[DebugInfo] Use underlying type of global variables with opaque type

rdar://144881938

Author: augusto2112

lib/IRGen/IRGenDebugInfo.cpp

@@ -3869,6 +3869,14 @@ void IRGenDebugInfoImpl::emitGlobalVariableDeclaration(
   if (Opts.DebugInfoLevel <= IRGenDebugInfoLevel::LineTables)
     return;
 
+  // If this global variable contains an opaque type, replace it with its
+  // underlying type.
+  if (auto UnderlyingType = IGM.substOpaqueTypesWithUnderlyingTypes(
+          DbgTy.getType()->getCanonicalType())) {
+    auto &TI = IGM.getTypeInfoForUnlowered(UnderlyingType);
+    DbgTy = DebugTypeInfo::getFromTypeInfo(UnderlyingType, TI, IGM);
+  }
+
   llvm::DIType *DITy = getOrCreateType(DbgTy);
   VarDecl *VD = nullptr;
   if (Loc)

test/DebugInfo/global_opaque_var.swift

@@ -0,0 +1,28 @@
+// RUN: %target-swift-frontend -primary-file %s -emit-ir -g -o - | %FileCheck %s
+
+public protocol TheProtocol {}
+
+public class TheClass: TheProtocol {
+}
+
+struct TheStruct<T> {
+  let t: T
+}
+
+func f() -> some TheProtocol {
+  let p: some TheProtocol = TheClass()
+  return p
+}
+
+let v = f()
+// CHECK: !DIGlobalVariable(name: "v", {{.*}}type: ![[CONST_TYPE:[0-9]+]]
+// CHECK: ![[CONST_TYPE]] = !DIDerivedType(tag: DW_TAG_const_type, baseType: ![[TYPE:[0-9]+]])
+// CHECK: ![[TYPE]] = !DICompositeType(tag: DW_TAG_structure_type, name: "TheClass"
+
+let v2 = TheStruct(t: f())
+// CHECK: !DIGlobalVariable(name: "v2", {{.*}}type: ![[CONST_TYPE_GEN:[0-9]+]]
+// CHECK: ![[CONST_TYPE_GEN]] = !DIDerivedType(tag: DW_TAG_const_type, baseType: ![[TYPE_GEN_1:[0-9]+]])
+// CHECK: ![[TYPE_GEN_1]] = !DICompositeType(tag: DW_TAG_structure_type{{.*}}elements: ![[TYPE_GEN_2:[0-9]+]]
+// CHECK: ![[TYPE_GEN_2]] = !{![[TYPE_GEN_3:[0-9]+]]}
+// CHECK: ![[TYPE_GEN_3]] = !DIDerivedType(tag: DW_TAG_member{{.*}}baseType: ![[TYPE_GEN:[0-9]+]]
+// CHECK: ![[TYPE_GEN]] = !DICompositeType(tag: DW_TAG_structure_type, name: "$s17global_opaque_var9TheStructVyAA0D5ClassCGD"