DebugInfo: New metadata representation for global variables.

This patch reverses the edge from DIGlobalVariable to GlobalVariable.
This will allow us to more easily preserve debug info metadata when
manipulating global variables.

Fixes PR30362. A program for upgrading test cases is attached to that
bug.

Differential Revision: http://reviews.llvm.org/D20147

llvm-svn: 281284

6 files changed, 57 insertions, 64 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 017fc208870..91a480ec043 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -2001,6 +2001,14 @@ void CodeViewDebug::emitDebugInfoForUDTs(
 }
 
 void CodeViewDebug::emitDebugInfoForGlobals() {
+  DenseMap<const DIGlobalVariable *, const GlobalVariable *> GlobalMap;
+  for (const GlobalVariable &GV : MMI->getModule()->globals()) {
+    SmallVector<MDNode *, 1> MDs;
+    GV.getMetadata(LLVMContext::MD_dbg, MDs);
+    for (MDNode *MD : MDs)
+      GlobalMap[cast<DIGlobalVariable>(MD)] = &GV;
+  }
+
   NamedMDNode *CUs = MMI->getModule()->getNamedMetadata("llvm.dbg.cu");
   for (const MDNode *Node : CUs->operands()) {
     const auto *CU = cast<DICompileUnit>(Node);
@@ -2011,15 +2019,14 @@ void CodeViewDebug::emitDebugInfoForGlobals() {
     switchToDebugSectionForSymbol(nullptr);
     MCSymbol *EndLabel = nullptr;
     for (const DIGlobalVariable *G : CU->getGlobalVariables()) {
-      if (const auto *GV = dyn_cast_or_null<GlobalVariable>(G->getVariable())) {
+      if (const auto *GV = GlobalMap.lookup(G))
         if (!GV->hasComdat() && !GV->isDeclarationForLinker()) {
           if (!EndLabel) {
             OS.AddComment("Symbol subsection for globals");
             EndLabel = beginCVSubsection(ModuleSubstreamKind::Symbols);
           }
-          emitDebugInfoForGlobal(G, Asm->getSymbol(GV));
+          emitDebugInfoForGlobal(G, GV, Asm->getSymbol(GV));
         }
-      }
     }
     if (EndLabel)
       endCVSubsection(EndLabel);
@@ -2027,14 +2034,14 @@ void CodeViewDebug::emitDebugInfoForGlobals() {
     // Second, emit each global that is in a comdat into its own .debug$S
     // section along with its own symbol substream.
     for (const DIGlobalVariable *G : CU->getGlobalVariables()) {
-      if (const auto *GV = dyn_cast_or_null<GlobalVariable>(G->getVariable())) {
+      if (const auto *GV = GlobalMap.lookup(G)) {
         if (GV->hasComdat()) {
           MCSymbol *GVSym = Asm->getSymbol(GV);
           OS.AddComment("Symbol subsection for " +
                         Twine(GlobalValue::getRealLinkageName(GV->getName())));
           switchToDebugSectionForSymbol(GVSym);
           EndLabel = beginCVSubsection(ModuleSubstreamKind::Symbols);
-          emitDebugInfoForGlobal(G, GVSym);
+          emitDebugInfoForGlobal(G, GV, GVSym);
           endCVSubsection(EndLabel);
         }
       }
@@ -2055,6 +2062,7 @@ void CodeViewDebug::emitDebugInfoForRetainedTypes() {
 }
 
 void CodeViewDebug::emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
+                                           const GlobalVariable *GV,
                                            MCSymbol *GVSym) {
   // DataSym record, see SymbolRecord.h for more info.
   // FIXME: Thread local data, etc
@@ -2063,7 +2071,6 @@ void CodeViewDebug::emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
   OS.AddComment("Record length");
   OS.emitAbsoluteSymbolDiff(DataEnd, DataBegin, 2);
   OS.EmitLabel(DataBegin);
-  const auto *GV = cast<GlobalVariable>(DIGV->getVariable());
   if (DIGV->isLocalToUnit()) {
     if (GV->isThreadLocal()) {
       OS.AddComment("Record kind: S_LTHREAD32");
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index 729012bbd0f..0149af5e84f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -202,7 +202,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
   void emitDebugInfoForUDTs(
       ArrayRef<std::pair<std::string, codeview::TypeIndex>> UDTs);
 
-  void emitDebugInfoForGlobal(const DIGlobalVariable *DIGV, MCSymbol *GVSym);
+  void emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
+                              const GlobalVariable *GV, MCSymbol *GVSym);
 
   /// Opens a subsection of the given kind in a .debug$S codeview section.
   /// Returns an end label for use with endCVSubsection when the subsection is
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 7822814c7a0..f9030d118e5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -73,36 +73,9 @@ unsigned DwarfCompileUnit::getOrCreateSourceID(StringRef FileName,
       Asm->OutStreamer->hasRawTextSupport() ? 0 : getUniqueID());
 }
 
-// Return const expression if value is a GEP to access merged global
-// constant. e.g.
-// i8* getelementptr ({ i8, i8, i8, i8 }* @_MergedGlobals, i32 0, i32 0)
-static const ConstantExpr *getMergedGlobalExpr(const Value *V) {
-  const ConstantExpr *CE = dyn_cast_or_null<ConstantExpr>(V);
-  if (!CE || CE->getNumOperands() != 3 ||
-      CE->getOpcode() != Instruction::GetElementPtr)
-    return nullptr;
-
-  // First operand points to a global struct.
-  Value *Ptr = CE->getOperand(0);
-  GlobalValue *GV = dyn_cast<GlobalValue>(Ptr);
-  if (!GV || !isa<StructType>(GV->getValueType()))
-    return nullptr;
-
-  // Second operand is zero.
-  const ConstantInt *CI = dyn_cast_or_null<ConstantInt>(CE->getOperand(1));
-  if (!CI || !CI->isZero())
-    return nullptr;
-
-  // Third operand is offset.
-  if (!isa<ConstantInt>(CE->getOperand(2)))
-    return nullptr;
-
-  return CE;
-}
-
 /// getOrCreateGlobalVariableDIE - get or create global variable DIE.
 DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
-    const DIGlobalVariable *GV) {
+    const DIGlobalVariable *GV, const GlobalVariable *Global) {
   // Check for pre-existence.
   if (DIE *Die = getDIE(GV))
     return Die;
@@ -147,12 +120,22 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
 
   // Add location.
   bool addToAccelTable = false;
-  if (auto *Global = dyn_cast_or_null<GlobalVariable>(GV->getVariable())) {
+
+  DIExpression *Expr = GV->getExpr();
+
+  // For compatibility with DWARF 3 and earlier,
+  // DW_AT_location(DW_OP_constu, X, DW_OP_stack_value) becomes
+  // DW_AT_const_value(X).
+  if (Expr && Expr->getNumElements() == 3 &&
+      Expr->getElement(0) == dwarf::DW_OP_constu &&
+      Expr->getElement(2) == dwarf::DW_OP_stack_value) {
+    addConstantValue(*VariableDIE, /*Unsigned=*/true, Expr->getElement(1));
     // We cannot describe the location of dllimport'd variables: the computation
     // of their address requires loads from the IAT.
-    if (!Global->hasDLLImportStorageClass()) {
+  } else if (!Global || !Global->hasDLLImportStorageClass()) {
+    DIELoc *Loc = new (DIEValueAllocator) DIELoc;
+    if (Global) {
       addToAccelTable = true;
-      DIELoc *Loc = new (DIEValueAllocator) DIELoc;
       const MCSymbol *Sym = Asm->getSymbol(Global);
       if (Global->isThreadLocal()) {
         if (Asm->TM.Options.EmulatedTLS) {
@@ -187,30 +170,16 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
         addOpAddress(*Loc, Sym);
       }
 
-      addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
-      if (DD->useAllLinkageNames())
-        addLinkageName(*VariableDIE, GV->getLinkageName());
-    }
-  } else if (const ConstantInt *CI =
-                 dyn_cast_or_null<ConstantInt>(GV->getVariable())) {
-    addConstantValue(*VariableDIE, CI, GTy);
-  } else if (const ConstantExpr *CE = getMergedGlobalExpr(GV->getVariable())) {
-    auto *Ptr = cast<GlobalValue>(CE->getOperand(0));
-    if (!Ptr->hasDLLImportStorageClass()) {
-      addToAccelTable = true;
-      // GV is a merged global.
-      DIELoc *Loc = new (DIEValueAllocator) DIELoc;
-      MCSymbol *Sym = Asm->getSymbol(Ptr);
-      DD->addArangeLabel(SymbolCU(this, Sym));
-      addOpAddress(*Loc, Sym);
-      addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_constu);
-      SmallVector<Value *, 3> Idx(CE->op_begin() + 1, CE->op_end());
-      addUInt(*Loc, dwarf::DW_FORM_udata,
-              Asm->getDataLayout().getIndexedOffsetInType(Ptr->getValueType(),
-                                                          Idx));
-      addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);
-      addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
+      if (Expr) {
+        DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
+        DwarfExpr.AddExpression(Expr->expr_op_begin(), Expr->expr_op_end());
+      }
     }
+
+    addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
+
+    if (DD->useAllLinkageNames())
+      addLinkageName(*VariableDIE, GV->getLinkageName());
   }
 
   if (addToAccelTable) {
@@ -674,7 +643,7 @@ DIE *DwarfCompileUnit::constructImportedEntityDIE(
   else if (auto *T = dyn_cast<DIType>(Entity))
     EntityDie = getOrCreateTypeDIE(T);
   else if (auto *GV = dyn_cast<DIGlobalVariable>(Entity))
-    EntityDie = getOrCreateGlobalVariableDIE(GV);
+    EntityDie = getOrCreateGlobalVariableDIE(GV, nullptr);
   else
     EntityDie = getDIE(Entity);
   assert(EntityDie);
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 90f74a3686e..766da4a3f7b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -97,7 +97,8 @@ public:
   void applyStmtList(DIE &D);
 
   /// getOrCreateGlobalVariableDIE - get or create global variable DIE.
-  DIE *getOrCreateGlobalVariableDIE(const DIGlobalVariable *GV);
+  DIE *getOrCreateGlobalVariableDIE(const DIGlobalVariable *GV,
+                                    const GlobalVariable *Global);
 
   /// addLabelAddress - Add a dwarf label attribute data and value using
   /// either DW_FORM_addr or DW_FORM_GNU_addr_index.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 307782245a6..d9c7c2bea9e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -477,12 +477,20 @@ void DwarfDebug::beginModule() {
   MMI->setDebugInfoAvailability(NumDebugCUs > 0);
   SingleCU = NumDebugCUs == 1;
 
+  DenseMap<DIGlobalVariable *, const GlobalVariable *> GVMap;
+  for (const GlobalVariable &Global : M->globals()) {
+    SmallVector<DIGlobalVariable *, 1> GVs;
+    Global.getDebugInfo(GVs);
+    for (auto &GV : GVs)
+      GVMap[GV] = &Global;
+  }
+
   for (DICompileUnit *CUNode : M->debug_compile_units()) {
     DwarfCompileUnit &CU = constructDwarfCompileUnit(CUNode);
     for (auto *IE : CUNode->getImportedEntities())
       CU.addImportedEntity(IE);
     for (auto *GV : CUNode->getGlobalVariables())
-      CU.getOrCreateGlobalVariableDIE(GV);
+      CU.getOrCreateGlobalVariableDIE(GV, GVMap.lookup(GV));
     for (auto *Ty : CUNode->getEnumTypes()) {
       // The enum types array by design contains pointers to
       // MDNodes rather than DIRefs. Unique them here.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 7dbc6cb3995..d3e63e3b34f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -278,6 +278,13 @@ void DwarfExpression::AddExpression(DIExpression::expr_op_iterator I,
     case dwarf::DW_OP_deref:
       EmitOp(dwarf::DW_OP_deref);
       break;
+    case dwarf::DW_OP_constu:
+      EmitOp(dwarf::DW_OP_constu);
+      EmitUnsigned(I->getArg(0));
+      break;
+    case dwarf::DW_OP_stack_value:
+      AddStackValue();
+      break;
     default:
       llvm_unreachable("unhandled opcode found in expression");
     }