2 files changed, 178 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 89a7974e473..5a413bed920 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -365,15 +365,15 @@ unsigned CodeViewDebug::getPointerSizeInBytes() {
 }
 
 void CodeViewDebug::recordLocalVariable(LocalVariable &&Var,
-                                        const DILocation *InlinedAt) {
-  if (InlinedAt) {
+                                        const LexicalScope *LS) {
+  if (const DILocation *InlinedAt = LS->getInlinedAt()) {
     // This variable was inlined. Associate it with the InlineSite.
     const DISubprogram *Inlinee = Var.DIVar->getScope()->getSubprogram();
     InlineSite &Site = getInlineSite(InlinedAt, Inlinee);
     Site.InlinedLocals.emplace_back(Var);
   } else {
-    // This variable goes in the main ProcSym.
-    CurFn->Locals.emplace_back(Var);
+    // This variable goes into the corresponding lexical scope.
+    ScopeVariables[LS].emplace_back(Var);
   }
 }
 
@@ -905,6 +905,7 @@ void CodeViewDebug::emitDebugInfoForFunction(const Function *GV,
     OS.EmitLabel(ProcRecordEnd);
 
     emitLocalVariableList(FI.Locals);
+    emitLexicalBlockList(FI.ChildBlocks, FI);
 
     // Emit inlined call site information. Only emit functions inlined directly
     // into the parent function. We'll emit the other sites recursively as part
@@ -1025,7 +1026,7 @@ void CodeViewDebug::collectVariableInfoFromMFTable(
     LocalVariable Var;
     Var.DIVar = VI.Var;
     Var.DefRanges.emplace_back(std::move(DefRange));
-    recordLocalVariable(std::move(Var), VI.Loc->getInlinedAt());
+    recordLocalVariable(std::move(Var), Scope);
   }
 }
 
@@ -1156,7 +1157,7 @@ void CodeViewDebug::collectVariableInfo(const DISubprogram *SP) {
     Var.DIVar = DIVar;
 
     calculateRanges(Var, Ranges);
-    recordLocalVariable(std::move(Var), InlinedAt);
+    recordLocalVariable(std::move(Var), Scope);
   }
 }
 
@@ -2363,6 +2364,131 @@ void CodeViewDebug::emitLocalVariable(const LocalVariable &Var) {
   }
 }
 
+void CodeViewDebug::emitLexicalBlockList(ArrayRef<LexicalBlock *> Blocks,
+                                         const FunctionInfo& FI) {
+  for (LexicalBlock *Block : Blocks)
+    emitLexicalBlock(*Block, FI);
+}
+
+/// Emit an S_BLOCK32 and S_END record pair delimiting the contents of a
+/// lexical block scope.
+void CodeViewDebug::emitLexicalBlock(const LexicalBlock &Block,
+                                     const FunctionInfo& FI) {
+  MCSymbol *RecordBegin = MMI->getContext().createTempSymbol(),
+           *RecordEnd   = MMI->getContext().createTempSymbol();
+
+  // Lexical block symbol record.
+  OS.AddComment("Record length");
+  OS.emitAbsoluteSymbolDiff(RecordEnd, RecordBegin, 2);   // Record Length
+  OS.EmitLabel(RecordBegin);
+  OS.AddComment("Record kind: S_BLOCK32");
+  OS.EmitIntValue(SymbolKind::S_BLOCK32, 2);              // Record Kind
+  OS.AddComment("PtrParent");
+  OS.EmitIntValue(0, 4);                                  // PtrParent
+  OS.AddComment("PtrEnd");
+  OS.EmitIntValue(0, 4);                                  // PtrEnd
+  OS.AddComment("Code size");
+  OS.emitAbsoluteSymbolDiff(Block.End, Block.Begin, 4);   // Code Size
+  OS.AddComment("Function section relative address");
+  OS.EmitCOFFSecRel32(Block.Begin, /*Offset=*/0);         // Func Offset
+  OS.AddComment("Function section index");
+  OS.EmitCOFFSectionIndex(FI.Begin);                      // Func Symbol
+  OS.AddComment("Lexical block name");
+  emitNullTerminatedSymbolName(OS, Block.Name);           // Name
+  OS.EmitLabel(RecordEnd);
+
+  // Emit variables local to this lexical block.
+  emitLocalVariableList(Block.Locals);
+
+  // Emit lexical blocks contained within this block.
+  emitLexicalBlockList(Block.Children, FI);
+
+  // Close the lexical block scope.
+  OS.AddComment("Record length");
+  OS.EmitIntValue(2, 2);                                  // Record Length
+  OS.AddComment("Record kind: S_END");
+  OS.EmitIntValue(SymbolKind::S_END, 2);                  // Record Kind
+}
+
+/// Convenience routine for collecting lexical block information for a list
+/// of lexical scopes.
+void CodeViewDebug::collectLexicalBlockInfo(
+        SmallVectorImpl<LexicalScope *> &Scopes,
+        SmallVectorImpl<LexicalBlock *> &Blocks,
+        SmallVectorImpl<LocalVariable> &Locals) {
+  for (LexicalScope *Scope : Scopes)
+    collectLexicalBlockInfo(*Scope, Blocks, Locals);
+}
+
+/// Populate the lexical blocks and local variable lists of the parent with
+/// information about the specified lexical scope.
+void CodeViewDebug::collectLexicalBlockInfo(
+    LexicalScope &Scope,
+    SmallVectorImpl<LexicalBlock *> &ParentBlocks,
+    SmallVectorImpl<LocalVariable> &ParentLocals) {
+  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;
+
+  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);
+    return;
+  }
+
+  // Create a new CodeView lexical block for this lexical scope.  If we've
+  // seen this DILexicalBlock before then the scope tree is malformed and
+  // we can handle this gracefully by not processing it a second time.
+  auto BlockInsertion = CurFn->LexicalBlocks.insert({DILB, LexicalBlock()});
+  if (!BlockInsertion.second)
+    return;
+
+  // Create a lexical block containing the local 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;
+  Block.Begin = getLabelBeforeInsn(Range.first);
+  Block.End = getLabelAfterInsn(Range.second);
+  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);
+  ParentBlocks.push_back(&Block);
+  collectLexicalBlockInfo(Scope.getChildren(), Block.Children, Block.Locals);
+}
+
 void CodeViewDebug::endFunctionImpl(const MachineFunction *MF) {
   const Function &GV = MF->getFunction();
   assert(FnDebugInfo.count(&GV));
@@ -2370,6 +2496,15 @@ void CodeViewDebug::endFunctionImpl(const MachineFunction *MF) {
 
   collectVariableInfo(GV.getSubprogram());
 
+  // Build the lexical block structure to emit for this routine.
+  if (LexicalScope *CFS = LScopes.getCurrentFunctionScope())
+    collectLexicalBlockInfo(*CFS, CurFn->ChildBlocks, CurFn->Locals);
+
+  // Clear the scope and variable information from the map which will not be
+  // valid after we have finished processing this routine.  This also prepares
+  // the map for the subsequent routine.
+  ScopeVariables.clear();
+
   // Don't emit anything if we don't have any line tables.
   if (!CurFn->HaveLineInfo) {
     FnDebugInfo.erase(&GV);
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index 0833d217555..236a70ef15d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -107,6 +107,15 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
     unsigned SiteFuncId = 0;
   };
 
+  // Combines information from DILexicalBlock and LexicalScope.
+  struct LexicalBlock {
+    SmallVector<LocalVariable, 1> Locals;
+    SmallVector<LexicalBlock *, 1> Children;
+    const MCSymbol *Begin;
+    const MCSymbol *End;
+    StringRef Name;
+  };
+
   // For each function, store a vector of labels to its instructions, as well as
   // to the end of the function.
   struct FunctionInfo {
@@ -124,6 +133,11 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
     SmallVector<LocalVariable, 1> Locals;
 
+    std::unordered_map<const DILexicalBlockBase*, LexicalBlock> LexicalBlocks;
+
+    // Lexical blocks containing local variables.
+    SmallVector<LexicalBlock *, 1> ChildBlocks;
+
     std::vector<std::pair<MCSymbol *, MDNode *>> Annotations;
 
     const MCSymbol *Begin = nullptr;
@@ -134,6 +148,12 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
   };
   FunctionInfo *CurFn = nullptr;
 
+  // Map used to seperate variables according to the lexical scope they belong
+  // in.  This is populated by recordLocalVariable() before
+  // collectLexicalBlocks() separates the variables between the FunctionInfo
+  // and LexicalBlocks.
+  DenseMap<const LexicalScope *, SmallVector<LocalVariable, 1>> ScopeVariables;
+
   /// The set of comdat .debug$S sections that we've seen so far. Each section
   /// must start with a magic version number that must only be emitted once.
   /// This set tracks which sections we've already opened.
@@ -258,9 +278,18 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
   void collectVariableInfoFromMFTable(DenseSet<InlinedVariable> &Processed);
 
+  // Construct the lexical block tree for a routine, pruning emptpy lexical
+  // scopes, and populate it with local variables.
+  void collectLexicalBlockInfo(SmallVectorImpl<LexicalScope *> &Scopes,
+                               SmallVectorImpl<LexicalBlock *> &Blocks,
+                               SmallVectorImpl<LocalVariable> &Locals);
+  void collectLexicalBlockInfo(LexicalScope &Scope,
+                               SmallVectorImpl<LexicalBlock *> &ParentBlocks,
+                               SmallVectorImpl<LocalVariable> &ParentLocals);
+
   /// Records information about a local variable in the appropriate scope. In
   /// particular, locals from inlined code live inside the inlining site.
-  void recordLocalVariable(LocalVariable &&Var, const DILocation *Loc);
+  void recordLocalVariable(LocalVariable &&Var, const LexicalScope *LS);
 
   /// Emits local variables in the appropriate order.
   void emitLocalVariableList(ArrayRef<LocalVariable> Locals);
@@ -268,6 +297,13 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
   /// Emits an S_LOCAL record and its associated defined ranges.
   void emitLocalVariable(const LocalVariable &Var);
 
+  /// Emits a sequence of lexical block scopes and their children.
+  void emitLexicalBlockList(ArrayRef<LexicalBlock *> Blocks,
+                            const FunctionInfo& FI);
+
+  /// Emit a lexical block scope and its children.
+  void emitLexicalBlock(const LexicalBlock &Block, const FunctionInfo& FI);
+
   /// Translates the DIType to codeview if necessary and returns a type index
   /// for it.
   codeview::TypeIndex getTypeIndex(DITypeRef TypeRef,