Eliminate overflow check for non-overflowing smi << operations.

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 2673 matching lines @@
                            const RangeBoundary& overflow);
 
   static RangeBoundary Sub(const RangeBoundary& a,
                            const RangeBoundary& b,
                            const RangeBoundary& overflow);
 
   static RangeBoundary Shl(const RangeBoundary& value_boundary,
                            int64_t shift_count,
                            const RangeBoundary& overflow);
 
+  static RangeBoundary Shr(const RangeBoundary& value_boundary,
+                           intptr_t shift_count) {
+    ASSERT(value_boundary.IsConstant());
+    ASSERT(shift_count >= 0);
+    int64_t value = static_cast<int64_t>(value_boundary.ConstantValue());
+    int64_t result = value >> shift_count;
+    return RangeBoundary(result);
+  }
+
   // Attempts to calculate a + b when:
   // a is a symbol and b is a constant OR
   // a is a constant and b is a symbol
   // returns true if it succeeds, output is in result.
   static bool SymbolicAdd(const RangeBoundary& a,
                           const RangeBoundary& b,
                           RangeBoundary* result);
 
   // Attempts to calculate a - b when:
   // a is a symbol and b is a constant
@@ skipping 95 matching lines @@
   static void Sub(const Range* left_range,
                   const Range* right_range,
                   RangeBoundary* min,
                   RangeBoundary* max,
                   Definition* left_defn);
 
   static bool Mul(const Range* left_range,
                   const Range* right_range,
                   RangeBoundary* min,
                   RangeBoundary* max);
+  static void Shr(const Range* left_range,
+                  const Range* right_range,
+                  RangeBoundary* min,
+                  RangeBoundary* max);
 
   static void Shl(const Range* left_range,
                   const Range* right_range,
                   RangeBoundary* min,
                   RangeBoundary* max);
 
   static bool And(const Range* left_range,
                   const Range* right_range,
                   RangeBoundary* min,
                   RangeBoundary* max);
@@ skipping 4398 matching lines @@
 
   Value* left() const { return inputs_[0]; }
   Value* right() const { return inputs_[1]; }
 
   virtual intptr_t token_pos() const { return token_pos_; }
   Token::Kind op_kind() const { return op_kind_; }
 
   void set_overflow(bool overflow) { overflow_ = overflow; }
 
   void set_is_truncating(bool value) { is_truncating_ = value; }
-  bool is_truncating() const { return is_truncating_; }
+  bool IsTruncating() const { return is_truncating_ || !overflow_; }
 
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
   DECLARE_INSTRUCTION(BinarySmiOp)
   virtual CompileType ComputeType() const;
 
   virtual bool CanDeoptimize() const;
 
   virtual bool AllowsCSE() const { return true; }
   virtual EffectSet Effects() const { return EffectSet::None(); }
@@ skipping 942 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_