[interpreter] Inline Star on dispatch for some bytecodes

src/interpreter/interpreter-assembler.cc

 // 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.
 
 #include "src/interpreter/interpreter-assembler.h"
 
 #include <limits>
 #include <ostream>
 
 #include "src/code-factory.h"
@@ skipping 12 matching lines @@
 using compiler::Node;
 
 InterpreterAssembler::InterpreterAssembler(Isolate* isolate, Zone* zone,
                                            Bytecode bytecode,
                                            OperandScale operand_scale)
     : CodeStubAssembler(isolate, zone, InterpreterDispatchDescriptor(isolate),
                         Code::ComputeFlags(Code::BYTECODE_HANDLER),
                         Bytecodes::ToString(bytecode),
                         Bytecodes::ReturnCount(bytecode)),
       bytecode_(bytecode),
+      bytecode_offset_(this, MachineType::PointerRepresentation()),
       operand_scale_(operand_scale),
       interpreted_frame_pointer_(this, MachineType::PointerRepresentation()),
       accumulator_(this, MachineRepresentation::kTagged),
       accumulator_use_(AccumulatorUse::kNone),
       made_call_(false),
       disable_stack_check_across_call_(false),
       stack_pointer_before_call_(nullptr) {
   accumulator_.Bind(
       Parameter(InterpreterDispatchDescriptor::kAccumulatorParameter));
+  bytecode_offset_.Bind(
+      Parameter(InterpreterDispatchDescriptor::kBytecodeOffsetParameter));
   if (FLAG_trace_ignition) {
     TraceBytecode(Runtime::kInterpreterTraceBytecodeEntry);
   }
 }
 
 InterpreterAssembler::~InterpreterAssembler() {
   // If the following check fails the handler does not use the
   // accumulator in the way described in the bytecode definitions in
   // bytecodes.h.
   DCHECK_EQ(accumulator_use_, Bytecodes::GetAccumulatorUse(bytecode_));
@@ skipping 24 matching lines @@
 
 Node* InterpreterAssembler::GetContext() {
   return LoadRegister(Register::current_context());
 }
 
 void InterpreterAssembler::SetContext(Node* value) {
   StoreRegister(value, Register::current_context());
 }
 
 Node* InterpreterAssembler::BytecodeOffset() {
-  return Parameter(InterpreterDispatchDescriptor::kBytecodeOffsetParameter);
+  return bytecode_offset_.value();
 }
 
 Node* InterpreterAssembler::BytecodeArrayTaggedPointer() {
   if (made_call_) {
     // If we have made a call, restore bytecode array from stack frame in case
     // the debugger has swapped us to the patched debugger bytecode array.
     return LoadRegister(Register::bytecode_array());
   } else {
     return Parameter(InterpreterDispatchDescriptor::kBytecodeArrayParameter);
   }
@@ skipping 402 matching lines @@
     Goto(&ok);
   }
 
   // Update budget.
   Bind(&ok);
   StoreNoWriteBarrier(MachineRepresentation::kWord32,
                       BytecodeArrayTaggedPointer(), budget_offset,
                       new_budget.value());
 }
 
+Node* InterpreterAssembler::Advance() {
+  return Advance(Bytecodes::Size(bytecode_, operand_scale_));
+}
+
 Node* InterpreterAssembler::Advance(int delta) {
-  return IntPtrAdd(BytecodeOffset(), IntPtrConstant(delta));
+  return Advance(IntPtrConstant(delta));
 }
 
 Node* InterpreterAssembler::Advance(Node* delta) {
-  return IntPtrAdd(BytecodeOffset(), delta);
+  if (FLAG_trace_ignition) {
+    TraceBytecode(Runtime::kInterpreterTraceBytecodeExit);
+  }
+  Node* next_offset = IntPtrAdd(BytecodeOffset(), delta);
+  bytecode_offset_.Bind(next_offset);
+  return next_offset;
 }
 
 Node* InterpreterAssembler::Jump(Node* delta) {
   UpdateInterruptBudget(delta);
-  return DispatchTo(Advance(delta));
+  Node* previous_offset = BytecodeOffset();
+  Node* dispatch = DispatchTo(Advance(delta));
+  bytecode_offset_.Bind(previous_offset);

[rmcilroy, 2016/07/19 20:18:27]

I don't think we need this line do we? We are be exiting this basic block, so I
don't think the updates we've done to bytecode_offset_ will apply in any future
Dispatch in a different basic block.

[klaasb, 2016/07/20 09:26:24]

Done.

+  return dispatch;
 }
 
 void InterpreterAssembler::JumpConditional(Node* condition, Node* delta) {
   Label match(this), no_match(this);
 
   BranchIf(condition, &match, &no_match);
   Bind(&match);
   Jump(delta);
   Bind(&no_match);
   Dispatch();
 }
 
 void InterpreterAssembler::JumpIfWordEqual(Node* lhs, Node* rhs, Node* delta) {
   JumpConditional(WordEqual(lhs, rhs), delta);
 }
 
 void InterpreterAssembler::JumpIfWordNotEqual(Node* lhs, Node* rhs,
                                               Node* delta) {
   JumpConditional(WordNotEqual(lhs, rhs), delta);
 }
 
+Node* InterpreterAssembler::LoadBytecode(compiler::Node* bytecode_offset) {
+  Node* bytecode =
+      Load(MachineType::Uint8(), BytecodeArrayTaggedPointer(), bytecode_offset);
+  if (kPointerSize == 8) {
+    bytecode = ChangeUint32ToUint64(bytecode);
+  }
+  return bytecode;
+}
+
+void InterpreterAssembler::StarDispatchLookahead(Variable& target_bytecode) {

[rmcilroy, 2016/07/19 20:18:27]

no non-const references -
https://google.github.io/styleguide/cppguide.html#Reference_Arguments

Make this a pointer instead, or (possibly better), just pass in the
target_bytecode as a node, and return a node with the (possibly updated)
bytecode, and keep all the Variable logic contained in this function.

[klaasb, 2016/07/20 09:26:24]

Done.

+  Label do_inline_star(this), done(this);
+
+  Node* star_bytecode = IntPtrConstant(static_cast<int>(Bytecode::kStar));
+  Node* is_star = WordEqual(target_bytecode.value(), star_bytecode);
+  BranchIf(is_star, &do_inline_star, &done);
+  Bind(&do_inline_star);

[rmcilroy, 2016/07/19 20:18:27]

nit - newline above.

[klaasb, 2016/07/20 09:26:24]

Done.

+  {
+    InlineStar();
+    target_bytecode.Bind(LoadBytecode(BytecodeOffset()));
+    Goto(&done);
+  }
+  Bind(&done);
+}
+
+void InterpreterAssembler::InlineStar() {
+  Bytecode previous_bytecode = bytecode_;
+  AccumulatorUse previous_acc_use = accumulator_use_;
+
+  bytecode_ = Bytecode::kStar;
+  accumulator_use_ = AccumulatorUse::kNone;
+
+  if (FLAG_trace_ignition) {
+    TraceBytecode(Runtime::kInterpreterTraceBytecodeEntry);
+  }
+  StoreRegister(GetAccumulator(), BytecodeOperandReg(0));
+
+  DCHECK_EQ(accumulator_use_, Bytecodes::GetAccumulatorUse(bytecode_));
+
+  Advance();
+  bytecode_ = previous_bytecode;
+  accumulator_use_ = previous_acc_use;
+}
+
 Node* InterpreterAssembler::Dispatch() {
-  return DispatchTo(Advance(Bytecodes::Size(bytecode_, operand_scale_)));
+  Node* previous_offset = BytecodeOffset();
+  Node* target_offset = Advance();
+  Node* target_bytecode = LoadBytecode(target_offset);
+  Variable var_bytecode(this, MachineRepresentation::kWord8);
+  var_bytecode.Bind(target_bytecode);
+
+  if (Bytecodes::IsStarLookahead(bytecode_, operand_scale_)) {
+    StarDispatchLookahead(var_bytecode);
+  }
+  Node* dispatch = DispatchToBytecode(var_bytecode.value(), BytecodeOffset());
+  bytecode_offset_.Bind(previous_offset);

[rmcilroy, 2016/07/19 20:18:27]

same comment as above.

[klaasb, 2016/07/20 09:26:24]

Done.

+  return dispatch;
 }
 
 Node* InterpreterAssembler::DispatchTo(Node* new_bytecode_offset) {
-  Node* target_bytecode = Load(
-      MachineType::Uint8(), BytecodeArrayTaggedPointer(), new_bytecode_offset);
-  if (kPointerSize == 8) {
-    target_bytecode = ChangeUint32ToUint64(target_bytecode);
-  }
+  Node* target_bytecode = LoadBytecode(new_bytecode_offset);

[rmcilroy, 2016/07/19 20:18:27]

nit - DCHECK here that !Bytecodes::IsStarLookahead(bytecode_, operand_scale_).

[klaasb, 2016/07/20 09:26:24]

Done.

+  return DispatchToBytecode(target_bytecode, new_bytecode_offset);
+}
 
+Node* InterpreterAssembler::DispatchToBytecode(Node* target_bytecode,
+                                               Node* new_bytecode_offset) {
   if (FLAG_trace_ignition_dispatches) {
     TraceBytecodeDispatch(target_bytecode);
   }
 
   Node* target_code_entry =
       Load(MachineType::Pointer(), DispatchTableRawPointer(),
            WordShl(target_bytecode, IntPtrConstant(kPointerSizeLog2)));
 
   return DispatchToBytecodeHandlerEntry(target_code_entry, new_bytecode_offset);
 }
 
 Node* InterpreterAssembler::DispatchToBytecodeHandler(Node* handler,
                                                       Node* bytecode_offset) {
   Node* handler_entry =
       IntPtrAdd(handler, IntPtrConstant(Code::kHeaderSize - kHeapObjectTag));
   return DispatchToBytecodeHandlerEntry(handler_entry, bytecode_offset);
 }
 
 Node* InterpreterAssembler::DispatchToBytecodeHandlerEntry(
     Node* handler_entry, Node* bytecode_offset) {
-  if (FLAG_trace_ignition) {
-    TraceBytecode(Runtime::kInterpreterTraceBytecodeExit);
-  }
-
   InterpreterDispatchDescriptor descriptor(isolate());
   Node* args[] = {GetAccumulatorUnchecked(), bytecode_offset,
                   BytecodeArrayTaggedPointer(), DispatchTableRawPointer()};
   return TailCallBytecodeDispatch(descriptor, handler_entry, args);
 }
 
 void InterpreterAssembler::DispatchWide(OperandScale operand_scale) {
   // Dispatching a wide bytecode requires treating the prefix
   // bytecode a base pointer into the dispatch table and dispatching
   // the bytecode that follows relative to this base.
   //
   //   Indices 0-255 correspond to bytecodes with operand_scale == 0
   //   Indices 256-511 correspond to bytecodes with operand_scale == 1
   //   Indices 512-767 correspond to bytecodes with operand_scale == 2
   Node* next_bytecode_offset = Advance(1);
-  Node* next_bytecode = Load(MachineType::Uint8(), BytecodeArrayTaggedPointer(),
-                             next_bytecode_offset);
+  Node* next_bytecode = LoadBytecode(next_bytecode_offset);
   if (kPointerSize == 8) {
     next_bytecode = ChangeUint32ToUint64(next_bytecode);
   }

[rmcilroy, 2016/07/19 20:18:27]

Remove extra ChangeUint32ToUint64 given it is already done in LoadBytecode

[klaasb, 2016/07/20 09:26:24]

Done.

 
   if (FLAG_trace_ignition_dispatches) {
     TraceBytecodeDispatch(next_bytecode);
   }
 
   Node* base_index;
   switch (operand_scale) {
     case OperandScale::kDouble:
       base_index = IntPtrConstant(1 << kBitsPerByte);
       break;
@@ skipping 173 matching lines @@
     Goto(&loop);
   }
   Bind(&done_loop);
 
   return array;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8