Revert r198208 and reapply:

      r198196: Use a pointer to keep track of the skeleton unit for each normal unit and construct it up front.
      r198199: Reapply r198196 with a fix to zero initialize the skeleton pointer.
      r198202: Fix aranges and split dwarf by ensuring that the symbol and relocation back to the compile unit from the aranges section is to the skeleton unit and not the one in the dwo.

with a fix to use integer 0 for DW_AT_low_pc since the relocation to the text section symbol was causing issues with COFF. Accordingly remove addLocalLabelAddress and machinery since we're not currently using it.

llvm-svn: 198222

4 files changed, 52 insertions, 34 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index a30e8bbd954..acb25ccaaf1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -773,12 +773,6 @@ DwarfCompileUnit *DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
                  DIUnit.getLanguage());
   NewCU->addString(Die, dwarf::DW_AT_name, FN);
 
-  // 2.17.1 requires that we use DW_AT_low_pc for a single entry point
-  // into an entity. We're using 0 (or a NULL label) for this. For
-  // split dwarf it's in the skeleton CU so omit it here.
-  if (!useSplitDwarf())
-    NewCU->addLabelAddress(Die, dwarf::DW_AT_low_pc, NULL);
-
   // Define start line table label for each Compile Unit.
   MCSymbol *LineTableStartSym =
       Asm->GetTempSymbol("line_table_start", NewCU->getUniqueID());
@@ -831,11 +825,11 @@ DwarfCompileUnit *DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
   NewCU->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
-      DwarfInfoSectionSym);
+      useSplitDwarf() ? DwarfInfoDWOSectionSym : DwarfInfoSectionSym);
+
+  // If we're splitting the dwarf then construct the skeleton CU now.
+  if (useSplitDwarf())
+    NewCU->setSkeleton(constructSkeletonCU(NewCU));
 
   CUMap.insert(std::make_pair(DIUnit, NewCU));
   CUDieMap.insert(std::make_pair(Die, NewCU));
@@ -1082,7 +1076,9 @@ void DwarfDebug::finalizeModuleInfo() {
     // Add CU specific attributes if we need to add any.
     if (TheU->getUnitDie()->getTag() == dwarf::DW_TAG_compile_unit) {
       // If we're splitting the dwarf out now that we've got the entire
-      // CU then construct a skeleton CU based upon it.
+      // CU then add the dwo id to it.
+      DwarfCompileUnit *SkCU =
+          static_cast<DwarfCompileUnit *>(TheU->getSkeleton());
       if (useSplitDwarf()) {
         // This should be a unique identifier when we want to build .dwp files.
         uint64_t ID = 0;
@@ -1092,19 +1088,21 @@ void DwarfDebug::finalizeModuleInfo() {
         }
         TheU->addUInt(TheU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
                       dwarf::DW_FORM_data8, ID);
-        // Now construct the skeleton CU associated.
-        DwarfCompileUnit *SkCU =
-            constructSkeletonCU(static_cast<DwarfCompileUnit *>(TheU));
         SkCU->addUInt(SkCU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
                       dwarf::DW_FORM_data8, ID);
-      } else {
-        // Attribute if we've emitted a range list for the compile unit, this
-        // will get constructed for the skeleton CU separately if we have one.
-        if (DwarfCURanges && TheU->getRanges().size())
-          addSectionLabel(Asm, TheU, TheU->getUnitDie(), dwarf::DW_AT_ranges,
-                          Asm->GetTempSymbol("cu_ranges", TheU->getUniqueID()),
-                          DwarfDebugRangeSectionSym);
       }
+
+      // If we've requested ranges and have them emit a DW_AT_ranges attribute
+      // on the unit that will remain in the .o file, otherwise add a DW_AT_low_pc.
+      // FIXME: Also add a high pc if we can.
+      // FIXME: We should use ranges if we have multiple compile units.
+      DwarfCompileUnit *U = SkCU ? SkCU : static_cast<DwarfCompileUnit *>(TheU);
+      if (DwarfCURanges && TheU->getRanges().size())
+        addSectionLabel(Asm, U, U->getUnitDie(), dwarf::DW_AT_ranges,
+                        Asm->GetTempSymbol("cu_ranges", U->getUniqueID()),
+                        DwarfDebugRangeSectionSym);
+      else
+        U->addUInt(U->getUnitDie(), dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr, 0);
     }
   }
 
@@ -2007,6 +2005,9 @@ void DwarfDebug::emitSectionLabels() {
   // Dwarf sections base addresses.
   DwarfInfoSectionSym =
       emitSectionSym(Asm, TLOF.getDwarfInfoSection(), "section_info");
+  if (useSplitDwarf())
+    DwarfInfoDWOSectionSym =
+        emitSectionSym(Asm, TLOF.getDwarfInfoDWOSection(), "section_info_dwo");
   DwarfAbbrevSectionSym =
       emitSectionSym(Asm, TLOF.getDwarfAbbrevSection(), "section_abbrev");
   if (useSplitDwarf())
@@ -2872,7 +2873,7 @@ void DwarfDebug::emitDebugARanges() {
     Asm->OutStreamer.AddComment("DWARF Arange version number");
     Asm->EmitInt16(dwarf::DW_ARANGES_VERSION);
     Asm->OutStreamer.AddComment("Offset Into Debug Info Section");
-    Asm->EmitSectionOffset(CU->getLabelBegin(), CU->getSectionSym());
+    Asm->EmitSectionOffset(CU->getLocalLabelBegin(), CU->getLocalSectionSym());
     Asm->OutStreamer.AddComment("Address Size (in bytes)");
     Asm->EmitInt8(PtrSize);
     Asm->OutStreamer.AddComment("Segment Size (in bytes)");
@@ -2997,15 +2998,6 @@ DwarfCompileUnit *DwarfDebug::constructSkeletonCU(const DwarfCompileUnit *CU) {
   else
     NewCU->addSectionOffset(Die, dwarf::DW_AT_GNU_addr_base, 0);
 
-  // Attribute if we've emitted a range list for the compile unit, this
-  // will get constructed for the skeleton CU separately if we have one.
-  if (DwarfCURanges && CU->getRanges().size())
-    addSectionLabel(Asm, NewCU, Die, dwarf::DW_AT_ranges,
-                    Asm->GetTempSymbol("cu_ranges", CU->getUniqueID()),
-                    DwarfDebugRangeSectionSym);
-  else
-    NewCU->addUInt(Die, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr, 0);
-
   // DW_AT_stmt_list is a offset of line number information for this
   // compile unit in debug_line section.
   // FIXME: Should handle multiple compile units.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 10ce17fa2dd..b81688ea3f0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -429,7 +429,8 @@ class DwarfDebug : public AsmPrinterHandler {
   MCSymbol *DwarfStrSectionSym, *TextSectionSym, *DwarfDebugRangeSectionSym;
   MCSymbol *DwarfDebugLocSectionSym, *DwarfLineSectionSym, *DwarfAddrSectionSym;
   MCSymbol *FunctionBeginSym, *FunctionEndSym;
-  MCSymbol *DwarfAbbrevDWOSectionSym, *DwarfStrDWOSectionSym;
+  MCSymbol *DwarfInfoDWOSectionSym, *DwarfAbbrevDWOSectionSym;
+  MCSymbol *DwarfStrDWOSectionSym;
   MCSymbol *DwarfGnuPubNamesSectionSym, *DwarfGnuPubTypesSectionSym;
 
   // As an optimization, there is no need to emit an entry in the directory
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 693e37ffe8d..e32582e76b1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -43,7 +43,7 @@ GenerateDwarfTypeUnits("generate-type-units", cl::Hidden,
 DwarfUnit::DwarfUnit(unsigned UID, DIE *D, DICompileUnit Node, AsmPrinter *A,
                      DwarfDebug *DW, DwarfFile *DWU)
     : UniqueID(UID), Node(Node), UnitDie(D), DebugInfoOffset(0), Asm(A), DD(DW),
-      DU(DWU), IndexTyDie(0), Section(0) {
+      DU(DWU), IndexTyDie(0), Section(0), Skeleton(0) {
   DIEIntegerOne = new (DIEValueAllocator) DIEInteger(1);
 }
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
index 7d7b351b9b0..808c9c25ed3 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -146,12 +146,21 @@ protected:
   /// The label for the start of the range sets for the elements of this unit.
   MCSymbol *LabelRange;
 
+  /// Skeleton unit associated with this unit.
+  DwarfUnit *Skeleton;
+
   DwarfUnit(unsigned UID, DIE *D, DICompileUnit CU, AsmPrinter *A,
             DwarfDebug *DW, DwarfFile *DWU);
 
 public:
   virtual ~DwarfUnit();
 
+  /// Set the skeleton unit associated with this unit.
+  void setSkeleton(DwarfUnit *Skel) { Skeleton = Skel; }
+
+  /// Get the skeleton unit associated with this unit.
+  DwarfUnit *getSkeleton() const { return Skeleton; }
+
   /// Pass in the SectionSym even though we could recreate it in every compile
   /// unit (type units will have actually distinct symbols once they're in
   /// comdat sections).
@@ -171,11 +180,27 @@ public:
     return Section;
   }
 
+  /// If there's a skeleton then return the section symbol for the skeleton
+  /// unit, otherwise return the section symbol for this unit.
+  MCSymbol *getLocalSectionSym() const {
+    if (Skeleton)
+      return Skeleton->getSectionSym();
+    return SectionSym;
+  }
+
   MCSymbol *getSectionSym() const {
     assert(Section);
     return SectionSym;
   }
 
+  /// If there's a skeleton then return the begin label for the skeleton unit,
+  /// otherwise return the local label for this unit.
+  MCSymbol *getLocalLabelBegin() const {
+    if (Skeleton)
+      return Skeleton->getLabelBegin();
+    return LabelBegin;
+  }
+
   MCSymbol *getLabelBegin() const {
     assert(Section);
     return LabelBegin;