[clang][DebugInfo] Add DW_AT_default_value support for template template parameters

After this patch, in the following snippet:
```
template <typename T> Foo {};

template <template <typename T> class CT = Foo> Bar {};

Bar<> b;
```

The debug-info entry for the `CT` template parameter will have
a `DW_AT_default_value (true)` attached to it.

Differential Revision: https://reviews.llvm.org/D139989

2 files changed, 21 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 7bfb63d..382b7f3 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2091,7 +2091,7 @@ CGDebugInfo::CollectTemplateParams(Optional<TemplateArgs> OArgs,
       TA.getAsTemplate().getAsTemplateDecl()->printQualifiedName(
           OS, getPrintingPolicy());
       TemplateParams.push_back(DBuilder.createTemplateTemplateParameter(
-          TheCU, Name, nullptr, OS.str()));
+          TheCU, Name, nullptr, OS.str(), defaultParameter));
       break;
     }
     case TemplateArgument::Pack:
diff --git a/clang/test/CodeGenCXX/debug-info-template-parameter.cpp b/clang/test/CodeGenCXX/debug-info-template-parameter.cpp
index 4c8d1eb..360cc1f 100644
--- a/clang/test/CodeGenCXX/debug-info-template-parameter.cpp
+++ b/clang/test/CodeGenCXX/debug-info-template-parameter.cpp
@@ -23,17 +23,37 @@
 // CXX17: [[THIRD]] = !DITemplateValueParameter(name: "b", type: !{{[0-9]*}}, defaulted: true, value: i1 true)
 // CHECK: [[FIFTH]] = !DITemplateTypeParameter(name: "d", type: !{{[0-9]*}}, defaulted: true)
 
+// CHECK: DILocalVariable(name: "b1", {{.*}}, type: ![[TEMPLATE_TYPE:[0-9]+]]
+// CHECK: [[TEMPLATE_TYPE]] = {{.*}}!DICompositeType({{.*}}, templateParams: ![[B1_TYPE:[0-9]+]]
+// CHECK: [[B1_TYPE]] = !{![[FIRST:[0-9]+]]}
+// CHECK: [[FIRST]] = !DITemplateValueParameter(tag: DW_TAG_GNU_template_template_param, name: "CT", value: !"qux")
+
+// CHECK: DILocalVariable(name: "b2", {{.*}}, type: ![[TEMPLATE_TYPE:[0-9]+]]
+// CHECK: [[TEMPLATE_TYPE]] = {{.*}}!DICompositeType({{.*}}, templateParams: ![[B2_TYPE:[0-9]+]]
+// CHECK: [[B2_TYPE]] = !{![[FIRST:[0-9]+]]}
+// CHECK: [[FIRST]] = !DITemplateValueParameter(tag: DW_TAG_GNU_template_template_param, name: "CT", defaulted: true, value: !"bar")
+
 template <typename T>
 class bar {
 };
 
+template <typename T>
+class qux {
+};
+
 template <typename T = char, int i = 3, bool b = true, int x = sizeof(T),
           typename d = bar<T>>
 class foo {
 };
 
+template <template <typename T> class CT = bar>
+class baz {
+};
+
 int main() {
   foo<int, 6, false, 3, double> f1;
   foo<> f2;
+  baz<qux> b1;
+  baz<> b2;
   return 0;
 }