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

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 223 matching lines @@
 
   Definition* definition() const { return definition_; }
   void set_definition(Definition* definition) { definition_ = definition; }
 
   Value* previous_use() const { return previous_use_; }
   void set_previous_use(Value* previous) { previous_use_ = previous; }
 
   Value* next_use() const { return next_use_; }
   void set_next_use(Value* next) { next_use_ = next; }
 
+  bool IsSingleUse() const {
+    return (next_use_ == NULL) && (previous_use_ == NULL);

[Florian Schneider, 2013/02/21 10:30:47]

We have env_use_list to keep track of environment uses, so checking if the
definition has exactly one input use (and no environment uses) can be done
using:

return next_use_ == NULL
    && previous_use_ == NULL
    && definition_->env_use_list() == NULL;

[Kevin Millikin (Google), 2013/02/21 12:44:35]

Drive by to the drive by.  I think it's more natural to just write:

return (definition()->input_use_list() == this) &&
  (next_use() == NULL) &&
  (definition()->env_use_list() == NULL);

Both your definition and the original answer true for use list nodes held in
instructions that have been removed from the graph, which just seems like a
strange behavior.

[srdjan, 2013/02/21 15:56:27]

We remove environment use list lazily in register allocator, i.e., env_use_list
is most of the time non-null.

+  }
+
   Instruction* instruction() const { return instruction_; }
   void set_instruction(Instruction* instruction) { instruction_ = instruction; }
 
   intptr_t use_index() const { return use_index_; }
   void set_use_index(intptr_t index) { use_index_ = index; }
 
   static void AddToList(Value* value, Value** list);
   void RemoveFromUseList();
 
   Value* Copy() { return new Value(definition_); }
@@ skipping 3412 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(BinaryDoubleOpInstr);
 };
 
 
 class BinaryMintOpInstr : public TemplateDefinition<2> {
  public:
   BinaryMintOpInstr(Token::Kind op_kind,
                            Value* left,
                            Value* right,
                            InstanceCallInstr* instance_call)
-      : op_kind_(op_kind) {
+      : op_kind_(op_kind),
+        instance_call_(instance_call) {
     ASSERT(left != NULL);
     ASSERT(right != NULL);
     inputs_[0] = left;
     inputs_[1] = right;
     deopt_id_ = instance_call->deopt_id();
   }
 
   Value* left() const { return inputs_[0]; }
   Value* right() const { return inputs_[1]; }
 
   Token::Kind op_kind() const { return op_kind_; }
 
+  InstanceCallInstr* instance_call() const { return instance_call_; }
+
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
   virtual bool CanDeoptimize() const {
     return (op_kind() == Token::kADD) || (op_kind() == Token::kSUB);
   }
 
   virtual bool HasSideEffect() const { return false; }
 
   virtual bool AffectedBySideEffect() const { return false; }
 
   virtual bool AttributesEqual(Instruction* other) const {
+    ASSERT(other->IsBinaryMintOp());
     return op_kind() == other->AsBinaryMintOp()->op_kind();
   }
 
   virtual CompileType* ComputeInitialType() const;
 
   virtual Representation representation() const {
     return kUnboxedMint;
   }
 
   virtual Representation RequiredInputRepresentation(intptr_t idx) const {
     ASSERT((idx == 0) || (idx == 1));
     return kUnboxedMint;
   }
 
   virtual intptr_t DeoptimizationTarget() const {
     // Direct access since this instruction cannot deoptimize, and the deopt-id
     // was inherited from another instruction that could deoptimize.
     return deopt_id_;
   }
 
   virtual Definition* Canonicalize(FlowGraphOptimizer* optimizer);
 
   DECLARE_INSTRUCTION(BinaryMintOp)
 
  private:
   const Token::Kind op_kind_;
+  InstanceCallInstr* instance_call_;
 
   DISALLOW_COPY_AND_ASSIGN(BinaryMintOpInstr);
 };
 
 
 class ShiftMintOpInstr : public TemplateDefinition<2> {
  public:
   ShiftMintOpInstr(Token::Kind op_kind,
                    Value* left,
                    Value* right,
@@ skipping 105 matching lines @@
 
 
 class BinarySmiOpInstr : public TemplateDefinition<2> {
  public:
   BinarySmiOpInstr(Token::Kind op_kind,
                    InstanceCallInstr* instance_call,
                    Value* left,
                    Value* right)
       : op_kind_(op_kind),
         instance_call_(instance_call),
-        overflow_(true) {
+        overflow_(true),
+        is_truncating_(false) {
     ASSERT(left != NULL);
     ASSERT(right != NULL);
     inputs_[0] = left;
     inputs_[1] = right;
     deopt_id_ = instance_call->deopt_id();
   }
 
   Value* left() const { return inputs_[0]; }
   Value* right() const { return inputs_[1]; }
 
@@ skipping 13 matching lines @@
 
   virtual bool HasSideEffect() const { return false; }
 
   virtual bool AffectedBySideEffect() const { return false; }
   virtual bool AttributesEqual(Instruction* other) const;
 
   void set_overflow(bool overflow) {
     overflow_ = overflow;
   }
 
+  void set_is_truncating(bool value) {
+    is_truncating_ = value;
+  }
+  bool is_truncating() const { return is_truncating_; }
+
   void PrintTo(BufferFormatter* f) const;
 
   virtual void InferRange();
 
   virtual Definition* Canonicalize(FlowGraphOptimizer* optimizer);
 
   // Returns true if right is a non-zero Smi constant which absolute value is
   // a power of two.
   bool RightIsPowerOfTwoConstant() const;
 
  private:
   const Token::Kind op_kind_;
   InstanceCallInstr* instance_call_;
   bool overflow_;
+  bool is_truncating_;
 
   DISALLOW_COPY_AND_ASSIGN(BinarySmiOpInstr);
 };
 
 
 // Handles both Smi operations: BIT_OR and NEGATE.
 class UnarySmiOpInstr : public TemplateDefinition<1> {
  public:
   UnarySmiOpInstr(Token::Kind op_kind,
                   InstanceCallInstr* instance_call,
@@ skipping 565 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_