DWARF Type Units: Avoid emitting type units under fission if the type requires an address.

Since there's no way to ensure the type unit in the .dwo and the type
unit skeleton in the .o are correlated, this cannot work.

This implementation is a bit inefficient for a few reasons, called out
in comments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207323 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 54 insertions, 7 deletions

diff --git a/lib/CodeGen/AsmPrinter/AddressPool.cpp b/lib/CodeGen/AsmPrinter/AddressPool.cpp
index 222717b81b..8dab5e59d6 100644
--- a/lib/CodeGen/AsmPrinter/AddressPool.cpp
+++ b/lib/CodeGen/AsmPrinter/AddressPool.cpp
@@ -17,6 +17,7 @@ using namespace llvm;
 class MCExpr;
 
 unsigned AddressPool::getIndex(const MCSymbol *Sym, bool TLS) {
+  HasBeenUsed = true;
   auto IterBool =
       Pool.insert(std::make_pair(Sym, AddressPoolEntry(Pool.size(), TLS)));
   return IterBool.first->second.Number;
diff --git a/lib/CodeGen/AsmPrinter/AddressPool.h b/lib/CodeGen/AsmPrinter/AddressPool.h
index d0c9b0d857..3058fed33f 100644
--- a/lib/CodeGen/AsmPrinter/AddressPool.h
+++ b/lib/CodeGen/AsmPrinter/AddressPool.h
@@ -26,8 +26,11 @@ class AddressPool {
     AddressPoolEntry(unsigned Number, bool TLS) : Number(Number), TLS(TLS) {}
   };
   DenseMap<const MCSymbol *, AddressPoolEntry> Pool;
+  bool HasBeenUsed;
 
 public:
+  AddressPool() : HasBeenUsed(false) {}
+
   /// \brief Returns the index into the address pool with the given
   /// label/symbol.
   unsigned getIndex(const MCSymbol *Sym, bool TLS = false);
@@ -35,6 +38,10 @@ public:
   void emit(AsmPrinter &Asm, const MCSection *AddrSection);
 
   bool isEmpty() { return Pool.empty(); }
+
+  bool hasBeenUsed() const { return HasBeenUsed; }
+
+  void resetUsedFlag() { HasBeenUsed = false; }
 };
 }
 #endif
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index cbd2eb6ca4..0465b8929a 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2500,19 +2500,28 @@ static uint64_t makeTypeSignature(StringRef Identifier) {
 void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
                                       StringRef Identifier, DIE &RefDie,
                                       DICompositeType CTy) {
+  // Fast path if we're building some type units and one has already used the
+  // address pool we know we're going to throw away all this work anyway, so
+  // don't bother building dependent types.
+  if (!TypeUnitsUnderConstruction.empty() && AddrPool.hasBeenUsed())
+    return;
+
   const DwarfTypeUnit *&TU = DwarfTypeUnits[CTy];
   if (TU) {
     CU.addDIETypeSignature(RefDie, *TU);
     return;
   }
 
+  bool TopLevelType = TypeUnitsUnderConstruction.empty();
+  AddrPool.resetUsedFlag();
+
   DIE *UnitDie = new DIE(dwarf::DW_TAG_type_unit);
   auto OwnedUnit =
       make_unique<DwarfTypeUnit>(InfoHolder.getUnits().size(), UnitDie, CU, Asm,
                                  this, &InfoHolder, getDwoLineTable(CU));
   DwarfTypeUnit &NewTU = *OwnedUnit;
   TU = &NewTU;
-  InfoHolder.addUnit(std::move(OwnedUnit));
+  TypeUnitsUnderConstruction.push_back(std::make_pair(std::move(OwnedUnit), CTy));
 
   NewTU.addUInt(*UnitDie, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
                 CU.getLanguage());
@@ -2520,9 +2529,7 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
   uint64_t Signature = makeTypeSignature(Identifier);
   NewTU.setTypeSignature(Signature);
 
-  if (useSplitDwarf())
-    NewTU.setSkeleton(constructSkeletonTU(NewTU));
-  else
+  if (!useSplitDwarf())
     CU.applyStmtList(*UnitDie);
 
   NewTU.initSection(
@@ -2532,6 +2539,36 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
 
   NewTU.setType(NewTU.createTypeDIE(CTy));
 
+  if (TopLevelType) {
+    auto TypeUnitsToAdd = std::move(TypeUnitsUnderConstruction);
+    TypeUnitsUnderConstruction.clear();
+
+    // Types referencing entries in the address table cannot be placed in type
+    // units.
+    if (AddrPool.hasBeenUsed()) {
+
+      // Remove all the types built while building this type.
+      // This is pessimistic as some of these types might not be dependent on
+      // the type that used an address.
+      for (const auto &TU : TypeUnitsToAdd)
+        DwarfTypeUnits.erase(TU.second);
+
+      // Construct this type in the CU directly.
+      // This is inefficient because all the dependent types will be rebuilt
+      // from scratch, including building them in type units, discovering that
+      // they depend on addresses, throwing them out and rebuilding them.
+      CU.constructTypeDIE(RefDie, CTy);
+      return;
+    }
+
+    // If the type wasn't dependent on fission addresses, finish adding the type
+    // and all its dependent types.
+    for (auto &TU : TypeUnitsToAdd) {
+      if (useSplitDwarf())
+        TU.first->setSkeleton(constructSkeletonTU(*TU.first));
+      InfoHolder.addUnit(std::move(TU.first));
+    }
+  }
   CU.addDIETypeSignature(RefDie, NewTU);
 }
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 9038c648af..a5bbb25122 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -284,6 +284,8 @@ class DwarfDebug : public AsmPrinterHandler {
   // them.
   DenseMap<const MDNode *, const DwarfTypeUnit *> DwarfTypeUnits;
 
+  SmallVector<std::pair<std::unique_ptr<DwarfTypeUnit>, DICompositeType>, 1> TypeUnitsUnderConstruction;
+
   // Whether to emit the pubnames/pubtypes sections.
   bool HasDwarfPubSections;
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfUnit.h b/lib/CodeGen/AsmPrinter/DwarfUnit.h
index 1e64f58fe0..69774f551b 100644
--- a/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -445,6 +445,9 @@ public:
 
   virtual DwarfCompileUnit &getCU() = 0;
 
+  /// constructTypeDIE - Construct type DIE from DICompositeType.
+  void constructTypeDIE(DIE &Buffer, DICompositeType CTy);
+
 protected:
   /// getOrCreateStaticMemberDIE - Create new static data member DIE.
   DIE *getOrCreateStaticMemberDIE(DIDerivedType DT);
@@ -465,9 +468,6 @@ private:
   /// constructTypeDIE - Construct derived type die from DIDerivedType.
   void constructTypeDIE(DIE &Buffer, DIDerivedType DTy);
 
-  /// constructTypeDIE - Construct type DIE from DICompositeType.
-  void constructTypeDIE(DIE &Buffer, DICompositeType CTy);
-
   /// constructSubrangeDIE - Construct subrange DIE from DISubrange.
   void constructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy);