[interpreter] Inline Star on dispatch for some bytecodes

src/interpreter/interpreter-assembler.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERPRETER_INTERPRETER_ASSEMBLER_H_
 #define V8_INTERPRETER_INTERPRETER_ASSEMBLER_H_
 
 #include "src/allocation.h"
 #include "src/base/smart-pointers.h"
 #include "src/builtins.h"
@@ skipping 200 matching lines @@
   compiler::Node* BytecodeSignedOperand(int operand_index,
                                         OperandSize operand_size);
   compiler::Node* BytecodeUnsignedOperand(int operand_index,
                                           OperandSize operand_size);
 
   // Jump relative to the current bytecode by |jump_offset| if the
   // |condition| is true. Helper function for JumpIfWordEqual and
   // JumpIfWordNotEqual.
   void JumpConditional(compiler::Node* condition, compiler::Node* jump_offset);
 
+  // Returns BytecodeOffset() advanced by the current bytecode's size.
+  // Note: this does not update BytecodeOffset() itself.

[rmcilroy, 2016/07/19 10:03:56]

Now that you have a variable for bytecode_offset, could you have these update
BytecodeOffset() too? That might mean you don't need to pass around
target_offset as a variable to StarDispatchLookahead / InlineStar.

[klaasb, 2016/07/19 14:24:13]

Done. Need to re-bind the offset to the previous one at the end of every
Dispatch since code generated after a first Dispatch expects to operate on the
previous bytecode's offset, e.g. for operands or further dispatches.

+  compiler::Node* Advance();
+
   // Returns BytecodeOffset() advanced by delta bytecodes. Note: this does not
   // update BytecodeOffset() itself.
   compiler::Node* Advance(int delta);
   compiler::Node* Advance(compiler::Node* delta);
 
+  // Load the bytecode at |bytecode_offset|.
+  compiler::Node* LoadBytecode(compiler::Node* bytecode_offset);
+
   // Starts next instruction dispatch at |new_bytecode_offset|.
   compiler::Node* DispatchTo(compiler::Node* new_bytecode_offset);
 
+  // Look ahead for Star and inline it, will bind the next bytecode to dispatch
+  // to, to |target_bytecode| and its offset to |target_offset|.
+  void StarDispatchLookahead(Variable& target_bytecode,
+                             Variable& target_offset);
+
+  // Build code for Star at |target_offset| and bind |target_offset| to the
+  // next offset after Star
+  void InlineStar(Variable& target_offset);

[rmcilroy, 2016/07/19 10:03:56]

nit - could you move these above DispatchTo (group the DispatchX methods
together.

[klaasb, 2016/07/19 14:24:13]

Done.

+
+  // Dispatch to |target_bytecode| at |new_bytecode_offset|.
+  // |target_bytecode| should be equivalent to loading from the offset.
+  compiler::Node* DispatchToBytecode(compiler::Node* target_bytecode,
+                                     compiler::Node* new_bytecode_offset);
+
   // Dispatch to the bytecode handler with code offset |handler|.
   compiler::Node* DispatchToBytecodeHandler(compiler::Node* handler,
                                             compiler::Node* bytecode_offset);
 
   // Dispatch to the bytecode handler with code entry point |handler_entry|.
   compiler::Node* DispatchToBytecodeHandlerEntry(
       compiler::Node* handler_entry, compiler::Node* bytecode_offset);
 
   OperandScale operand_scale() const { return operand_scale_; }
 
   Bytecode bytecode_;
+  CodeStubAssembler::Variable bytecode_offset_;
   OperandScale operand_scale_;
   CodeStubAssembler::Variable interpreted_frame_pointer_;
   CodeStubAssembler::Variable accumulator_;
   AccumulatorUse accumulator_use_;
   bool made_call_;
 
   bool disable_stack_check_across_call_;
   compiler::Node* stack_pointer_before_call_;
 
   DISALLOW_COPY_AND_ASSIGN(InterpreterAssembler);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_INTERPRETER_ASSEMBLER_H_