[flang][debug] Improve handling of cyclic derived types with classes.

[abidh]

While checking if a type should be cached or not, we use getDerivedType to peel outer layers and get to the base type. This function did not peel the fir.class which caused the algorithm to fail.

Fixes #128606.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

Author: Abid Qadeer (abidh)

Changes

While checking if a type should be cached or not, we use getDerivedType to peel outer layers and get to the base type. This function did not peel the fir.class which caused the algorithm to fail.

Fixes #128606.

---

Full diff: https://github.com/llvm/llvm-project/pull/129588.diff

2 Files Affected:

• (modified) flang/lib/Optimizer/Dialect/FIRType.cpp (+2-1)
• (added) flang/test/Integration/debug-cyclic-derived-type-4.f90 (+22)

diff --git a/flang/lib/Optimizer/Dialect/FIRType.cpp b/flang/lib/Optimizer/Dialect/FIRType.cpp
index 719cb1b9d75aa..f8fd55c79be12 100644
--- a/flang/lib/Optimizer/Dialect/FIRType.cpp
+++ b/flang/lib/Optimizer/Dialect/FIRType.cpp
@@ -210,7 +210,8 @@ mlir::Type getDerivedType(mlir::Type ty) {
           return seq.getEleTy();
         return p.getEleTy();
       })
-      .Case<fir::BoxType>([](auto p) { return getDerivedType(p.getEleTy()); })
+      .Case<fir::BaseBoxType>(
+          [](auto p) { return getDerivedType(p.getEleTy()); })
       .Default([](mlir::Type t) { return t; });
 }
 
diff --git a/flang/test/Integration/debug-cyclic-derived-type-4.f90 b/flang/test/Integration/debug-cyclic-derived-type-4.f90
new file mode 100644
index 0000000000000..783412e08ba7b
--- /dev/null
+++ b/flang/test/Integration/debug-cyclic-derived-type-4.f90
@@ -0,0 +1,22 @@
+! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck  %s
+
+! Same as debug-cyclic-derived-type-2.f90 but using class instead of type.
+module m
+ type t2
+   class(t1), pointer :: p1
+ end type
+ type t1
+   class(t2), pointer :: p2
+   integer abc
+ end type
+ type(t1) :: tee1
+end module
+
+program test
+  use m
+  type(t2) :: lc2
+  print *, lc2%p1%abc
+end program test
+
+! CHECK-DAG: DICompositeType(tag: DW_TAG_structure_type, name: "t1"{{.*}})
+! CHECK-DAG: DICompositeType(tag: DW_TAG_structure_type, name: "t2"{{.*}})

[jeanPerier]

Makes sense, thanks!