[PATCH] Remove wild .debug_aranges entries generated from unimportant labels

[Alexey Samsonov]

Hi echristo,

r191052 added emitting .debug_aranges to Clang, but this
functionality is broken: it uses all MC labels added in DWARF Asm
printer, including the labels for build relocations between
different DWARF sections, like .Lsection_line or .Ldebug_loc0.

As a result, if any DIE .debug_info would contain "DW_AT_location=0x123"
attribute, .debug_aranges would also contain a range starting from 0x123,
breaking tools that rely on this section.

I'm not sure this is the correct fix, please take a look.

http://llvm-reviews.chandlerc.com/D1809

Files:
  lib/CodeGen/AsmPrinter/DwarfDebug.cpp
  lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
  lib/CodeGen/AsmPrinter/DwarfDebug.h

Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1110,8 +1110,8 @@
 
 void DwarfDebug::endSections() {
    // Filter labels by section.
-  for (size_t n = 0; n < Labels.size(); n++) {
-    const SymbolCU &SCU = Labels[n];
+  for (size_t n = 0; n < ArangeLabels.size(); n++) {
+    const SymbolCU &SCU = ArangeLabels[n];
     if (SCU.Sym->isInSection()) {
       // Make a note of this symbol and it's section.
       const MCSection *Section = &SCU.Sym->getSection();
@@ -1138,10 +1138,7 @@
     }
 
     // Insert a final terminator.
-    SymbolCU Entry;
-    Entry.CU = NULL;
-    Entry.Sym = Sym;
-    SectionMap[Section].push_back(Entry);
+    SectionMap[Section].push_back(SymbolCU(NULL, Sym));
   }
 }
 
Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -181,26 +181,15 @@
                            const MCSymbol *Label) {
   DIEValue *Value = new (DIEValueAllocator) DIELabel(Label);
   Die->addValue(Attribute, Form, Value);
-
-  SymbolCU Entry;
-  Entry.CU = this;
-  Entry.Sym = Label;
-
-  DD->addLabel(Entry);
 }
 
 /// addLabelAddress - Add a dwarf label attribute data and value using
 /// DW_FORM_addr or DW_FORM_GNU_addr_index.
 ///
 void CompileUnit::addLabelAddress(DIE *Die, uint16_t Attribute,
                                   MCSymbol *Label) {
-  if (Label) {
-    SymbolCU Entry;
-    Entry.CU = this;
-    Entry.Sym = Label;
-
-    DD->addLabel(Entry);
-  }
+  if (Label)
+    DD->addArangeLabel(SymbolCU(this, Label));
 
   if (!DD->useSplitDwarf()) {
     if (Label != NULL) {
@@ -221,6 +210,7 @@
 /// form given and an op of either DW_FORM_addr or DW_FORM_GNU_addr_index.
 ///
 void CompileUnit::addOpAddress(DIE *Die, const MCSymbol *Sym) {
+  DD->addArangeLabel(SymbolCU(this, Sym));
   if (!DD->useSplitDwarf()) {
     addUInt(Die, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_addr);
     addLabel(Die, 0, dwarf::DW_FORM_udata, Sym);
Index: lib/CodeGen/AsmPrinter/DwarfDebug.h
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -303,6 +303,7 @@
 
 /// \brief Helper used to pair up a symbol and it's DWARF compile unit.
 struct SymbolCU {
+  SymbolCU(CompileUnit *CU, const MCSymbol *Sym) : Sym(Sym), CU(CU) {}
   const MCSymbol *Sym;
   CompileUnit *CU;
 };
@@ -363,8 +364,8 @@
   // separated by a zero byte, mapped to a unique id.
   StringMap<unsigned, BumpPtrAllocator&> SourceIdMap;
 
-  // List of all labels used in the output.
-  std::vector<SymbolCU> Labels;
+  // List of all labels used in aranges generation.
+  std::vector<SymbolCU> ArangeLabels;
 
   // Size of each symbol emitted (for those symbols that have a specific size).
   DenseMap <const MCSymbol *, uint64_t> SymSize;
@@ -731,7 +732,7 @@
   void addTypeUnitType(DIE *Die) { TypeUnits.push_back(Die); }
 
   /// \brief Add a label so that arange data can be generated for it.
-  void addLabel(SymbolCU SCU) { Labels.push_back(SCU); }
+  void addArangeLabel(SymbolCU SCU) { ArangeLabels.push_back(SCU); }
 
   /// \brief For symbols that have a size designated (e.g. common symbols),
   /// this tracks that size.
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