[BOLT][DWARF][NFC] Use SkeletonCU in place of IsDWO check (#82540)

Changed isDWO to a function that checks Skeleton CU that is passed in.
This is for preparation for
#81062.

Author: ayermolo

bolt/include/bolt/Core/DIEBuilder.h

@@ -124,7 +124,7 @@ class DIEBuilder {
   std::vector<std::unique_ptr<DIEAbbrev>> Abbreviations;
   BinaryContext &BC;
   DWARFContext *DwarfContext{nullptr};
-  bool IsDWO{false};
+  DWARFUnit *SkeletonCU{nullptr};
   uint64_t UnitSize{0};
   llvm::DenseSet<uint64_t> AllProcessed;
 
@@ -264,8 +264,12 @@ class DIEBuilder {
   /// current Section.
   DIE *constructDIEFast(DWARFDie &DDie, DWARFUnit &U, uint32_t UnitId);
 
+  /// Returns true if this DIEBUilder is for DWO Unit.
+  bool isDWO() const { return SkeletonCU != nullptr; }
+
 public:
-  DIEBuilder(BinaryContext &BC, DWARFContext *DwarfContext, bool IsDWO = false);
+  DIEBuilder(BinaryContext &BC, DWARFContext *DwarfContext,
+             DWARFUnit *SkeletonCU = nullptr);
 
   /// Returns enum to what we are currently processing.
   ProcessingType getCurrentProcessingState() { return getState().Type; }

bolt/lib/Core/DIEBuilder.cpp

@@ -179,8 +179,8 @@ void DIEBuilder::constructFromUnit(DWARFUnit &DU) {
 }
 
 DIEBuilder::DIEBuilder(BinaryContext &BC, DWARFContext *DwarfContext,
-                       bool IsDWO)
-    : BC(BC), DwarfContext(DwarfContext), IsDWO(IsDWO) {}
+                       DWARFUnit *SkeletonCU)
+    : BC(BC), DwarfContext(DwarfContext), SkeletonCU(SkeletonCU) {}
 
 static unsigned int getCUNum(DWARFContext *DwarfContext, bool IsDWO) {
   unsigned int CUNum = IsDWO ? DwarfContext->getNumDWOCompileUnits()
@@ -204,11 +204,11 @@ void DIEBuilder::buildTypeUnits(DebugStrOffsetsWriter *StrOffsetWriter,
                                        true);
     }
   }
-  const unsigned int CUNum = getCUNum(DwarfContext, IsDWO);
+  const unsigned int CUNum = getCUNum(DwarfContext, isDWO());
   getState().CloneUnitCtxMap.resize(CUNum);
   DWARFContext::unit_iterator_range CU4TURanges =
-      IsDWO ? DwarfContext->dwo_types_section_units()
-            : DwarfContext->types_section_units();
+      isDWO() ? DwarfContext->dwo_types_section_units()
+              : DwarfContext->types_section_units();
 
   getState().Type = ProcessingType::DWARF4TUs;
   for (std::unique_ptr<DWARFUnit> &DU : CU4TURanges)
@@ -218,8 +218,8 @@ void DIEBuilder::buildTypeUnits(DebugStrOffsetsWriter *StrOffsetWriter,
     constructFromUnit(*DU.get());
 
   DWARFContext::unit_iterator_range CURanges =
-      IsDWO ? DwarfContext->dwo_info_section_units()
-            : DwarfContext->info_section_units();
+      isDWO() ? DwarfContext->dwo_info_section_units()
+              : DwarfContext->info_section_units();
 
   // This handles DWARF4 CUs and DWARF5 CU/TUs.
   // Creating a vector so that for reference handling only DWARF5 CU/TUs are
@@ -242,11 +242,11 @@ void DIEBuilder::buildCompileUnits(const bool Init) {
   if (Init)
     BuilderState.reset(new State());
 
-  unsigned int CUNum = getCUNum(DwarfContext, IsDWO);
+  unsigned int CUNum = getCUNum(DwarfContext, isDWO());
   getState().CloneUnitCtxMap.resize(CUNum);
   DWARFContext::unit_iterator_range CURanges =
-      IsDWO ? DwarfContext->dwo_info_section_units()
-            : DwarfContext->info_section_units();
+      isDWO() ? DwarfContext->dwo_info_section_units()
+              : DwarfContext->info_section_units();
 
   // This handles DWARF4 CUs and DWARF5 CU/TUs.
   // Creating a vector so that for reference handling only DWARF5 CU/TUs are

bolt/lib/Rewrite/DWARFRewriter.cpp

@@ -709,7 +709,7 @@ void DWARFRewriter::updateDebugInfo() {
                                 : LegacyRangesSectionWriter.get();
     // Skipping CUs that failed to load.
     if (SplitCU) {
-      DIEBuilder DWODIEBuilder(BC, &(*SplitCU)->getContext(), true);
+      DIEBuilder DWODIEBuilder(BC, &(*SplitCU)->getContext(), Unit);
       DWODIEBuilder.buildDWOUnit(**SplitCU);
       std::string DWOName = updateDWONameCompDir(
           *Unit, *DIEBlder, *DIEBlder->getUnitDIEbyUnit(*Unit));