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diff --git a/include/llvm/CodeGen/LexicalScopes.h b/include/llvm/CodeGen/LexicalScopes.h
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+++ b/include/llvm/CodeGen/LexicalScopes.h
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+//===- LexicalScopes.cpp - Collecting lexical scope info -*- C++ -*--------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements LexicalScopes analysis.
+//
+// This pass collects lexical scope information and maps machine instructions
+// to respective lexical scopes.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_LEXICALSCOPES_H
+#define LLVM_CODEGEN_LEXICALSCOPES_H
+
+#include "llvm/Metadata.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/DebugLoc.h"
+#include "llvm/Support/ValueHandle.h"
+#include <utility>
+namespace llvm {
+
+class MachineInstr;
+class MachineBasicBlock;
+class MachineFunction;
+class LexicalScope;
+
+//===----------------------------------------------------------------------===//
+/// InsnRange - This is used to track range of instructions with identical
+/// lexical scope.
+///
+typedef std::pair<const MachineInstr *, const MachineInstr *> InsnRange;
+
+//===----------------------------------------------------------------------===//
+/// LexicalScopes -  This class provides interface to collect and use lexical
+/// scoping information from machine instruction.
+///
+class LexicalScopes {
+public:
+  LexicalScopes() : MF(NULL),  CurrentFnLexicalScope(NULL) { }
+  virtual ~LexicalScopes();
+
+  /// initialize - Scan machine function and constuct lexical scope nest.
+  virtual void initialize(const MachineFunction &);
+
+  /// releaseMemory - release memory.
+  virtual void releaseMemory();
+  
+  /// empty - Return true if there is any lexical scope information available.
+  bool empty() { return CurrentFnLexicalScope == NULL; }
+
+  /// isCurrentFunctionScope - Return true if given lexical scope represents 
+  /// current function.
+  bool isCurrentFunctionScope(const LexicalScope *LS) { 
+    return LS == CurrentFnLexicalScope;
+  }
+
+  /// getCurrentFunctionScope - Return lexical scope for the current function.
+  LexicalScope *getCurrentFunctionScope() const { return CurrentFnLexicalScope;}
+
+  /// getMachineBasicBlocks - Populate given set using machine basic blocks
+  /// which have machine instructions that belong to lexical scope identified by
+  /// DebugLoc.
+  void getMachineBasicBlocks(DebugLoc DL,
+                             SmallPtrSet<const MachineBasicBlock*, 4> &MBBs);
+
+  /// dominates - Return true if DebugLoc's lexical scope dominates at least one
+  /// machine instruction's lexical scope in a given machine basic block.
+  bool dominates(DebugLoc DL, MachineBasicBlock *MBB);
+
+  /// findLexicalScope - Find lexical scope, either regular or inlined, for the
+  /// given DebugLoc. Return NULL if not found.
+  LexicalScope *findLexicalScope(DebugLoc DL);
+
+  /// getAbstractScopesList - Return a reference to list of abstract scopes.
+  ArrayRef<LexicalScope *> getAbstractScopesList() const {
+    return AbstractScopesList;
+  }
+
+  /// findAbstractScope - Find an abstract scope or return NULL.
+  LexicalScope *findAbstractScope(const MDNode *N) {
+    return AbstractScopeMap.lookup(N);
+  }
+
+  /// findInlinedScope - Find an inlined scope for the given DebugLoc or return
+  /// NULL.
+  LexicalScope *findInlinedScope(DebugLoc DL) {
+    return InlinedLexicalScopeMap.lookup(DL);
+  }
+
+  /// findLexicalScope - Find regular lexical scope or return NULL.
+  LexicalScope *findLexicalScope(const MDNode *N) {
+    return LexicalScopeMap.lookup(N);
+  }
+
+  /// dump - Print data structures to dbgs().
+  void dump();
+
+private:
+
+  /// getOrCreateLexicalScope - Find lexical scope for the given DebugLoc. If
+  /// not available then create new lexical scope.
+  LexicalScope *getOrCreateLexicalScope(DebugLoc DL);
+
+  /// getOrCreateRegularScope - Find or create a regular lexical scope.
+  LexicalScope *getOrCreateRegularScope(MDNode *Scope);
+
+  /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
+  LexicalScope *getOrCreateInlinedScope(MDNode *Scope, MDNode *InlinedAt);
+
+  /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
+  LexicalScope *getOrCreateAbstractScope(const MDNode *N);
+
+  /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
+  /// for the given machine function.
+  void extractLexicalScopes(SmallVectorImpl<InsnRange> &MIRanges,
+                            DenseMap<const MachineInstr *, LexicalScope *> &M);
+  void constructScopeNest(LexicalScope *Scope);
+  void assignInstructionRanges(SmallVectorImpl<InsnRange> &MIRanges,
+                             DenseMap<const MachineInstr *, LexicalScope *> &M);
+
+private:
+  const MachineFunction *MF;
+
+  /// LexicalScopeMap - Tracks the scopes in the current function.  Owns the
+  /// contained LexicalScope*s.
+  DenseMap<const MDNode *, LexicalScope *> LexicalScopeMap;
+
+  /// InlinedLexicalScopeMap - Tracks inlined function scopes in current function.
+  DenseMap<DebugLoc, LexicalScope *> InlinedLexicalScopeMap;
+
+  /// AbstractScopeMap - These scopes are  not included LexicalScopeMap.  
+  /// AbstractScopes owns its LexicalScope*s.
+  DenseMap<const MDNode *, LexicalScope *> AbstractScopeMap;
+
+  /// AbstractScopesList - Tracks abstract scopes constructed while processing
+  /// a function. 
+  SmallVector<LexicalScope *, 4>AbstractScopesList;
+
+  /// CurrentFnLexicalScope - Top level scope for the current function.
+  ///
+  LexicalScope *CurrentFnLexicalScope;
+};
+
+//===----------------------------------------------------------------------===//
+/// LexicalScope - This class is used to track scope information.
+///
+class LexicalScope {
+
+public:
+  LexicalScope(LexicalScope *P, const MDNode *D, const MDNode *I, bool A)
+    : Parent(P), Desc(D), InlinedAtLocation(I), AbstractScope(A),
+      LastInsn(0), FirstInsn(0), DFSIn(0), DFSOut(0), IndentLevel(0) {
+    if (Parent)
+      Parent->addChild(this);
+  }
+
+  virtual ~LexicalScope() {}
+
+  // Accessors.
+  LexicalScope *getParent() const               { return Parent; }
+  const MDNode *getDesc() const                 { return Desc; }
+  const MDNode *getInlinedAt() const            { return InlinedAtLocation; }
+  const MDNode *getScopeNode() const            { return Desc; }
+  bool isAbstractScope() const                  { return AbstractScope; }
+  SmallVector<LexicalScope *, 4> &getChildren() { return Children; }
+  SmallVector<InsnRange, 4> &getRanges()        { return Ranges; }
+
+  /// addChild - Add a child scope.
+  void addChild(LexicalScope *S) { Children.push_back(S); }
+
+  /// openInsnRange - This scope covers instruction range starting from MI.
+  void openInsnRange(const MachineInstr *MI) {
+    if (!FirstInsn)
+      FirstInsn = MI;
+
+    if (Parent)
+      Parent->openInsnRange(MI);
+  }
+
+  /// extendInsnRange - Extend the current instruction range covered by
+  /// this scope.
+  void extendInsnRange(const MachineInstr *MI) {
+    assert (FirstInsn && "MI Range is not open!");
+    LastInsn = MI;
+    if (Parent)
+      Parent->extendInsnRange(MI);
+  }
+
+  /// closeInsnRange - Create a range based on FirstInsn and LastInsn collected
+  /// until now. This is used when a new scope is encountered while walking
+  /// machine instructions.
+  void closeInsnRange(LexicalScope *NewScope = NULL) {
+    assert (LastInsn && "Last insn missing!");
+    Ranges.push_back(InsnRange(FirstInsn, LastInsn));
+    FirstInsn = NULL;
+    LastInsn = NULL;
+    // If Parent dominates NewScope then do not close Parent's instruction
+    // range.
+    if (Parent && (!NewScope || !Parent->dominates(NewScope)))
+      Parent->closeInsnRange(NewScope);
+  }
+
+  /// dominates - Return true if current scope dominsates given lexical scope.
+  bool dominates(const LexicalScope *S) const {
+    if (S == this)
+      return true;
+    if (DFSIn < S->getDFSIn() && DFSOut > S->getDFSOut())
+      return true;
+    return false;
+  }
+
+  // Depth First Search support to walk and manipulate LexicalScope hierarchy.
+  unsigned getDFSOut() const            { return DFSOut; }
+  void setDFSOut(unsigned O)            { DFSOut = O; }
+  unsigned getDFSIn() const             { return DFSIn; }
+  void setDFSIn(unsigned I)             { DFSIn = I; }
+
+  /// dump - print lexical scope.
+  void dump() const;
+
+private:
+  LexicalScope *Parent;                          // Parent to this scope.
+  AssertingVH<const MDNode> Desc;                // Debug info descriptor.
+  AssertingVH<const MDNode> InlinedAtLocation;   // Location at which this 
+                                                 // scope is inlined.
+  bool AbstractScope;                            // Abstract Scope
+  SmallVector<LexicalScope *, 4> Children;       // Scopes defined in scope.  
+                                                 // Contents not owned.
+  SmallVector<InsnRange, 4> Ranges;
+
+  const MachineInstr *LastInsn;       // Last instruction of this scope.
+  const MachineInstr *FirstInsn;      // First instruction of this scope.
+  unsigned DFSIn, DFSOut;             // In & Out Depth use to determine
+                                      // scope nesting.
+  mutable unsigned IndentLevel;       // Private state for dump()
+};
+
+} // end llvm namespace
+
+#endif