[Flang] Enable support for conversion of recursive record types

[kiranchandramohan]

Summary

Uses the recursive type conversion implemented in D113579, D113580.
Tests check for recursive and mutually recursive types.

Note: The downstream implementation for recursive types is a bit old and is based on a static map. This was removed while upstreaming (https://reviews.llvm.org/D112961) based on review comments. Since the recursive type conversion is now available in MLIR we are using that. If this patch is accepted we can use the same in the downstream implementation.
Part of upstreaming flang from fir-dev branch of https://github.com/flang-compiler/f18-llvm-project.

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

[kiranchandramohan]

Specify targets in test for conversion. Fixes the Windows CI failure.

flang/lib/Optimizer/CodeGen/TypeConverter.h

addConversion([&](fir::LogicalType boolTy) {
       return mlir::IntegerType::get(
           &getContext(), kindMapping.getLogicalBitsize(boolTy.getFKind()));
     });
     addConversion([&](fir::LLVMPointerType pointer) {
       return convertPointerLike(pointer);
     });
     addConversion(
         [&](fir::PointerType pointer) { return convertPointerLike(pointer); });
-    addConversion(
-        [&](fir::RecordType derived) { return convertRecordType(derived); });
+    addConversion([&](fir::RecordType derived, SmallVectorImpl<Type> &results,
+                      ArrayRef<Type> callStack) {
+      return convertRecordType(derived, results, callStack);
+    });
     addConversion([&](fir::FieldType field) {
       // Convert to i32 because of LLVM GEP indexing restriction.
       return mlir::IntegerType::get(field.getContext(), 32);
     });
     addConversion([&](fir::LenType field) {
       // Get size of len paramter from the descriptor.
       return getModel<Fortran::runtime::typeInfo::TypeParameterValue>()(
           &getContext());
public:
   // i32 is used here because LLVM wants i32 constants when indexing into struct
   // types. Indexing into other aggregate types is more flexible.
   mlir::Type offsetType() { return mlir::IntegerType::get(&getContext(), 32); }
 
   // i64 can be used to index into aggregates like arrays
   mlir::Type indexType() { return mlir::IntegerType::get(&getContext(), 64); }
 
   // fir.type<name(p : TY'...){f : TY...}>  -->  llvm<"%name = { ty... }">
-  mlir::Type convertRecordType(fir::RecordType derived) {
+  llvm::Optional<LogicalResult>
+  convertRecordType(fir::RecordType derived, SmallVectorImpl<Type> &results,
+                    ArrayRef<Type> callStack) {
     auto name = derived.getName();
     auto st = mlir::LLVM::LLVMStructType::getIdentified(&getContext(), name);
+    if (llvm::count(callStack, derived) > 1) {
+      results.push_back(st);
+      return success();
+    }
     llvm::SmallVector<mlir::Type> members;
     for (auto mem : derived.getTypeList()) {
       members.push_back(convertType(mem.second).cast<mlir::Type>());
     }
-    if (mlir::succeeded(st.setBody(members, /*isPacked=*/false)))
-      return st;
-    return mlir::Type();
+    if (mlir::failed(st.setBody(members, /*isPacked=*/false)))
+      return failure();
+    results.push_back(st);
+    return success();
   }
 
   // Is an extended descriptor needed given the element type of a fir.box type ?
   // Extended descriptors are required for derived types.
   bool requiresExtendedDesc(mlir::Type boxElementType) {
     auto eleTy = fir::unwrapSequenceType(boxElementType);
     return eleTy.isa<fir::RecordType>();
   }

flang/test/Fir/recursive-type.fir

+// Test lowering FIR to LLVM IR for recursive types
+  
+// RUN: fir-opt --fir-to-llvm-ir="target=x86_64-unknown-linux-gnu" %s | FileCheck %s
+// RUN: fir-opt --fir-to-llvm-ir="target=aarch64-unknown-linux-gnu" %s | FileCheck %s
+// RUN: fir-opt --fir-to-llvm-ir="target=i386-unknown-linux-gnu" %s | FileCheck %s
+// RUN: fir-opt --fir-to-llvm-ir="target=powerpc64le-unknown-linux-gn" %s | FileCheck %s
+
+!t1 = type !fir.type<t1 {a1:!fir.ptr<!fir.type<t1>>}>
+!t2 = type !fir.type<t2 {b1:f32,b2:!fir.ptr<!fir.type<t2>>,b3:i32,b4:!fir.ptr<!fir.type<t2>>}>
+!t3 = type !fir.type<t3 {c1:!fir.ptr<!fir.type<t4>>}>
+!t4 = type !fir.type<t4 {d1:!fir.ptr<!fir.type<t3>>}>
+
+// CHECK-LABEL: llvm.func @recursiveTypes
+// CHECK-SAME: %{{.*}}: !llvm.struct<"[[T1:.*]]", (ptr<struct<"[[T1]]">>)>
+// CHECK-SAME: %{{.*}}: !llvm.struct<"[[T2:.*]]", (f32, ptr<struct<"[[T2]]">>, i32, ptr<struct<"[[T2]]">>)>
+// CHECK-SAME: %{{.*}}: !llvm.struct<"[[T3:.*]]", (ptr<struct<"[[T4:.*]]", (ptr<struct<"[[T3]]">>)>>)>, %{{.*}}: !llvm.struct<"[[T4]]", (ptr<struct<"[[T3]]", (ptr<struct<"[[T4]]">>)>>)>)
+func @recursiveTypes(%a : !t1, %b : !t2, %c : !t3, %d : !t4) {
+  return
+}