DebugInfo: Move type units into the debug_types section with appropriate comdat grouping and type unit headers

This commit does not complete the type units feature - there are issues
around fission support (skeletal type units, pubtypes/pubnames) and
hashing of some types including those containing references to types in
other type units.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197073 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -3056,19 +3056,17 @@ void DwarfDebug::addDwarfTypeUnitType(uint16_t Language, DIE *RefDie,
     // referenced type, or possibly walk the precomputed hashes of related types
     // at the end.
     uint64_t Signature = DIEHash().computeTypeSignature(*Die);
+    NewTU->setTypeSignature(Signature);
+    NewTU->setType(Die);
 
     // Remove the References vector and add the type hash.
     I->second.first = Signature;
     I->second.second = NULL;
 
     NewTU->initSection(
-        useSplitDwarf() ? Asm->getObjFileLowering().getDwarfInfoDWOSection()
-                        : Asm->getObjFileLowering().getDwarfInfoSection(),
-        // FIXME: This is subtle (using the info section even when
-        // this CU is in the dwo section) and necessary for the
-        // current arange code - ideally it should iterate
-        // skeleton units, not full units, if it's going to reference skeletons
-        useSplitDwarf() ? NULL : DwarfInfoSectionSym);
+        useSplitDwarf()
+            ? Asm->getObjFileLowering().getDwarfTypesDWOSection(Signature)
+            : Asm->getObjFileLowering().getDwarfTypesSection(Signature));
   }
 
   // Populate all the signatures.

lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -1997,3 +1997,27 @@ void DwarfUnit::emitHeader(const MCSection *ASection,
   Asm->OutStreamer.AddComment("Address Size (in bytes)");
   Asm->EmitInt8(Asm->getDataLayout().getPointerSize());
 }
+
+void DwarfTypeUnit::emitHeader(const MCSection *ASection,
+                               const MCSymbol *ASectionSym) const {
+  DwarfUnit::emitHeader(ASection, ASectionSym);
+  Asm->OutStreamer.AddComment("Type Signature");
+  Asm->OutStreamer.EmitIntValue(TypeSignature, sizeof(TypeSignature));
+  Asm->OutStreamer.AddComment("Type DIE Offset");
+  Asm->OutStreamer.EmitIntValue(Ty->getOffset(), sizeof(Ty->getOffset()));
+}
+
+void DwarfTypeUnit::initSection(const MCSection *Section) {
+  assert(!this->Section);
+  this->Section = Section;
+  // Since each type unit is contained in its own COMDAT section, the begin
+  // label and the section label are the same. Using the begin label emission in
+  // DwarfDebug to emit the section label as well is slightly subtle/sneaky, but
+  // the only other alternative of lazily constructing start-of-section labels
+  // and storing a mapping in DwarfDebug (or AsmPrinter).
+  this->SectionSym = this->LabelBegin =
+      Asm->GetTempSymbol(Section->getLabelBeginName(), getUniqueID());
+  this->LabelEnd =
+      Asm->GetTempSymbol(Section->getLabelEndName(), getUniqueID());
+  this->LabelRange = Asm->GetTempSymbol("gnu_ranges", getUniqueID());
+}

lib/CodeGen/AsmPrinter/DwarfUnit.h

@@ -413,14 +413,15 @@ public:
 
   /// Compute the size of a header for this unit, not including the initial
   /// length field.
-  unsigned getHeaderSize() const {
+  virtual unsigned getHeaderSize() const {
     return sizeof(int16_t) + // DWARF version number
            sizeof(int32_t) + // Offset Into Abbrev. Section
            sizeof(int8_t);   // Pointer Size (in bytes)
   }
 
   /// Emit the header for this unit, not including the initial length field.
-  void emitHeader(const MCSection *ASection, const MCSymbol *ASectionSym) const;
+  virtual void emitHeader(const MCSection *ASection,
+                          const MCSymbol *ASectionSym) const;
 
 protected:
   /// getOrCreateStaticMemberDIE - Create new static data member DIE.
@@ -513,12 +514,25 @@ public:
 class DwarfTypeUnit : public DwarfUnit {
 private:
   uint16_t Language;
+  uint64_t TypeSignature;
+  const DIE *Ty;
 
 public:
   DwarfTypeUnit(unsigned UID, DIE *D, uint16_t Language, AsmPrinter *A,
                 DwarfDebug *DW, DwarfFile *DWU);
 
+  void setTypeSignature(uint64_t Signature) { TypeSignature = Signature; }
+  void setType(const DIE *Ty) { this->Ty = Ty; }
+
   uint16_t getLanguage() const LLVM_OVERRIDE { return Language; }
+  /// Emit the header for this unit, not including the initial length field.
+  void emitHeader(const MCSection *ASection, const MCSymbol *ASectionSym) const
+      LLVM_OVERRIDE;
+  unsigned getHeaderSize() const LLVM_OVERRIDE {
+    return DwarfUnit::getHeaderSize() + sizeof(uint64_t) + // Type Signature
+           sizeof(uint32_t);                               // Type DIE Offset
+  }
+  void initSection(const MCSection *Section);
 };
 } // end llvm namespace
 #endif