Recognize pattern (a << b) & c with c being a positive Smi and allow left shift to truncate the res…

runtime/vm/intermediate_language.cc

 // 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.
 
 #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 48 matching lines @@
   }
   return AttributesEqual(other);
 }
 
 
 bool Value::Equals(Value* other) const {
   return definition() == other->definition();
 }
 
 
-
 CheckClassInstr::CheckClassInstr(Value* value,
                                  intptr_t deopt_id,
                                  const ICData& unary_checks)
     : unary_checks_(unary_checks) {
   ASSERT(value != NULL);
   ASSERT(unary_checks.IsZoneHandle());
   // Expected useful check data.
   ASSERT(!unary_checks_.IsNull() &&
          (unary_checks_.NumberOfChecks() > 0) &&
          (unary_checks_.num_args_tested() == 1));
@@ skipping 51 matching lines @@
   StrictCompareInstr* other_op = other->AsStrictCompare();
   ASSERT(other_op != NULL);
   return kind() == other_op->kind();
 }
 
 
 bool BinarySmiOpInstr::AttributesEqual(Instruction* other) const {
   BinarySmiOpInstr* other_op = other->AsBinarySmiOp();
   ASSERT(other_op != NULL);
   return (op_kind() == other_op->op_kind()) &&
-      (overflow_ == other_op->overflow_);
+      (overflow_ == other_op->overflow_) &&
+      (is_truncating_ == other_op->is_truncating_);
 }
 
 
 bool LoadFieldInstr::AttributesEqual(Instruction* other) const {
   LoadFieldInstr* other_load = other->AsLoadField();
   ASSERT(other_load != NULL);
   ASSERT((offset_in_bytes() != other_load->offset_in_bytes()) ||
          ((immutable_ == other_load->immutable_)));
   return offset_in_bytes() == other_load->offset_in_bytes();
 }
@@ skipping 691 matching lines @@
     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);
     }
+    case Token::kSHL: {
+      Range* right_range = this->right()->definition()->range();
+      if ((right_range != NULL) && is_truncating()) {
+        // Can deoptimize if right can be negative.
+        return !right_range->IsWithin(0, RangeBoundary::kPlusInfinity);
+      }
+      return true;
+    }
     default:
       return overflow_;
   }
 }
 
 
 bool BinarySmiOpInstr::RightIsPowerOfTwoConstant() const {
   if (!right()->definition()->IsConstant()) return false;
   const Object& constant = right()->definition()->AsConstant()->value();
   if (!constant.IsSmi()) return false;
@@ skipping 1338 matching lines @@
     default:
       UNREACHABLE();
   }
   return kPowRuntimeEntry;
 }
 
 
 #undef __
 
 }  // namespace dart