PR14759: Debug info support for C++ member pointers.

This works fine with GDB for member variable pointers, but GDB's support for
member function pointers seems to be quite unrelated to
DW_TAG_ptr_to_member_type. (see GDB bug 14998 for details)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171698 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DIBuilder.h

@@ -126,6 +126,11 @@ namespace llvm {
                              uint64_t AlignInBits = 0, 
                              StringRef Name = StringRef());
 
+    /// \brief Create debugging information entry for a pointer to member.
+    /// @param PointeeTy Type pointed to by this pointer.
+    /// @param Class Type for which this pointer points to members of.
+    DIType createMemberPointerType(DIType PointeeTy, DIType Class);
+
     /// createReferenceType - Create debugging information entry for a c++
     /// style reference or rvalue reference type.
     DIType createReferenceType(unsigned Tag, DIType RTy);

include/llvm/DebugInfo.h

@@ -354,6 +354,11 @@ namespace llvm {
     /// associated with one.
     MDNode *getObjCProperty() const;
 
+    DIType getClassType() const {
+      assert(getTag() == dwarf::DW_TAG_ptr_to_member_type);
+      return getFieldAs<DIType>(10);
+    }
+
     StringRef getObjCPropertyName() const {
       if (getVersion() > LLVMDebugVersion11)
         return StringRef();

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -784,6 +784,9 @@ void CompileUnit::constructTypeDIE(DIE &Buffer, DIDerivedType DTy) {
   if (Size && Tag != dwarf::DW_TAG_pointer_type)
     addUInt(&Buffer, dwarf::DW_AT_byte_size, 0, Size);
 
+  if (Tag == dwarf::DW_TAG_ptr_to_member_type)
+      addDIEEntry(&Buffer, dwarf::DW_AT_containing_type, dwarf::DW_FORM_ref4,
+                  getOrCreateTypeDIE(DTy.getClassType()));
   // Add source line info if available and TyDesc is not a forward declaration.
   if (!DTy.isForwardDecl())
     addSourceLine(&Buffer, DTy);

lib/IR/DIBuilder.cpp

@@ -229,6 +229,24 @@ DIType DIBuilder::createPointerType(DIType PointeeTy, uint64_t SizeInBits,
   return DIType(MDNode::get(VMContext, Elts));
 }
 
+DIType DIBuilder::createMemberPointerType(DIType PointeeTy, DIType Base) {
+  // Pointer types are encoded in DIDerivedType format.
+  Value *Elts[] = {
+    GetTagConstant(VMContext, dwarf::DW_TAG_ptr_to_member_type),
+    NULL, //TheCU,
+    NULL,
+    NULL, // Filename
+    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Line
+    ConstantInt::get(Type::getInt64Ty(VMContext), 0),
+    ConstantInt::get(Type::getInt64Ty(VMContext), 0),
+    ConstantInt::get(Type::getInt64Ty(VMContext), 0), // Offset
+    ConstantInt::get(Type::getInt32Ty(VMContext), 0), // Flags
+    PointeeTy,
+    Base
+  };
+  return DIType(MDNode::get(VMContext, Elts));
+}
+
 /// createReferenceType - Create debugging information entry for a reference
 /// type.
 DIType DIBuilder::createReferenceType(unsigned Tag, DIType RTy) {

lib/IR/DebugInfo.cpp

@@ -172,6 +172,7 @@ bool DIDescriptor::isDerivedType() const {
   switch (getTag()) {
   case dwarf::DW_TAG_typedef:
   case dwarf::DW_TAG_pointer_type:
+  case dwarf::DW_TAG_ptr_to_member_type:
   case dwarf::DW_TAG_reference_type:
   case dwarf::DW_TAG_rvalue_reference_type:
   case dwarf::DW_TAG_const_type:
@@ -423,6 +424,7 @@ bool DIType::Verify() const {
   unsigned Tag = getTag();
   if (!isBasicType() && Tag != dwarf::DW_TAG_const_type &&
       Tag != dwarf::DW_TAG_volatile_type && Tag != dwarf::DW_TAG_pointer_type &&
+      Tag != dwarf::DW_TAG_ptr_to_member_type &&
       Tag != dwarf::DW_TAG_reference_type &&
       Tag != dwarf::DW_TAG_rvalue_reference_type &&
       Tag != dwarf::DW_TAG_restrict_type && Tag != dwarf::DW_TAG_vector_type &&

test/DebugInfo/member-pointers.ll

@@ -0,0 +1,34 @@
+; RUN: llc -filetype=obj -O0 < %s > %t
+; RUN: llvm-dwarfdump %t | FileCheck %s
+; CHECK: DW_TAG_ptr_to_member_type
+; CHECK: DW_TAG_ptr_to_member_type
+; IR generated from clang -g with the following source:
+; struct S {
+; };
+;
+; int S::*x = 0;
+; void (S::*y)(int) = 0;
+
+; ModuleID = 'simple.cpp'
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@x = global i64 -1, align 8
+@y = global { i64, i64 } zeroinitializer, align 8
+
+!llvm.dbg.cu = !{!0}
+
+!0 = metadata !{i32 786449, i32 0, i32 4, metadata !"simple.cpp", metadata !"/home/blaikie/Development/scratch", metadata !"clang version 3.3 ", i1 true, i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !1, metadata !3} ; [ DW_TAG_compile_unit ] [/home/blaikie/Development/scratch/simple.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !2}
+!2 = metadata !{i32 0}
+!3 = metadata !{metadata !4}
+!4 = metadata !{metadata !5, metadata !10}
+!5 = metadata !{i32 786484, i32 0, null, metadata !"x", metadata !"x", metadata !"", metadata !6, i32 2, metadata !7, i32 0, i32 1, i64* @x} ; [ DW_TAG_variable ] [x] [line 2] [def]
+!6 = metadata !{i32 786473, metadata !"simple.cpp", metadata !"/home/blaikie/Development/scratch", null} ; [ DW_TAG_file_type ]
+!7 = metadata !{i32 786463, null, null, null, i32 0, i64 0, i64 0, i64 0, i32 0, metadata !8, metadata !9} ; [ DW_TAG_ptr_to_member_type ] [line 0, size 0, align 0, offset 0] [from int]
+!8 = metadata !{i32 786468, null, metadata !"int", null, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = metadata !{i32 786451, null, metadata !"S", metadata !6, i32 1, i64 8, i64 8, i32 0, i32 0, null, metadata !2, i32 0, null, null} ; [ DW_TAG_structure_type ] [S] [line 1, size 8, align 8, offset 0] [from ]
+!10 = metadata !{i32 786484, i32 0, null, metadata !"y", metadata !"y", metadata !"", metadata !6, i32 3, metadata !11, i32 0, i32 1, { i64, i64 }* @y} ; [ DW_TAG_variable ] [y] [line 3] [def]
+!11 = metadata !{i32 786463, null, null, null, i32 0, i64 0, i64 0, i64 0, i32 0, metadata !12, metadata !9} ; [ DW_TAG_ptr_to_member_type ] [line 0, size 0, align 0, offset 0] [from ]
+!12 = metadata !{i32 786453, i32 0, metadata !"", i32 0, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !13, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!13 = metadata !{null, metadata !8}