[Farzon Lotfi via cfe-commits]

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@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm-only -disable-llvm-passes -verify -DTEST_FUNC=__builtin_elementwise_atan2
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm-only -disable-llvm-passes -verify -DTEST_FUNC=__builtin_elementwise_pow
+
+double2 test_double_builtin(double2 p0, double2 p1) {
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farzonl wrote:

```suggestion
double test_double_builtin(double p0, double p1) {
  return TEST_FUNC(p0, p1);
  // expected-error at -1 {{passing 'double' to parameter of incompatible type 'float'}}
}

double2 test_vec_double_builtin(double2 p0, double2 p1) {
```

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