[DebugInfo][DWARF5]: Added support for debuginfo generation for defaulted parameters

This patch adds support for dwarf emission/dumping part of debuginfo
generation for defaulted parameters.

Reviewers: probinson, aprantl, dblaikie

Reviewed By: aprantl, dblaikie

Differential Revision: https://reviews.llvm.org/D73462

Author: Awanish Pandey

clang/test/CodeGenCXX/debug-info-template-parameter.cpp

@@ -0,0 +1,29 @@
+// Test for DebugInfo for Defaulted parameters for C++ templates
+// Supported: -O0, standalone DI
+
+// RUN: %clang_cc1 -dwarf-version=5  -emit-llvm -triple x86_64-linux-gnu %s -o - \
+// RUN:   -O0 -disable-llvm-passes \
+// RUN:   -debug-info-kind=standalone \
+// RUN: | FileCheck %s
+
+// CHECK: DILocalVariable(name: "f1", {{.*}}, type: ![[TEMPLATE_TYPE:[0-9]+]]
+// CHECK: [[TEMPLATE_TYPE]] = {{.*}}!DICompositeType({{.*}}, templateParams: ![[F1_TYPE:[0-9]+]]
+// CHECK: [[F1_TYPE]] = !{![[FIRST:[0-9]+]], ![[SECOND:[0-9]+]]}
+// CHECK: [[FIRST]] = !DITemplateTypeParameter(name: "T", type: !{{[0-9]*}})
+// CHECK: [[SECOND]] = !DITemplateValueParameter(name: "i", type: !{{[0-9]*}}, value: i32 6)
+
+// CHECK: DILocalVariable(name: "f2", {{.*}}, type: ![[TEMPLATE_TYPE:[0-9]+]]
+// CHECK: [[TEMPLATE_TYPE]] = {{.*}}!DICompositeType({{.*}}, templateParams: ![[F2_TYPE:[0-9]+]]
+// CHECK: [[F2_TYPE]] = !{![[FIRST:[0-9]+]], ![[SECOND:[0-9]+]]}
+// CHECK: [[FIRST]] = !DITemplateTypeParameter(name: "T", type: !{{[0-9]*}}, defaulted: true)
+// CHECK: [[SECOND]] = !DITemplateValueParameter(name: "i", type: !{{[0-9]*}}, defaulted: true, value: i32 3)
+
+template <typename T = char, int i = 3>
+class foo {
+};
+
+int main() {
+  foo<int, 6> f1;
+  foo<> f2;
+  return 0;
+}

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -1045,6 +1045,8 @@ void DwarfUnit::constructTemplateTypeParameterDIE(
     addType(ParamDIE, TP->getType());
   if (!TP->getName().empty())
     addString(ParamDIE, dwarf::DW_AT_name, TP->getName());
+  if (TP->isDefault() && (DD->getDwarfVersion() >= 5))
+    addFlag(ParamDIE, dwarf::DW_AT_default_value);
 }
 
 void DwarfUnit::constructTemplateValueParameterDIE(
@@ -1057,6 +1059,8 @@ void DwarfUnit::constructTemplateValueParameterDIE(
     addType(ParamDIE, VP->getType());
   if (!VP->getName().empty())
     addString(ParamDIE, dwarf::DW_AT_name, VP->getName());
+  if (VP->isDefault() && (DD->getDwarfVersion() >= 5))
+    addFlag(ParamDIE, dwarf::DW_AT_default_value);
   if (Metadata *Val = VP->getValue()) {
     if (ConstantInt *CI = mdconst::dyn_extract<ConstantInt>(Val))
       addConstantValue(ParamDIE, CI, VP->getType());