[clang] [CIR] Upstream global initialization for ComplexType (PR #141369)

[Henrich Lauko via cfe-commits]

================
@@ -577,12 +577,31 @@ mlir::Attribute ConstantEmitter::tryEmitPrivate(const APValue &value,
   case APValue::Union:
     cgm.errorNYI("ConstExprEmitter::tryEmitPrivate struct or union");
     return {};
-  case APValue::FixedPoint:
   case APValue::ComplexInt:
-  case APValue::ComplexFloat:
+  case APValue::ComplexFloat: {
+    mlir::Type desiredType = cgm.convertType(destType);
+    cir::ComplexType complexType =
+        mlir::dyn_cast<cir::ComplexType>(desiredType);
+
+    mlir::Type compelxElemTy = complexType.getElementType();
----------------
xlauko wrote:

```suggestion
    mlir::Type complexElemTy = complexType.getElementType();
```

https://github.com/llvm/llvm-project/pull/141369