- Canonicalize array bounds checks to avoid deopting when comparing

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 6134 matching lines @@
 };
 
 
 class CheckArrayBoundInstr : public TemplateInstruction<2> {
  public:
   CheckArrayBoundInstr(Value* length,
                        Value* index,
                        intptr_t array_type,
                        InstanceCallInstr* instance_call)
       : array_type_(array_type) {
-    SetInputAt(0, length);
-    SetInputAt(1, index);
+    SetInputAt(locLength, length);
+    SetInputAt(locIndex, index);
     deopt_id_ = instance_call->deopt_id();
   }
 
-  Value* length() const { return inputs_[0]; }
-  Value* index() const { return inputs_[1]; }
+  Value* length() const { return inputs_[locLength]; }
+  Value* index() const { return inputs_[locIndex]; }
 
   intptr_t array_type() const { return array_type_; }
 
   DECLARE_INSTRUCTION(CheckArrayBound)
 
   virtual intptr_t ArgumentCount() const { return 0; }
 
   virtual bool CanDeoptimize() const { return true; }
 
   bool IsRedundant(RangeBoundary length);
 
+  virtual Instruction* Canonicalize(FlowGraph* flow_graph);
+
   // Returns the length offset for array and string types.
   static intptr_t LengthOffsetFor(intptr_t class_id);
 
   static bool IsFixedLengthArrayType(intptr_t class_id);
 
   virtual bool AllowsCSE() const { return true; }
   virtual EffectSet Effects() const { return EffectSet::None(); }
   virtual EffectSet Dependencies() const { return EffectSet::None(); }
   virtual bool AttributesEqual(Instruction* other) const;
 
   virtual bool MayThrow() const { return false; }
 
  private:
+  // Give a name to the location/input indices.
+  enum {
+    locLength = 0,
+    locIndex = 1

[srdjan, 2013/05/14 18:11:47]

Optional: prefix constant with k, call it kLengthPos and kIndexPos.

[Ivan Posva, 2013/05/14 18:30:30]

Done + simplified the code where we use the length and index location repeatedly
during code gen.

+  };
   intptr_t array_type_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckArrayBoundInstr);
 };
 
 
 #undef DECLARE_INSTRUCTION
 
 class Environment : public ZoneAllocated {
  public:
@@ skipping 210 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_