Add DwarfUnit::isDwoUnit and use it to generalize string creation

Currently we only need to emit skeleton strings into the CU header and
we do this by explicitly calling "addLocalString". With gmlt-in-fission,
we'll be emitting a bunch of other strings from other codepaths where
it's not statically known that these strings will be local or not.

Introduce a virtual function to indicate whether this unit is a DWO unit
or not (I'm not sure if we have a good term for this, the
opposite/alternative to 'skeleton' unit) and use that to generalize the
string emission logic so that strings can be correctly emitted in both
the skeleton and dwo unit when in split dwarf mode.

And to demonstrate that this works, switch the existing special callers
of addLocalString in the skeleton builder to addString - and they still
work. Yay.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221094 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -836,4 +836,8 @@ void DwarfCompileUnit::applySubprogramAttributesToDefinition(DISubprogram SP,
                                            DIBuilder::LineTablesOnly);
   addGlobalName(SP.getName(), SPDie, Context);
 }
+
+bool DwarfCompileUnit::isDwoUnit() const {
+  return DD->useSplitDwarf() && Skeleton;
+}
 } // end llvm namespace

lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

@@ -53,6 +53,8 @@ class DwarfCompileUnit : public DwarfUnit {
   std::unique_ptr<DIE> constructVariableDIEImpl(const DbgVariable &DV,
                                                 bool Abstract);
 
+  bool isDwoUnit() const override;
+
 public:
   DwarfCompileUnit(unsigned UID, DICompileUnit Node, AsmPrinter *A,
                    DwarfDebug *DW, DwarfFile *DWU);

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -362,6 +362,8 @@ DwarfCompileUnit &DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
   DwarfCompileUnit &NewCU = *OwnedUnit;
   DIE &Die = NewCU.getUnitDie();
   InfoHolder.addUnit(std::move(OwnedUnit));
+  if (useSplitDwarf())
+    NewCU.setSkeleton(constructSkeletonCU(NewCU));
 
   // LTO with assembly output shares a single line table amongst multiple CUs.
   // To avoid the compilation directory being ambiguous, let the line table
@@ -398,11 +400,10 @@ DwarfCompileUnit &DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
     NewCU.addUInt(Die, dwarf::DW_AT_APPLE_major_runtime_vers,
                   dwarf::DW_FORM_data1, RVer);
 
-  if (useSplitDwarf()) {
+  if (useSplitDwarf())
     NewCU.initSection(Asm->getObjFileLowering().getDwarfInfoDWOSection(),
                       DwarfInfoDWOSectionSym);
-    NewCU.setSkeleton(constructSkeletonCU(NewCU));
-  } else
+  else
     NewCU.initSection(Asm->getObjFileLowering().getDwarfInfoSection(),
                       DwarfInfoSectionSym);
 
@@ -2041,11 +2042,11 @@ void DwarfDebug::emitDebugRanges() {
 
 void DwarfDebug::initSkeletonUnit(const DwarfUnit &U, DIE &Die,
                                   std::unique_ptr<DwarfUnit> NewU) {
-  NewU->addLocalString(Die, dwarf::DW_AT_GNU_dwo_name,
+  NewU->addString(Die, dwarf::DW_AT_GNU_dwo_name,
                        U.getCUNode().getSplitDebugFilename());
 
   if (!CompilationDir.empty())
-    NewU->addLocalString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
+    NewU->addString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
 
   addGnuPubAttributes(*NewU, Die);
 

lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -201,10 +201,14 @@ void DwarfUnit::addSInt(DIELoc &Die, Optional<dwarf::Form> Form,
 /// table.
 void DwarfUnit::addString(DIE &Die, dwarf::Attribute Attribute,
                           StringRef String) {
-
-  if (!DD->useSplitDwarf())
+  if (!isDwoUnit())
     return addLocalString(Die, Attribute, String);
 
+  addIndexedString(Die, Attribute, String);
+}
+
+void DwarfUnit::addIndexedString(DIE &Die, dwarf::Attribute Attribute,
+                                 StringRef String) {
   unsigned idx = DU->getStringPool().getIndex(*Asm, String);
   DIEValue *Value = new (DIEValueAllocator) DIEInteger(idx);
   DIEValue *Str = new (DIEValueAllocator) DIEString(Value, String);
@@ -1632,3 +1636,8 @@ void DwarfTypeUnit::emitHeader(const MCSymbol *ASectionSym) const {
                                 sizeof(Ty->getOffset()));
 }
 
+bool DwarfTypeUnit::isDwoUnit() const {
+  // Since there are no skeleton type units, all type units are dwo type units
+  // when split DWARF is being used.
+  return DD->useSplitDwarf();
+}

lib/CodeGen/AsmPrinter/DwarfUnit.h

@@ -127,6 +127,12 @@ protected:
             DwarfDebug *DW, DwarfFile *DWU);
 
   void initSection(const MCSection *Section);
+
+  /// Add a string attribute data and value.
+  void addLocalString(DIE &Die, dwarf::Attribute Attribute, StringRef Str);
+
+  void addIndexedString(DIE &Die, dwarf::Attribute Attribute, StringRef Str);
+
 public:
   virtual ~DwarfUnit();
 
@@ -209,10 +215,6 @@ public:
   /// addString - Add a string attribute data and value.
   void addString(DIE &Die, dwarf::Attribute Attribute, StringRef Str);
 
-  /// addLocalString - Add a string attribute data and value.
-  void addLocalString(DIE &Die, dwarf::Attribute Attribute,
-                      StringRef Str);
-
   /// addLabel - Add a Dwarf label attribute data and value.
   void addLabel(DIE &Die, dwarf::Attribute Attribute, dwarf::Form Form,
                 const MCSymbol *Label);
@@ -412,15 +414,19 @@ private:
   /// If this is a named finished type then include it in the list of types for
   /// the accelerator tables.
   void updateAcceleratorTables(DIScope Context, DIType Ty, const DIE &TyDIE);
+
+  virtual bool isDwoUnit() const = 0;
 };
 
 class DwarfTypeUnit : public DwarfUnit {
-private:
   uint64_t TypeSignature;
   const DIE *Ty;
   DwarfCompileUnit &CU;
   MCDwarfDwoLineTable *SplitLineTable;
 
+  unsigned getOrCreateSourceID(StringRef File, StringRef Directory) override;
+  bool isDwoUnit() const override;
+
 public:
   DwarfTypeUnit(unsigned UID, DwarfCompileUnit &CU, AsmPrinter *A,
                 DwarfDebug *DW, DwarfFile *DWU,
@@ -438,9 +444,6 @@ public:
   }
   using DwarfUnit::initSection;
   DwarfCompileUnit &getCU() override { return CU; }
-
-protected:
-  unsigned getOrCreateSourceID(StringRef File, StringRef Directory) override;
 };
 } // end llvm namespace
 #endif