[clang] [CIR] Upstream ComplexType builtin_complex (PR #144225)

[Andy Kaylor via cfe-commits]

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@@ -176,3 +176,27 @@ void foo7() {
 // OGCG: store float %[[TMP_A]], ptr %[[C_REAL_PTR]], align 4
 // OGCG: store float 2.000000e+00, ptr %[[C_IMAG_PTR]], align 4
 
+void foo9(double r, double i) {
+  double _Complex c = __builtin_complex(r, i);
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andykaylor wrote:

Does `__builtin_complex` also accept integers? If so, add a test case for that.

I believe both arguments (or either) can also be an expression. So a test cases like this would be useful:

```
double _Complex c2 = __builtin_complex(a + b, a * 2.0);
double _Complex c3 = __builtin_complex(a + 1.0, 3.0);
```

https://github.com/llvm/llvm-project/pull/144225