Reimplement with better encapsulation

Author: Alex B

llvm/include/llvm/MC/MCStreamer.h

@@ -251,15 +251,6 @@ class MCStreamer {
   /// discussion for future inclusion.
   bool AllowAutoPadding = false;
 
-  // Flag specifying weather functions will have an offset into the line table
-  // where the line data for that function starts
-  bool GenerateFuncLineTableOffsets = false;
-
-  // Symbol that tracks the stream symbol for first line of the current function
-  // being generated. This symbol can be used to reference where the line
-  // entries for the function start in the generated line table.
-  MCSymbol *CurrentFuncFirstLineStreamSym;
-
 protected:
   MCFragment *CurFrag = nullptr;
 
@@ -322,23 +313,7 @@ class MCStreamer {
   void setAllowAutoPadding(bool v) { AllowAutoPadding = v; }
   bool getAllowAutoPadding() const { return AllowAutoPadding; }
 
-  void setGenerateFuncLineTableOffsets(bool v) {
-    GenerateFuncLineTableOffsets = v;
-  }
-  bool getGenerateFuncLineTableOffsets() const {
-    return GenerateFuncLineTableOffsets;
-  }
-
-  // Use the below functions to track the symbol that points to the current
-  // function's line info in the output stream.
-  void beginFunction() { CurrentFuncFirstLineStreamSym = nullptr; }
-  void emittedLineStreamSym(MCSymbol *StreamSym) {
-    if (!CurrentFuncFirstLineStreamSym)
-      CurrentFuncFirstLineStreamSym = StreamSym;
-  }
-  MCSymbol *getCurrentFuncFirstLineStreamSym() {
-    return CurrentFuncFirstLineStreamSym;
-  }
+  MCSymbol *emitLineTableLabel();
 
   /// When emitting an object file, create and emit a real label. When emitting
   /// textual assembly, this should do nothing to avoid polluting our output.

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -49,6 +49,12 @@ cl::opt<cl::boolOrDefault> AddLinkageNamesToDeclCallOrigins(
              "referenced by DW_AT_call_origin attributes. Enabled by default "
              "for -gsce debugger tuning."));
 
+static cl::opt<bool> EmitFuncLineTableOffsetsOption(
+    "emit-func-debug-line-table-offsets", cl::Hidden,
+    cl::desc("Include line table offset in function's debug info and emit end "
+             "sequence after each function's line data."),
+    cl::init(false));
+
 static bool AddLinkageNamesToDeclCallOriginsForTuning(const DwarfDebug *DD) {
   bool EnabledByDefault = DD->tuneForSCE();
   if (EnabledByDefault)
@@ -511,7 +517,8 @@ void DwarfCompileUnit::addWasmRelocBaseGlobal(DIELoc *Loc, StringRef GlobalName,
 // Find DIE for the given subprogram and attach appropriate DW_AT_low_pc
 // and DW_AT_high_pc attributes. If there are global variables in this
 // scope then create and insert DIEs for these variables.
-DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP) {
+DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP,
+                                                MCSymbol *LineTableSym) {
   DIE *SPDie = getOrCreateSubprogramDIE(SP, includeMinimalInlineScopes());
   SmallVector<RangeSpan, 2> BB_List;
   // If basic block sections are on, ranges for each basic block section has
@@ -526,11 +533,9 @@ DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP) {
           *DD->getCurrentFunction()))
     addFlag(*SPDie, dwarf::DW_AT_APPLE_omit_frame_ptr);
 
-  if (Asm->OutStreamer->getGenerateFuncLineTableOffsets() &&
-      Asm->OutStreamer->getCurrentFuncFirstLineStreamSym()) {
+  if (emitFuncLineTableOffsets() && LineTableSym) {
     addSectionLabel(
-        *SPDie, dwarf::DW_AT_LLVM_stmt_sequence,
-        Asm->OutStreamer->getCurrentFuncFirstLineStreamSym(),
+        *SPDie, dwarf::DW_AT_LLVM_stmt_sequence, LineTableSym,
         Asm->getObjFileLowering().getDwarfLineSection()->getBeginSymbol());
   }
 
@@ -1104,8 +1109,9 @@ sortLocalVars(SmallVectorImpl<DbgVariable *> &Input) {
 }
 
 DIE &DwarfCompileUnit::constructSubprogramScopeDIE(const DISubprogram *Sub,
-                                                   LexicalScope *Scope) {
-  DIE &ScopeDIE = updateSubprogramScopeDIE(Sub);
+                                                   LexicalScope *Scope,
+                                                   MCSymbol *LineTableSym) {
+  DIE &ScopeDIE = updateSubprogramScopeDIE(Sub, LineTableSym);
 
   if (Scope) {
     assert(!Scope->getInlinedAt());
@@ -1699,6 +1705,10 @@ bool DwarfCompileUnit::includeMinimalInlineScopes() const {
          (DD->useSplitDwarf() && !Skeleton);
 }
 
+bool DwarfCompileUnit::emitFuncLineTableOffsets() const {
+  return EmitFuncLineTableOffsetsOption;
+}
+
 void DwarfCompileUnit::addAddrTableBase() {
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   MCSymbol *Label = DD->getAddressPool().getLabel();

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

@@ -152,6 +152,8 @@ class DwarfCompileUnit final : public DwarfUnit {
 
   bool includeMinimalInlineScopes() const;
 
+  bool emitFuncLineTableOffsets() const;
+
   void initStmtList();
 
   /// Apply the DW_AT_stmt_list from this compile unit to the specified DIE.
@@ -207,10 +209,10 @@ class DwarfCompileUnit final : public DwarfUnit {
   void attachLowHighPC(DIE &D, const MCSymbol *Begin, const MCSymbol *End);
 
   /// Find DIE for the given subprogram and attach appropriate
-  /// DW_AT_low_pc and DW_AT_high_pc attributes. If there are global
-  /// variables in this scope then create and insert DIEs for these
-  /// variables.
-  DIE &updateSubprogramScopeDIE(const DISubprogram *SP);
+  /// DW_AT_low_pc, DW_AT_high_pc and DW_AT_LLVM_stmt_sequence attributes.
+  /// If there are global variables in this scope then create and insert DIEs
+  /// for these variables.
+  DIE &updateSubprogramScopeDIE(const DISubprogram *SP, MCSymbol *LineTableSym);
 
   void constructScopeDIE(LexicalScope *Scope, DIE &ParentScopeDIE);
 
@@ -254,8 +256,8 @@ class DwarfCompileUnit final : public DwarfUnit {
   DIE *getOrCreateContextDIE(const DIScope *Ty) override;
 
   /// Construct a DIE for this subprogram scope.
-  DIE &constructSubprogramScopeDIE(const DISubprogram *Sub,
-                                   LexicalScope *Scope);
+  DIE &constructSubprogramScopeDIE(const DISubprogram *Sub, LexicalScope *Scope,
+                                   MCSymbol *LineTableSym);
 
   DIE *createAndAddScopeChildren(LexicalScope *Scope, DIE &ScopeDIE);
 

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -170,12 +170,6 @@ static cl::opt<DwarfDebug::MinimizeAddrInV5> MinimizeAddrInV5Option(
                           "Stuff")),
     cl::init(DwarfDebug::MinimizeAddrInV5::Default));
 
-static cl::opt<bool> EmitFuncLineTableOffsetsOption(
-    "emit-func-debug-line-table-offsets", cl::Hidden,
-    cl::desc("Include line table offset in function's debug info and emit end "
-             "sequence after each function's line data."),
-    cl::init(false));
-
 static constexpr unsigned ULEB128PadSize = 4;
 
 void DebugLocDwarfExpression::emitOp(uint8_t Op, const char *Comment) {
@@ -447,8 +441,6 @@ DwarfDebug::DwarfDebug(AsmPrinter *A)
   Asm->OutStreamer->getContext().setDwarfVersion(DwarfVersion);
   Asm->OutStreamer->getContext().setDwarfFormat(Dwarf64 ? dwarf::DWARF64
                                                         : dwarf::DWARF32);
-  Asm->OutStreamer->setGenerateFuncLineTableOffsets(
-      EmitFuncLineTableOffsetsOption);
 }
 
 // Define out of line so we don't have to include DwarfUnit.h in DwarfDebug.h.
@@ -2230,11 +2222,10 @@ void DwarfDebug::beginFunctionImpl(const MachineFunction *MF) {
   if (SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug)
     return;
 
-  // Notify the streamer that we are beginning a function - this will reset the
-  // label pointing to the currently generated function's first line entry
-  Asm->OutStreamer->beginFunction();
-
   DwarfCompileUnit &CU = getOrCreateDwarfCompileUnit(SP->getUnit());
+  FunctionLineTableLabel = CU.emitFuncLineTableOffsets()
+                               ? Asm->OutStreamer->emitLineTableLabel()
+                               : nullptr;
 
   Asm->OutStreamer->getContext().setDwarfCompileUnitID(
       getDwarfCompileUnitIDForLineTable(CU));
@@ -2346,11 +2337,14 @@ void DwarfDebug::endFunctionImpl(const MachineFunction *MF) {
   }
 
   ProcessedSPNodes.insert(SP);
-  DIE &ScopeDIE = TheCU.constructSubprogramScopeDIE(SP, FnScope);
+  DIE &ScopeDIE =
+      TheCU.constructSubprogramScopeDIE(SP, FnScope, FunctionLineTableLabel);
   if (auto *SkelCU = TheCU.getSkeleton())
     if (!LScopes.getAbstractScopesList().empty() &&
         TheCU.getCUNode()->getSplitDebugInlining())
-      SkelCU->constructSubprogramScopeDIE(SP, FnScope);
+      SkelCU->constructSubprogramScopeDIE(SP, FnScope, FunctionLineTableLabel);
+
+  FunctionLineTableLabel = nullptr;
 
   // Construct call site entries.
   constructCallSiteEntryDIEs(*SP, TheCU, ScopeDIE, *MF);

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -408,6 +408,9 @@ class DwarfDebug : public DebugHandlerBase {
       std::pair<std::unique_ptr<DwarfTypeUnit>, const DICompositeType *>, 1>
       TypeUnitsUnderConstruction;
 
+  /// Symbol pointing to the current function's DWARF line table entries.
+  MCSymbol *FunctionLineTableLabel;
+
   /// Used to set a uniqe ID for a Type Unit.
   /// This counter represents number of DwarfTypeUnits created, not necessarily
   /// number of type units that will be emitted.

llvm/lib/MC/MCDwarf.cpp

@@ -104,20 +104,6 @@ void MCDwarfLineEntry::make(MCStreamer *MCOS, MCSection *Section) {
   // Get the current .loc info saved in the context.
   const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
 
-  // If functions need offsets into the generated line table, then we need to
-  // create a label referencing where the line was generated in the output
-  // stream
-  if (MCOS->getGenerateFuncLineTableOffsets() &&
-      !MCOS->getCurrentFuncFirstLineStreamSym()) {
-    MCSymbol *LineStreamLabel = MCOS->getContext().createTempSymbol();
-    MCOS->emittedLineStreamSym(LineStreamLabel);
-    MCDwarfLineEntry LabelLineEntry(LineSym, DwarfLoc, LineStreamLabel);
-    MCOS->getContext()
-        .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
-        .getMCLineSections()
-        .addLineEntry(LabelLineEntry, Section);
-  }
-
   // Create a (local) line entry with the symbol and the current .loc info.
   MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
 

llvm/lib/MC/MCStreamer.cpp

@@ -483,6 +483,20 @@ void MCStreamer::emitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
   Frame.End = (MCSymbol *)1;
 }
 
+MCSymbol *MCStreamer::emitLineTableLabel() {
+  // Create a label and insert it into the line table and return this label
+  const MCDwarfLoc &DwarfLoc = getContext().getCurrentDwarfLoc();
+
+  MCSymbol *LineStreamLabel = getContext().createTempSymbol();
+  MCDwarfLineEntry LabelLineEntry(nullptr, DwarfLoc, LineStreamLabel);
+  getContext()
+      .getMCDwarfLineTable(getContext().getDwarfCompileUnitID())
+      .getMCLineSections()
+      .addLineEntry(LabelLineEntry, getCurrentSectionOnly() /*Section*/);
+
+  return LineStreamLabel;
+}
+
 MCSymbol *MCStreamer::emitCFILabel() {
   // Return a dummy non-null value so that label fields appear filled in when
   // generating textual assembly.