DwarfDebug: Omit DW_AT_object_pointer on inlined_subroutines

While refactoring out constructScopeDIE into two functions I realized we
were emitting DW_AT_object_pointer in the inlined subroutine when we
didn't need to (GCC doesn't, and the abstract subprogram definition has
the information already).

So here's the refactoring and the bug fix. This is one step of
refactoring to remove some subtle memory ownership semantics. It turns
out the original constructScopeDIE returned ownership in its return
value in some cases and not in others. The split into two functions now
separates those two semantics - further cleanup (unique_ptr, etc) will
follow.

llvm-svn: 207441

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -544,6 +544,43 @@ DIE *DwarfDebug::createScopeChildrenDIE(
   return ObjectPointer;
 }
 
+DIE *DwarfDebug::constructSubprogramScopeDIE(DwarfCompileUnit &TheCU, LexicalScope *Scope) {
+  assert(Scope && Scope->getScopeNode());
+
+  DIScope DS(Scope->getScopeNode());
+
+  assert(!Scope->getInlinedAt());
+  assert(DS.isSubprogram());
+
+  ProcessedSPNodes.insert(DS);
+
+  SmallVector<std::unique_ptr<DIE>, 8> Children;
+  DIE *ScopeDIE;
+
+  if (Scope->isAbstractScope()) {
+    ScopeDIE = TheCU.getDIE(DS);
+    // Note down abstract DIE.
+    if (ScopeDIE)
+      AbstractSPDies.insert(std::make_pair(DS, ScopeDIE));
+    else {
+      assert(Children.empty() &&
+             "We create children only when the scope DIE is not null.");
+      return nullptr;
+    }
+  } else
+    ScopeDIE = updateSubprogramScopeDIE(TheCU, DISubprogram(DS));
+
+  // We create children when the scope DIE is not null.
+  if (DIE *ObjectPointer = createScopeChildrenDIE(TheCU, Scope, Children))
+    TheCU.addDIEEntry(*ScopeDIE, dwarf::DW_AT_object_pointer, *ObjectPointer);
+
+  // Add children
+  for (auto &I : Children)
+    ScopeDIE->addChild(std::move(I));
+
+  return ScopeDIE;
+}
+
 // Construct a DIE for this scope.
 DIE *DwarfDebug::constructScopeDIE(DwarfCompileUnit &TheCU,
                                    LexicalScope *Scope) {
@@ -552,25 +589,23 @@ DIE *DwarfDebug::constructScopeDIE(DwarfCompileUnit &TheCU,
 
   DIScope DS(Scope->getScopeNode());
 
+  assert(Scope->getInlinedAt() ||
+         !DS.isSubprogram() && "Only handle inlined subprograms here, use "
+                               "constructSubprogramScopeDIE for non-inlined "
+                               "subprograms");
+
   SmallVector<std::unique_ptr<DIE>, 8> Children;
-  DIE *ObjectPointer = nullptr;
-  bool ChildrenCreated = false;
 
   // We try to create the scope DIE first, then the children DIEs. This will
   // avoid creating un-used children then removing them later when we find out
   // the scope DIE is null.
   DIE *ScopeDIE = nullptr;
-  if (Scope->getInlinedAt())
+  if (Scope->getInlinedAt()) {
     ScopeDIE = constructInlinedScopeDIE(TheCU, Scope);
-  else if (DS.isSubprogram()) {
-    ProcessedSPNodes.insert(DS);
-    if (Scope->isAbstractScope()) {
-      ScopeDIE = TheCU.getDIE(DS);
-      // Note down abstract DIE.
-      if (ScopeDIE)
-        AbstractSPDies.insert(std::make_pair(DS, ScopeDIE));
-    } else
-      ScopeDIE = updateSubprogramScopeDIE(TheCU, DISubprogram(DS));
+    if (!ScopeDIE)
+      return nullptr;
+    // We create children when the scope DIE is not null.
+    createScopeChildrenDIE(TheCU, Scope, Children);
   } else {
     // Early exit when we know the scope DIE is going to be null.
     if (isLexicalScopeDIENull(Scope))
@@ -578,8 +613,7 @@ DIE *DwarfDebug::constructScopeDIE(DwarfCompileUnit &TheCU,
 
     // We create children here when we know the scope DIE is not going to be
     // null and the children will be added to the scope DIE.
-    ObjectPointer = createScopeChildrenDIE(TheCU, Scope, Children);
-    ChildrenCreated = true;
+    createScopeChildrenDIE(TheCU, Scope, Children);
 
     // There is no need to emit empty lexical block DIE.
     std::pair<ImportedEntityMap::const_iterator,
@@ -596,24 +630,13 @@ DIE *DwarfDebug::constructScopeDIE(DwarfCompileUnit &TheCU,
     for (ImportedEntityMap::const_iterator i = Range.first; i != Range.second;
          ++i)
       constructImportedEntityDIE(TheCU, i->second, ScopeDIE);
-  }
 
-  if (!ScopeDIE) {
-    assert(Children.empty() &&
-           "We create children only when the scope DIE is not null.");
-    return nullptr;
   }
-  if (!ChildrenCreated)
-    // We create children when the scope DIE is not null.
-    ObjectPointer = createScopeChildrenDIE(TheCU, Scope, Children);
 
   // Add children
   for (auto &I : Children)
     ScopeDIE->addChild(std::move(I));
 
-  if (DS.isSubprogram() && ObjectPointer != nullptr)
-    TheCU.addDIEEntry(*ScopeDIE, dwarf::DW_AT_object_pointer, *ObjectPointer);
-
   return ScopeDIE;
 }
 
@@ -1655,10 +1678,10 @@ void DwarfDebug::endFunction(const MachineFunction *MF) {
       }
     }
     if (ProcessedSPNodes.count(AScope->getScopeNode()) == 0)
-      constructScopeDIE(TheCU, AScope);
+      constructSubprogramScopeDIE(TheCU, AScope);
   }
 
-  DIE &CurFnDIE = *constructScopeDIE(TheCU, FnScope);
+  DIE &CurFnDIE = *constructSubprogramScopeDIE(TheCU, FnScope);
   if (!CurFn->getTarget().Options.DisableFramePointerElim(*CurFn))
     TheCU.addFlag(CurFnDIE, dwarf::DW_AT_APPLE_omit_frame_ptr);
 

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -367,6 +367,8 @@ class DwarfDebug : public AsmPrinterHandler {
 
   /// \brief Construct a DIE for this scope.
   DIE *constructScopeDIE(DwarfCompileUnit &TheCU, LexicalScope *Scope);
+  /// \brief Construct a DIE for this scope.
+  DIE *constructSubprogramScopeDIE(DwarfCompileUnit &TheCU, LexicalScope *Scope);
   /// A helper function to create children of a Scope DIE.
   DIE *createScopeChildrenDIE(DwarfCompileUnit &TheCU, LexicalScope *Scope,
                               SmallVectorImpl<std::unique_ptr<DIE>> &Children);

llvm/test/DebugInfo/X86/inline-member-function.ll

@@ -0,0 +1,90 @@
+; REQUIRES: object-emission
+
+; RUN: llc -mtriple=x86_64-linux -O0 -filetype=obj < %s | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+; From source:
+; struct foo {
+;   int __attribute__((always_inline)) func(int x) { return x + 2; }
+; };
+
+; int i;
+
+; int main() {
+;   return foo().func(i);
+; }
+
+; Ensure we omit DW_AT_object_pointer on inlined subroutines.
+; CHECK: DW_TAG_inlined_subroutine
+; CHECK-NEXT: DW_AT_abstract_origin {{.*}}{[[ABSTRACT_ORIGIN:0x[0-9a-e]*]]}
+; CHECK-NOT: NULL
+; CHECK-NOT: DW_AT_object_pointer
+; CHECK: DW_TAG
+
+; But make sure we emit DW_AT_object_pointer on the abstract definition.
+; CHECK: [[ABSTRACT_ORIGIN]]: DW_TAG_subprogram
+; CHECK-NOT: NULL
+; CHECK-NOT: TAG
+; CHECK: DW_AT_object_pointer
+
+%struct.foo = type { i8 }
+
+@i = global i32 0, align 4
+
+; Function Attrs: uwtable
+define i32 @main() #0 {
+entry:
+  %this.addr.i = alloca %struct.foo*, align 8
+  %x.addr.i = alloca i32, align 4
+  %retval = alloca i32, align 4
+  %tmp = alloca %struct.foo, align 1
+  store i32 0, i32* %retval
+  %0 = load i32* @i, align 4, !dbg !23
+  store %struct.foo* %tmp, %struct.foo** %this.addr.i, align 8
+  call void @llvm.dbg.declare(metadata !{%struct.foo** %this.addr.i}, metadata !24), !dbg !26
+  store i32 %0, i32* %x.addr.i, align 4
+  call void @llvm.dbg.declare(metadata !{i32* %x.addr.i}, metadata !27), !dbg !28
+  %this1.i = load %struct.foo** %this.addr.i
+  %1 = load i32* %x.addr.i, align 4, !dbg !28
+  %add.i = add nsw i32 %1, 2, !dbg !28
+  ret i32 %add.i, !dbg !23
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata) #1
+
+attributes #0 = { uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!20, !21}
+!llvm.ident = !{!22}
+
+!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.5.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !3, metadata !12, metadata !18, metadata !2, metadata !"", i32 1} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/inline.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !"inline.cpp", metadata !"/tmp/dbginfo"}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786451, metadata !1, null, metadata !"foo", i32 1, i64 8, i64 8, i32 0, i32 0, null, metadata !5, i32 0, null, null, metadata !"_ZTS3foo"} ; [ DW_TAG_structure_type ] [foo] [line 1, size 8, align 8, offset 0] [def] [from ]
+!5 = metadata !{metadata !6}
+!6 = metadata !{i32 786478, metadata !1, metadata !"_ZTS3foo", metadata !"func", metadata !"func", metadata !"_ZN3foo4funcEi", i32 2, metadata !7, i1 false, i1 false, i32 0, i32 0, null, i32 256, i1 false, null, null, i32 0, metadata !11, i32 2} ; [ DW_TAG_subprogram ] [line 2] [func]
+!7 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !8, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!8 = metadata !{metadata !9, metadata !10, metadata !9}
+!9 = metadata !{i32 786468, null, null, metadata !"int", 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]
+!10 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 1088, metadata !"_ZTS3foo"} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [artificial] [from _ZTS3foo]
+!11 = metadata !{i32 786468}
+!12 = metadata !{metadata !13, metadata !17}
+!13 = metadata !{i32 786478, metadata !1, metadata !14, metadata !"main", metadata !"main", metadata !"", i32 7, metadata !15, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 ()* @main, null, null, metadata !2, i32 7} ; [ DW_TAG_subprogram ] [line 7] [def] [main]
+!14 = metadata !{i32 786473, metadata !1}         ; [ DW_TAG_file_type ] [/tmp/dbginfo/inline.cpp]
+!15 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !16, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!16 = metadata !{metadata !9}
+!17 = metadata !{i32 786478, metadata !1, metadata !"_ZTS3foo", metadata !"func", metadata !"func", metadata !"_ZN3foo4funcEi", i32 2, metadata !7, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, null, null, metadata !6, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 2] [def] [func]
+!18 = metadata !{metadata !19}
+!19 = metadata !{i32 786484, i32 0, null, metadata !"i", metadata !"i", metadata !"", metadata !14, i32 5, metadata !9, i32 0, i32 1, i32* @i, null} ; [ DW_TAG_variable ] [i] [line 5] [def]
+!20 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!21 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!22 = metadata !{metadata !"clang version 3.5.0 "}
+!23 = metadata !{i32 8, i32 0, metadata !13, null} ; [ DW_TAG_imported_declaration ]
+!24 = metadata !{i32 786689, metadata !17, metadata !"this", null, i32 16777216, metadata !25, i32 1088, i32 0} ; [ DW_TAG_arg_variable ] [this] [line 0]
+!25 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, metadata !"_ZTS3foo"} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from _ZTS3foo]
+!26 = metadata !{i32 0, i32 0, metadata !17, metadata !23}
+!27 = metadata !{i32 786689, metadata !17, metadata !"x", metadata !14, i32 33554434, metadata !9, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [x] [line 2]
+!28 = metadata !{i32 2, i32 0, metadata !17, metadata !23}