Convert diamond shaped control flow into a single conditional instruction.

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 481 matching lines @@
   M(UnboxInteger)                                                              \
   M(BoxInteger)                                                                \
   M(BinaryMintOp)                                                              \
   M(ShiftMintOp)                                                               \
   M(UnaryMintOp)                                                               \
   M(CheckArrayBound)                                                           \
   M(Constraint)                                                                \
   M(StringFromCharCode)                                                        \
   M(InvokeMathCFunction)                                                       \
   M(GuardField)                                                                \
-
+  M(IfThenElse)                                                                \
 
 #define FORWARD_DECLARATION(type) class type##Instr;
 FOR_EACH_INSTRUCTION(FORWARD_DECLARATION)
 #undef FORWARD_DECLARATION
 
 
 // Functions required in all concrete instruction classes.
 #define DECLARE_INSTRUCTION(type)                                              \
   virtual Tag tag() const { return k##type; }                                  \
   virtual void Accept(FlowGraphVisitor* visitor);                              \
@@ skipping 481 matching lines @@
 
   virtual BlockEntryInstr* GetBlock() const {
     return const_cast<BlockEntryInstr*>(this);
   }
 
   // Helper to mutate the graph during inlining. This block should be
   // replaced with new_block as a predecessor of all of this block's
   // successors.
   void ReplaceAsPredecessorWith(BlockEntryInstr* new_block);
 
+  void set_block_id(intptr_t block_id) { block_id_ = block_id; }
+
  protected:
   BlockEntryInstr(intptr_t block_id, intptr_t try_index)
       : block_id_(block_id),
         try_index_(try_index),
         preorder_number_(-1),
         postorder_number_(-1),
         dominator_(NULL),
         dominated_blocks_(1),
         last_instruction_(NULL),
         parallel_move_(NULL),
         loop_info_(NULL) { }
 
  private:
   virtual void RawSetInputAt(intptr_t i, Value* value) { UNREACHABLE(); }
 
   virtual void ClearPredecessors() = 0;
   virtual void AddPredecessor(BlockEntryInstr* predecessor) = 0;
 
-  const intptr_t block_id_;
+  intptr_t block_id_;
   const intptr_t try_index_;
   intptr_t preorder_number_;
   intptr_t postorder_number_;
   // Starting and ending lifetime positions for this block.  Used by
   // the linear scan register allocator.
   intptr_t start_pos_;
   intptr_t end_pos_;
   BlockEntryInstr* dominator_;  // Immediate dominator, NULL for graph entry.
   // TODO(fschneider): Optimize the case of one child to save space.
   GrowableArray<BlockEntryInstr*> dominated_blocks_;
@@ skipping 1637 matching lines @@
 
  private:
   const ICData* ic_data_;
   const intptr_t token_pos_;
   intptr_t operands_class_id_;  // class id of both operands.
 
   DISALLOW_COPY_AND_ASSIGN(RelationalOpInstr);
 };
 
 
+// TODO(vegorov): ComparisonInstr should be switched to use IfTheElseInstr for
+// materialization of true and false constants.
+class IfThenElseInstr : public TemplateDefinition<2> {
+ public:
+  IfThenElseInstr(Token::Kind kind,
+                  Value* left,
+                  Value* right,
+                  Value* if_true,
+                  Value* if_false)
+      : kind_(kind),
+        if_true_(Smi::Cast(if_true->BoundConstant()).Value()),
+        if_false_(Smi::Cast(if_false->BoundConstant()).Value()) {
+    ASSERT(Token::IsEqualityOperator(kind));
+    SetInputAt(0, left);
+    SetInputAt(1, right);
+  }
+
+  // Returns true if this instruction is supported on the current platform.
+  static bool IsSupported();
+
+  // Returns true if this combination of comparison and values flowing on
+  // the true and false paths is supported on the current platform.
+  static bool Supports(ComparisonInstr* comparison, Value* v1, Value* v2);
+
+  DECLARE_INSTRUCTION(IfThenElse)
+
+  virtual void PrintOperandsTo(BufferFormatter* f) const;
+
+  virtual CompileType ComputeType() const;
+
+  virtual void InferRange();
+
+  virtual bool CanDeoptimize() const { return false; }
+  virtual bool HasSideEffect() const { return false; }
+
+  virtual bool AttributesEqual(Instruction* other) const {
+    return kind_ == other->AsIfThenElse()->kind_;
+  }
+
+  virtual bool AffectedBySideEffect() const {
+    return false;
+  }
+
+  Value* left() const { return inputs_[0]; }
+  Value* right() const { return inputs_[1]; }
+  intptr_t if_true() const { return if_true_; }
+  intptr_t if_false() const { return if_false_; }
+
+  Token::Kind kind() const { return kind_; }
+
+ private:
+  const Token::Kind kind_;
+  const intptr_t if_true_;
+  const intptr_t if_false_;
+
+  DISALLOW_COPY_AND_ASSIGN(IfThenElseInstr);
+};
+
+
 class StaticCallInstr : public TemplateDefinition<0> {
  public:
   StaticCallInstr(intptr_t token_pos,
                   const Function& function,
                   const Array& argument_names,
                   ZoneGrowableArray<PushArgumentInstr*>* arguments)
       : token_pos_(token_pos),
         function_(function),
         argument_names_(argument_names),
         arguments_(arguments),
@@ skipping 2007 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_