[CodeView] Emit global variables within lexical scopes to limit visibility

Emit static locals within the correct lexical scope so variables with the same
name will not confuse the debugger into getting the wrong value.

Differential Revision: https://reviews.llvm.org/D55336

llvm-svn: 349777

1 files changed, 126 insertions, 75 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 4132b1a30c4..990f0f4670b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -124,6 +124,8 @@ CodeViewDebug::CodeViewDebug(AsmPrinter *AP)
   TheCPU =
       mapArchToCVCPUType(Triple(MMI->getModule()->getTargetTriple()).getArch());
 
+  collectGlobalVariableInfo();
+
   // Check if we should emit type record hashes.
   ConstantInt *GH = mdconst::extract_or_null<ConstantInt>(
       MMI->getModule()->getModuleFlag("CodeViewGHash"));
@@ -1038,6 +1040,7 @@ void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
     endSymbolRecord(FrameProcEnd);
 
     emitLocalVariableList(FI, FI.Locals);
+    emitGlobalVariableList(FI.Globals);
     emitLexicalBlockList(FI.ChildBlocks, FI);
 
     // Emit inlined call site information. Only emit functions inlined directly
@@ -2046,6 +2049,7 @@ void CodeViewDebug::clear() {
   GlobalUDTs.clear();
   TypeIndices.clear();
   CompleteTypeIndices.clear();
+  ScopeGlobals.clear();
 }
 
 void CodeViewDebug::collectMemberInfo(ClassInfo &Info,
@@ -2648,6 +2652,7 @@ void CodeViewDebug::emitLexicalBlock(const LexicalBlock &Block,
 
   // Emit variables local to this lexical block.
   emitLocalVariableList(FI, Block.Locals);
+  emitGlobalVariableList(Block.Globals);
 
   // Emit lexical blocks contained within this block.
   emitLexicalBlockList(Block.Children, FI);
@@ -2661,9 +2666,10 @@ void CodeViewDebug::emitLexicalBlock(const LexicalBlock &Block,
 void CodeViewDebug::collectLexicalBlockInfo(
         SmallVectorImpl<LexicalScope *> &Scopes,
         SmallVectorImpl<LexicalBlock *> &Blocks,
-        SmallVectorImpl<LocalVariable> &Locals) {
+        SmallVectorImpl<LocalVariable> &Locals,
+        SmallVectorImpl<CVGlobalVariable> &Globals) {
   for (LexicalScope *Scope : Scopes)
-    collectLexicalBlockInfo(*Scope, Blocks, Locals);
+    collectLexicalBlockInfo(*Scope, Blocks, Locals, Globals);
 }
 
 /// Populate the lexical blocks and local variable lists of the parent with
@@ -2671,45 +2677,58 @@ void CodeViewDebug::collectLexicalBlockInfo(
 void CodeViewDebug::collectLexicalBlockInfo(
     LexicalScope &Scope,
     SmallVectorImpl<LexicalBlock *> &ParentBlocks,
-    SmallVectorImpl<LocalVariable> &ParentLocals) {
+    SmallVectorImpl<LocalVariable> &ParentLocals,
+    SmallVectorImpl<CVGlobalVariable> &ParentGlobals) {
   if (Scope.isAbstractScope())
     return;
 
-  auto LocalsIter = ScopeVariables.find(&Scope);
-  if (LocalsIter == ScopeVariables.end()) {
-    // This scope does not contain variables and can be eliminated.
-    collectLexicalBlockInfo(Scope.getChildren(), ParentBlocks, ParentLocals);
-    return;
-  }
-  SmallVectorImpl<LocalVariable> &Locals = LocalsIter->second;
-
+  // Gather information about the lexical scope including local variables,
+  // global variables, and address ranges.
+  bool IgnoreScope = false;
+  auto LI = ScopeVariables.find(&Scope);
+  SmallVectorImpl<LocalVariable> *Locals =
+      LI != ScopeVariables.end() ? &LI->second : nullptr;
+  auto GI = ScopeGlobals.find(Scope.getScopeNode());
+  SmallVectorImpl<CVGlobalVariable> *Globals =
+      GI != ScopeGlobals.end() ? GI->second.get() : nullptr;
   const DILexicalBlock *DILB = dyn_cast<DILexicalBlock>(Scope.getScopeNode());
-  if (!DILB) {
-    // This scope is not a lexical block and can be eliminated, but keep any
-    // local variables it contains.
-    ParentLocals.append(Locals.begin(), Locals.end());
-    collectLexicalBlockInfo(Scope.getChildren(), ParentBlocks, ParentLocals);
-    return;
-  }
-
   const SmallVectorImpl<InsnRange> &Ranges = Scope.getRanges();
-  if (Ranges.size() != 1 || !getLabelAfterInsn(Ranges.front().second)) {
-    // This lexical block scope has too many address ranges to represent in the
-    // current CodeView format or does not have a valid address range.
-    // Eliminate this lexical scope and promote any locals it contains to the
-    // parent scope.
-    //
-    // For lexical scopes with multiple address ranges you may be tempted to
-    // construct a single range covering every instruction where the block is
-    // live and everything in between.  Unfortunately, Visual Studio only
-    // displays variables from the first matching lexical block scope.  If the
-    // first lexical block contains exception handling code or cold code which
-    // is moved to the bottom of the routine creating a single range covering
-    // nearly the entire routine, then it will hide all other lexical blocks
-    // and the variables they contain.
-    //
-    ParentLocals.append(Locals.begin(), Locals.end());
-    collectLexicalBlockInfo(Scope.getChildren(), ParentBlocks, ParentLocals);
+
+  // Ignore lexical scopes which do not contain variables.
+  if (!Locals && !Globals)
+    IgnoreScope = true;
+
+  // Ignore lexical scopes which are not lexical blocks.
+  if (!DILB)
+    IgnoreScope = true;
+
+  // Ignore scopes which have too many address ranges to represent in the
+  // current CodeView format or do not have a valid address range.
+  //
+  // For lexical scopes with multiple address ranges you may be tempted to
+  // construct a single range covering every instruction where the block is
+  // live and everything in between.  Unfortunately, Visual Studio only
+  // displays variables from the first matching lexical block scope.  If the
+  // first lexical block contains exception handling code or cold code which
+  // is moved to the bottom of the routine creating a single range covering
+  // nearly the entire routine, then it will hide all other lexical blocks
+  // and the variables they contain.
+  if (Ranges.size() != 1 || !getLabelAfterInsn(Ranges.front().second))
+    IgnoreScope = true;
+
+  if (IgnoreScope) {
+    // This scope can be safely ignored and eliminating it will reduce the
+    // size of the debug information. Be sure to collect any variable and scope
+    // information from the this scope or any of its children and collapse them
+    // into the parent scope.
+    if (Locals)
+      ParentLocals.append(Locals->begin(), Locals->end());
+    if (Globals)
+      ParentGlobals.append(Globals->begin(), Globals->end());
+    collectLexicalBlockInfo(Scope.getChildren(),
+                            ParentBlocks,
+                            ParentLocals,
+                            ParentGlobals);
     return;
   }
 
@@ -2720,8 +2739,8 @@ void CodeViewDebug::collectLexicalBlockInfo(
   if (!BlockInsertion.second)
     return;
 
-  // Create a lexical block containing the local variables and collect the
-  // the lexical block information for the children.
+  // Create a lexical block containing the variables and collect the the
+  // lexical block information for the children.
   const InsnRange &Range = Ranges.front();
   assert(Range.first && Range.second);
   LexicalBlock &Block = BlockInsertion.first->second;
@@ -2730,9 +2749,15 @@ void CodeViewDebug::collectLexicalBlockInfo(
   assert(Block.Begin && "missing label for scope begin");
   assert(Block.End && "missing label for scope end");
   Block.Name = DILB->getName();
-  Block.Locals = std::move(Locals);
+  if (Locals)
+    Block.Locals = std::move(*Locals);
+  if (Globals)
+    Block.Globals = std::move(*Globals);
   ParentBlocks.push_back(&Block);
-  collectLexicalBlockInfo(Scope.getChildren(), Block.Children, Block.Locals);
+  collectLexicalBlockInfo(Scope.getChildren(),
+                          Block.Children,
+                          Block.Locals,
+                          Block.Globals);
 }
 
 void CodeViewDebug::endFunctionImpl(const MachineFunction *MF) {
@@ -2744,7 +2769,10 @@ void CodeViewDebug::endFunctionImpl(const MachineFunction *MF) {
 
   // Build the lexical block structure to emit for this routine.
   if (LexicalScope *CFS = LScopes.getCurrentFunctionScope())
-    collectLexicalBlockInfo(*CFS, CurFn->ChildBlocks, CurFn->Locals);
+    collectLexicalBlockInfo(*CFS,
+                            CurFn->ChildBlocks,
+                            CurFn->Locals,
+                            CurFn->Globals);
 
   // Clear the scope and variable information from the map which will not be
   // valid after we have finished processing this routine.  This also prepares
@@ -2861,7 +2889,7 @@ void CodeViewDebug::emitDebugInfoForUDTs(
   }
 }
 
-void CodeViewDebug::emitDebugInfoForGlobals() {
+void CodeViewDebug::collectGlobalVariableInfo() {
   DenseMap<const DIGlobalVariableExpression *, const GlobalVariable *>
       GlobalMap;
   for (const GlobalVariable &GV : MMI->getModule()->globals()) {
@@ -2874,42 +2902,56 @@ void CodeViewDebug::emitDebugInfoForGlobals() {
   NamedMDNode *CUs = MMI->getModule()->getNamedMetadata("llvm.dbg.cu");
   for (const MDNode *Node : CUs->operands()) {
     const auto *CU = cast<DICompileUnit>(Node);
-
-    // First, emit all globals that are not in a comdat in a single symbol
-    // substream. MSVC doesn't like it if the substream is empty, so only open
-    // it if we have at least one global to emit.
-    switchToDebugSectionForSymbol(nullptr);
-    MCSymbol *EndLabel = nullptr;
     for (const auto *GVE : CU->getGlobalVariables()) {
-      if (const auto *GV = GlobalMap.lookup(GVE))
-        if (!GV->hasComdat() && !GV->isDeclarationForLinker()) {
-          if (!EndLabel) {
-            OS.AddComment("Symbol subsection for globals");
-            EndLabel = beginCVSubsection(DebugSubsectionKind::Symbols);
-          }
-          // FIXME: emitDebugInfoForGlobal() doesn't handle DIExpressions.
-          emitDebugInfoForGlobal(GVE->getVariable(), GV, Asm->getSymbol(GV));
-        }
+      const auto *GV = GlobalMap.lookup(GVE);
+      if (!GV || GV->isDeclarationForLinker())
+        continue;
+      const DIGlobalVariable *DIGV = GVE->getVariable();
+      DIScope *Scope = DIGV->getScope();
+      SmallVector<CVGlobalVariable, 1> *VariableList;
+      if (Scope && isa<DILocalScope>(Scope)) {
+        // Locate a global variable list for this scope, creating one if
+        // necessary.
+        auto Insertion = ScopeGlobals.insert(
+            {Scope, std::unique_ptr<GlobalVariableList>()});
+        if (Insertion.second)
+          Insertion.first->second = llvm::make_unique<GlobalVariableList>();
+        VariableList = Insertion.first->second.get();
+      } else if (GV->hasComdat())
+        // Emit this global variable into a COMDAT section.
+        VariableList = &ComdatVariables;
+      else
+        // Emit this globla variable in a single global symbol section.
+        VariableList = &GlobalVariables;
+      CVGlobalVariable CVGV = {DIGV, GV};
+      VariableList->emplace_back(std::move(CVGV));
     }
-    if (EndLabel)
-      endCVSubsection(EndLabel);
+  }
+}
 
-    // Second, emit each global that is in a comdat into its own .debug$S
-    // section along with its own symbol substream.
-    for (const auto *GVE : CU->getGlobalVariables()) {
-      if (const auto *GV = GlobalMap.lookup(GVE)) {
-        if (GV->hasComdat()) {
-          MCSymbol *GVSym = Asm->getSymbol(GV);
-          OS.AddComment("Symbol subsection for " +
-                        Twine(GlobalValue::dropLLVMManglingEscape(GV->getName())));
-          switchToDebugSectionForSymbol(GVSym);
-          EndLabel = beginCVSubsection(DebugSubsectionKind::Symbols);
-          // FIXME: emitDebugInfoForGlobal() doesn't handle DIExpressions.
-          emitDebugInfoForGlobal(GVE->getVariable(), GV, GVSym);
-          endCVSubsection(EndLabel);
-        }
-      }
-    }
+void CodeViewDebug::emitDebugInfoForGlobals() {
+  // First, emit all globals that are not in a comdat in a single symbol
+  // substream. MSVC doesn't like it if the substream is empty, so only open
+  // it if we have at least one global to emit.
+  switchToDebugSectionForSymbol(nullptr);
+  if (!GlobalVariables.empty()) {
+    OS.AddComment("Symbol subsection for globals");
+    MCSymbol *EndLabel = beginCVSubsection(DebugSubsectionKind::Symbols);
+    emitGlobalVariableList(GlobalVariables);
+    endCVSubsection(EndLabel);
+  }
+
+  // Second, emit each global that is in a comdat into its own .debug$S
+  // section along with its own symbol substream.
+  for (const CVGlobalVariable &CVGV : ComdatVariables) {
+    MCSymbol *GVSym = Asm->getSymbol(CVGV.GV);
+    OS.AddComment("Symbol subsection for " +
+            Twine(GlobalValue::dropLLVMManglingEscape(CVGV.GV->getName())));
+    switchToDebugSectionForSymbol(GVSym);
+    MCSymbol *EndLabel = beginCVSubsection(DebugSubsectionKind::Symbols);
+    // FIXME: emitDebugInfoForGlobal() doesn't handle DIExpressions.
+    emitDebugInfoForGlobal(CVGV.DIGV, CVGV.GV, GVSym);
+    endCVSubsection(EndLabel);
   }
 }
 
@@ -2925,6 +2967,15 @@ void CodeViewDebug::emitDebugInfoForRetainedTypes() {
   }
 }
 
+// Emit each global variable in the specified array.
+void CodeViewDebug::emitGlobalVariableList(ArrayRef<CVGlobalVariable> Globals) {
+  for (const CVGlobalVariable &CVGV : Globals) {
+    MCSymbol *GVSym = Asm->getSymbol(CVGV.GV);
+    // FIXME: emitDebugInfoForGlobal() doesn't handle DIExpressions.
+    emitDebugInfoForGlobal(CVGV.DIGV, CVGV.GV, GVSym);
+  }
+}
+
 void CodeViewDebug::emitDebugInfoForGlobal(const DIGlobalVariable *DIGV,
                                            const GlobalVariable *GV,
                                            MCSymbol *GVSym) {