Improve and simplify removal of unreachable code

src/lithium-codegen.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#ifndef V8_TYPING_H_
-#define V8_TYPING_H_
+#ifndef V8_LITHIUM_CODEGEN_H_
+#define V8_LITHIUM_CODEGEN_H_
 
 #include "v8.h"
 
-#include "allocation.h"
-#include "ast.h"
 #include "compiler.h"
-#include "type-info.h"
-#include "types.h"
-#include "effects.h"
-#include "zone.h"
-#include "scopes.h"
 
 namespace v8 {
 namespace internal {
 
+class LInstruction;
+class LPlatformChunk;
 
-class AstTyper: public AstVisitor {
+class LCodeGenBase BASE_EMBEDDED {
  public:
-  static void Run(CompilationInfo* info);
+  LCodeGenBase(LChunk* chunk,
+               MacroAssembler* assembler,
+               CompilationInfo* info);
+  virtual ~LCodeGenBase() {}
 
-  void* operator new(size_t size, Zone* zone) {
-    return zone->New(static_cast<int>(size));
-  }
-  void operator delete(void* pointer, Zone* zone) { }
-  void operator delete(void* pointer) { }
+  // Simple accessors.
+  MacroAssembler* masm() const { return masm_; }
+  CompilationInfo* info() const { return info_; }
+  Isolate* isolate() const { return info_->isolate(); }
+  Factory* factory() const { return isolate()->factory(); }
+  Heap* heap() const { return isolate()->heap(); }
+  Zone* zone() const { return zone_; }
+  LPlatformChunk* chunk() const { return chunk_; }
+  HGraph* graph() const;
 
-  DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
+  void FPRINTF_CHECKING Comment(const char* format, ...);
 
- private:
-  explicit AstTyper(CompilationInfo* info);
+  bool GenerateBody();
+  virtual void GenerateBodyInstructionPre(LInstruction* instr) {}
+  virtual void GenerateBodyInstructionPost(LInstruction* instr) {}
 
-  static const int kNoVar = INT_MIN;
-  typedef v8::internal::Effects<int, kNoVar> Effects;
-  typedef v8::internal::NestedEffects<int, kNoVar> Store;
+  virtual void EnsureSpaceForLazyDeopt(int space_needed) = 0;
+  virtual void RecordAndUpdatePosition(int position) = 0;
 
-  CompilationInfo* info_;
-  TypeFeedbackOracle oracle_;
-  Store store_;
+  int GetNextEmittedBlock() const;
 
-  TypeFeedbackOracle* oracle() { return &oracle_; }
-  Zone* zone() const { return info_->zone(); }
+ protected:
+  enum Status {
+    UNUSED,
+    GENERATING,
+    DONE,
+    ABORTED
+  };
 
-  void NarrowType(Expression* e, Bounds b) {
-    e->set_bounds(Bounds::Both(e->bounds(), b, isolate_));
-  }
-  void NarrowLowerType(Expression* e, Handle<Type> t) {
-    e->set_bounds(Bounds::NarrowLower(e->bounds(), t, isolate_));
-  }
+  LPlatformChunk* const chunk_;
+  MacroAssembler* const masm_;
+  CompilationInfo* const info_;
+  Zone* zone_;
+  Status status_;
+  int current_block_;
+  int current_instruction_;
+  const ZoneList<LInstruction*>* instructions_;
+  int last_lazy_deopt_pc_;
 
-  Effects EnterEffects() {
-    store_ = store_.Push();
-    return store_.Top();
-  }
-  void ExitEffects() { store_ = store_.Pop(); }
+  bool is_unused() const { return status_ == UNUSED; }
+  bool is_generating() const { return status_ == GENERATING; }
+  bool is_done() const { return status_ == DONE; }
+  bool is_aborted() const { return status_ == ABORTED; }
+};
 
-  int variable_index(Variable* var) {
-    return var->IsStackLocal() ? var->index() :
-           var->IsParameter() ? -var->index() : kNoVar;
-  }
-
-  void VisitDeclarations(ZoneList<Declaration*>* declarations);
-  void VisitStatements(ZoneList<Statement*>* statements);
-
-#define DECLARE_VISIT(type) virtual void Visit##type(type* node);
-  AST_NODE_LIST(DECLARE_VISIT)
-#undef DECLARE_VISIT
-
-  DISALLOW_COPY_AND_ASSIGN(AstTyper);
-};
 
 } }  // namespace v8::internal
 
-#endif  // V8_TYPING_H_
+#endif  // V8_LITHIUM_CODEGEN_H_