[AccelTable] Provide abstraction for emitting DWARF5 accelerator tables.

When emitting the DWARF accelerator tables from dsymutil, we don't have
a DwarfDebug instance and we use a custom class to represent Dwarf
compile units. This patch adds an interface AccelTableWriterInfo to
abstract these from the Dwarf5AccelTableWriter, so we can have a custom
implementation for this in dsymutil.

Differential revision: https://reviews.llvm.org/D49031

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336529 91177308-0d34-0410-b5e6-96231b3b80d8

Author: JDevlieghere

include/llvm/CodeGen/AccelTable.h

@@ -122,8 +122,8 @@ class AccelTableData {
     return order() < Other.order();
   }
 
-  // Subclasses should implement:
-  // static uint32_t hash(StringRef Name);
+    // Subclasses should implement:
+    // static uint32_t hash(StringRef Name);
 
 #ifndef NDEBUG
   virtual void print(raw_ostream &OS) const = 0;
@@ -287,6 +287,25 @@ void emitDWARF5AccelTable(AsmPrinter *Asm,
                           const DwarfDebug &DD,
                           ArrayRef<std::unique_ptr<DwarfCompileUnit>> CUs);
 
+/// Abstraction to allow different users (DwarfDebug and dsymutil) to emit
+/// Dwarf accelerator tables.
+class AccelTableWriterInfo {
+public:
+  virtual ~AccelTableWriterInfo() = default;
+  virtual MCSymbol* getLabelForCU(unsigned Idx) const = 0;
+  virtual unsigned getNumberOfCUs() const = 0;
+  virtual unsigned getUnqiueIDForUnitDie(const DIE* UnitDie) const = 0;
+};
+
+void emitDWARF5AccelTable(AsmPrinter *Asm,
+                          AccelTable<DWARF5AccelTableData> &Contents,
+                          const DwarfDebug &DD,
+                          ArrayRef<std::unique_ptr<DwarfCompileUnit>> CUs);
+
+void emitDWARF5AccelTable(
+    AsmPrinter *Asm, AccelTable<DWARF5AccelTableData> &Contents,
+    std::unique_ptr<AccelTableWriterInfo> WriterInfo);
+
 /// Accelerator table data implementation for simple Apple accelerator tables
 /// with just a DIE reference.
 class AppleAccelTableOffsetData : public AppleAccelTableData {

lib/CodeGen/AsmPrinter/AccelTable.cpp

@@ -209,8 +209,7 @@ class Dwarf5AccelTableWriter : public AccelTableWriter {
 
   Header Header;
   DenseMap<uint32_t, SmallVector<AttributeEncoding, 2>> Abbreviations;
-  const DwarfDebug &DD;
-  ArrayRef<std::unique_ptr<DwarfCompileUnit>> CompUnits;
+  std::unique_ptr<AccelTableWriterInfo> WriterInfo;
   MCSymbol *ContributionStart = Asm->createTempSymbol("names_start");
   MCSymbol *ContributionEnd = Asm->createTempSymbol("names_end");
   MCSymbol *AbbrevStart = Asm->createTempSymbol("names_abbrev_start");
@@ -231,13 +230,47 @@ class Dwarf5AccelTableWriter : public AccelTableWriter {
 
 public:
   Dwarf5AccelTableWriter(AsmPrinter *Asm, const AccelTableBase &Contents,
-                         const DwarfDebug &DD,
-                         ArrayRef<std::unique_ptr<DwarfCompileUnit>> CompUnits);
+                          std::unique_ptr<AccelTableWriterInfo> WriterInfo);
 
   void emit() const;
 };
+
+/// Default emitter info used by DwarfDebug.
+class DefaultAccelTableWriterInfo final : public AccelTableWriterInfo {
+private:
+  const DwarfDebug &DD;
+  ArrayRef<std::unique_ptr<DwarfCompileUnit>> CompUnits;
+
+public:
+  DefaultAccelTableWriterInfo(const DwarfDebug &DD, ArrayRef<std::unique_ptr<DwarfCompileUnit>> CompUnits);
+  MCSymbol *getLabelForCU(unsigned Idx) const override;
+  unsigned getNumberOfCUs() const override;
+  unsigned getUnqiueIDForUnitDie(const DIE *UnitDie) const override;
+};
 } // namespace
 
+DefaultAccelTableWriterInfo::DefaultAccelTableWriterInfo(
+    const DwarfDebug &DD, ArrayRef<std::unique_ptr<DwarfCompileUnit>> CompUnits)
+    : DD(DD), CompUnits(CompUnits) {}
+
+MCSymbol *DefaultAccelTableWriterInfo::getLabelForCU(unsigned Idx) const {
+  assert(Idx < CompUnits.size());
+  const auto &CU = CompUnits[Idx];
+  assert(Idx == CU->getUniqueID());
+  const DwarfCompileUnit *MainCU =
+      DD.useSplitDwarf() ? CU->getSkeleton() : CU.get();
+  return MainCU->getLabelBegin();
+}
+
+unsigned DefaultAccelTableWriterInfo::getNumberOfCUs() const {
+  return CompUnits.size();
+}
+
+unsigned
+DefaultAccelTableWriterInfo::getUnqiueIDForUnitDie(const DIE *UnitDie) const {
+  return DD.lookupCU(UnitDie)->getUniqueID();
+}
+
 void AccelTableWriter::emitHashes() const {
   uint64_t PrevHash = std::numeric_limits<uint64_t>::max();
   unsigned BucketIdx = 0;
@@ -403,8 +436,8 @@ DenseSet<uint32_t> Dwarf5AccelTableWriter::getUniqueTags() const {
 SmallVector<Dwarf5AccelTableWriter::AttributeEncoding, 2>
 Dwarf5AccelTableWriter::getUniformAttributes() const {
   SmallVector<AttributeEncoding, 2> UA;
-  if (CompUnits.size() > 1) {
-    size_t LargestCUIndex = CompUnits.size() - 1;
+  if (WriterInfo->getNumberOfCUs() > 1) {
+    size_t LargestCUIndex = WriterInfo->getNumberOfCUs() - 1;
     dwarf::Form Form = DIEInteger::BestForm(/*IsSigned*/ false, LargestCUIndex);
     UA.push_back({dwarf::DW_IDX_compile_unit, Form});
   }
@@ -413,12 +446,10 @@ Dwarf5AccelTableWriter::getUniformAttributes() const {
 }
 
 void Dwarf5AccelTableWriter::emitCUList() const {
-  for (const auto &CU : enumerate(CompUnits)) {
-    assert(CU.index() == CU.value()->getUniqueID());
-    Asm->OutStreamer->AddComment("Compilation unit " + Twine(CU.index()));
-    const DwarfCompileUnit *MainCU =
-        DD.useSplitDwarf() ? CU.value()->getSkeleton() : CU.value().get();
-    Asm->emitDwarfSymbolReference(MainCU->getLabelBegin());
+  for (unsigned Idx = 0, CUs = WriterInfo->getNumberOfCUs(); Idx < CUs;
+       ++Idx) {
+    Asm->OutStreamer->AddComment("Compilation unit " + Twine(Idx));
+    Asm->emitDwarfSymbolReference(WriterInfo->getLabelForCU(Idx));
   }
 }
 
@@ -474,7 +505,7 @@ void Dwarf5AccelTableWriter::emitEntry(
     switch (AttrEnc.Index) {
     case dwarf::DW_IDX_compile_unit: {
       const DIE *CUDie = Entry.getDie().getUnitDie();
-      DIEInteger ID(DD.lookupCU(CUDie)->getUniqueID());
+      DIEInteger ID(WriterInfo->getUnqiueIDForUnitDie(CUDie));
       ID.EmitValue(Asm, AttrEnc.Form);
       break;
     }
@@ -503,12 +534,12 @@ void Dwarf5AccelTableWriter::emitData() const {
 }
 
 Dwarf5AccelTableWriter::Dwarf5AccelTableWriter(
-    AsmPrinter *Asm, const AccelTableBase &Contents, const DwarfDebug &DD,
-    ArrayRef<std::unique_ptr<DwarfCompileUnit>> CompUnits)
+    AsmPrinter *Asm, const AccelTableBase &Contents,
+    std::unique_ptr<AccelTableWriterInfo> WriterInfo)
     : AccelTableWriter(Asm, Contents, false),
-      Header(CompUnits.size(), Contents.getBucketCount(),
+      Header(WriterInfo->getNumberOfCUs(), Contents.getBucketCount(),
              Contents.getUniqueNameCount()),
-      DD(DD), CompUnits(CompUnits) {
+      WriterInfo(std::move(WriterInfo)) {
   DenseSet<uint32_t> UniqueTags = getUniqueTags();
   SmallVector<AttributeEncoding, 2> UniformAttributes = getUniformAttributes();
 
@@ -540,8 +571,15 @@ void llvm::emitAppleAccelTableImpl(AsmPrinter *Asm, AccelTableBase &Contents,
 void llvm::emitDWARF5AccelTable(
     AsmPrinter *Asm, AccelTable<DWARF5AccelTableData> &Contents,
     const DwarfDebug &DD, ArrayRef<std::unique_ptr<DwarfCompileUnit>> CUs) {
+  auto WriterInfo = llvm::make_unique<DefaultAccelTableWriterInfo>(DD, CUs);
+  emitDWARF5AccelTable(Asm, Contents, std::move(WriterInfo));
+}
+
+void llvm::emitDWARF5AccelTable(
+    AsmPrinter *Asm, AccelTable<DWARF5AccelTableData> &Contents,
+    std::unique_ptr<AccelTableWriterInfo> WriterInfo) {
   Contents.finalize(Asm, "names");
-  Dwarf5AccelTableWriter(Asm, Contents, DD, CUs).emit();
+  Dwarf5AccelTableWriter(Asm, Contents, std::move(WriterInfo)).emit();
 }
 
 void AppleAccelTableOffsetData::emit(AsmPrinter *Asm) const {