Use range analysis to improve constant propagation.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 1807 matching lines @@
   // successor.
   void set_constrained_type(ConstrainedCompileType* type) {
     constrained_type_ = type;
   }
 
   // Return compile type constrained by the comparison of this branch.
   ConstrainedCompileType* constrained_type() const {
     return constrained_type_;
   }
 
+  void set_constant_target(TargetEntryInstr* target) {
+    ASSERT(target == true_successor() || target == false_successor());
+    constant_target_ = target;
+  }
+  TargetEntryInstr* constant_target() const {
+    return constant_target_;
+  }
+
  private:
   virtual void RawSetInputAt(intptr_t i, Value* value);
 
   ComparisonInstr* comparison_;
   const bool is_checked_;
 
   ConstrainedCompileType* constrained_type_;
 
+  TargetEntryInstr* constant_target_;
+
   DISALLOW_COPY_AND_ASSIGN(BranchInstr);
 };
 
 
 class StoreContextInstr : public TemplateInstruction<1> {
  public:
   explicit StoreContextInstr(Value* value) {
     SetInputAt(0, value);
   }
 
@@ skipping 176 matching lines @@
   void PrintTo(BufferFormatter* f) const;
   static const char* ToCString(Range* range);
 
   const RangeBoundary& min() const { return min_; }
   const RangeBoundary& max() const { return max_; }
 
   bool Equals(Range* other) {
     return min_.Equals(other->min_) && max_.Equals(other->max_);
   }
 
-  static RangeBoundary ConstantMin(Range* range) {
+  static RangeBoundary ConstantMin(const Range* range) {
     if (range == NULL) return RangeBoundary::MinSmi();
     return range->min().LowerBound().Clamp();
   }
 
-  static RangeBoundary ConstantMax(Range* range) {
+  static RangeBoundary ConstantMax(const Range* range) {
     if (range == NULL) return RangeBoundary::MaxSmi();
     return range->max().UpperBound().Clamp();
   }
 
   // Inclusive.
   bool IsWithin(intptr_t min_int, intptr_t max_int) const;
 
+  bool IsUnsatisfiable() const;
+
  private:
   RangeBoundary min_;
   RangeBoundary max_;
 };
 
 
 class ConstraintInstr : public TemplateDefinition<2> {
  public:
   ConstraintInstr(Value* value, Range* constraint)
-      : constraint_(constraint) {
+      : constraint_(constraint),
+        target_(NULL) {
     SetInputAt(0, value);
   }
 
   DECLARE_INSTRUCTION(Constraint)
 
   virtual intptr_t InputCount() const {
     return (inputs_[1] == NULL) ? 1 : 2;
   }
 
   virtual CompileType ComputeType() const;
@@ skipping 13 matching lines @@
   Range* constraint() const { return constraint_; }
 
   virtual void InferRange();
 
   void AddDependency(Definition* defn) {
     Value* val = new Value(defn);
     defn->AddInputUse(val);
     SetInputAt(1, val);
   }
 
+  // Constraints for branches have their target block stored in order
+  // to find the the comparsion that generated the constraint:
+  // target->predecessor->last_instruction->comparison.
+  void set_target(TargetEntryInstr* target) {
+    target_ = target;
+  }
+  TargetEntryInstr* target() const {
+    return target_;
+  }
+
  private:
   Value* dependency() {
     return inputs_[1];
   }
 
   Range* constraint_;
+  TargetEntryInstr* target_;
 
   DISALLOW_COPY_AND_ASSIGN(ConstraintInstr);
 };
 
 
 class ConstantInstr : public TemplateDefinition<0> {
  public:
   explicit ConstantInstr(const Object& value)
       : value_(value) { }
 
@@ skipping 2573 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_