[fir] Add tests for mlir::ComplexType conversion

[rovka]

Summary

It turns out that mlir::ComplexType is translated the same way with or
without a conversion in TypeConverter.h. Add tests to make sure this
doesn't change in the future.

This patch is part of the upstreaming effort from fir-dev.

Co-authored-by: Eric Schweitz <[e-mail]>

[kiranchandramohan]

This might need a comment on why it is different from the regular mlir complex type conversion.

[kiranchandramohan]

In D113883#3131041, @kiranchandramohan wrote:

This might need a comment on why it is different from the regular mlir complex type conversion.

I am guessing this is for the target-specific conversion which is not available in the regular mlir complex type conversion.

[rovka]

In D113883#3131069, @kiranchandramohan wrote:

In D113883#3131041, @kiranchandramohan wrote:

This might need a comment on why it is different from the regular mlir complex type conversion.

I am guessing this is for the target-specific conversion which is not available in the regular mlir complex type conversion.

Good point. There's actually no target-specific conversion at this point, the target-specific parts are in the target-rewrite pass. I'm not sure why this conversion is needed here. Maybe @schweitz can explain.

[kiranchandramohan]

LGTM.

flang/test/Fir/types-to-llvm.fir

 // CHECK-SAME: !llvm.ptr<ptr<struct<(ptr<i32>, i{{.*}}, i{{.*}}, i{{.*}}, i{{.*}}, i{{.*}}, i{{.*}})>>>
 
 func private @foo3(%arg0: !fir.llvm_ptr<!fir.ptr<f32>>)
 // CHECK-LABEL: foo3
 // CHECK-SAME: !llvm.ptr<ptr<f32>>
 
 // -----
 
+// Test MLIR `complex<KIND>` conversion.
+
+func private @foo0(%arg0: complex<f16>)
+// CHECK-LABEL: foo0
+// CHECK-SAME: !llvm.struct<(f16, f16)>)
+
+func private @foo1(%arg0: complex<bf16>)
+// CHECK-LABEL: foo1
+// CHECK-SAME: !llvm.struct<(bf16, bf16)>)
+
+func private @foo2(%arg0: complex<f32>)
+// CHECK-LABEL: foo2
+// CHECK-SAME: !llvm.struct<(f32, f32)>)
+
+func private @foo3(%arg0: complex<f64>)
+// CHECK-LABEL: foo3
+// CHECK-SAME: !llvm.struct<(f64, f64)>)
+
+func private @foo4(%arg0: complex<f80>)
+// CHECK-LABEL: foo4
+// CHECK-SAME: !llvm.struct<(f80, f80)>)
+
+func private @foo5(%arg0: complex<f128>)
+// CHECK-LABEL: foo5
+// CHECK-SAME: !llvm.struct<(f128, f128)>)
+
+// -----
+
 // Test `!fir.complex<KIND>` conversion.
 
 func private @foo0(%arg0: !fir.complex<2>)
 // CHECK-LABEL: foo0
 // CHECK-SAME: !llvm.struct<(f16, f16)>)
 
 func private @foo1(%arg0: !fir.complex<3>)
 // CHECK-LABEL: foo1