[interpreter] Inline Star on dispatch for some bytecodes

src/interpreter/interpreter-assembler.h

Index: src/interpreter/interpreter-assembler.h
diff --git a/src/interpreter/interpreter-assembler.h b/src/interpreter/interpreter-assembler.h
index 183d4ddaefff1e11306170eea5be41dee460e64a..9086323db3676f3ce2ce5089e2747d9cf4971795 100644
--- a/src/interpreter/interpreter-assembler.h
+++ b/src/interpreter/interpreter-assembler.h
@@ -218,14 +218,35 @@ class InterpreterAssembler : public CodeStubAssembler {
   // 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);
@@ -237,6 +258,7 @@ class InterpreterAssembler : public CodeStubAssembler {
   OperandScale operand_scale() const { return operand_scale_; }
 
   Bytecode bytecode_;
+  CodeStubAssembler::Variable bytecode_offset_;
   OperandScale operand_scale_;
   CodeStubAssembler::Variable interpreted_frame_pointer_;
   CodeStubAssembler::Variable accumulator_;