Improve SHR by using range information for the shift count.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 1309 matching lines @@
   return (op_kind() == Token::kSHL) ? kDynamicCid : kSmiCid;
 }
 
 
 bool BinarySmiOpInstr::CanDeoptimize() const {
   switch (op_kind()) {
     case Token::kBIT_AND:
     case Token::kBIT_OR:
     case Token::kBIT_XOR:
       return false;
+    case Token::kSHR: {
+      // Can't deopt if shift-count is known positive.
+      Range* right_range = this->right()->definition()->range();
+      return (right_range == NULL)
+          || !right_range->IsWithin(0, RangeBoundary::kPlusInfinity);
+    }
     default:
       return overflow_;
   }
 }
 
 
 RawAbstractType* BinaryMintOpInstr::CompileType() const {
   return Type::IntType();
 }
 
@@ skipping 1156 matching lines @@
   Definition* left_defn = left()->definition();
 
   Range* left_range = left_defn->range();
   Range* right_range = right()->definition()->range();
 
   if ((left_range == NULL) || (right_range == NULL)) {
     range_ = new Range(RangeBoundary::MinSmi(), RangeBoundary::MaxSmi());
     return;
   }
 
-
-  // If left is a l
   RangeBoundary left_min =
     IsArrayLength(left_defn) ?
         RangeBoundary::FromDefinition(left_defn) : left_range->min();
 
   RangeBoundary left_max =
     IsArrayLength(left_defn) ?
         RangeBoundary::FromDefinition(left_defn) : left_range->max();
 
   RangeBoundary min;
   RangeBoundary max;
@@ skipping 125 matching lines @@
       return Array::length_offset();
     default:
       UNREACHABLE();
       return -1;
   }
 }
 
 #undef __
 
 }  // namespace dart