[interpreter] Inline Star on dispatch for some bytecodes

test/unittests/interpreter/interpreter-assembler-unittest.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 "test/unittests/interpreter/interpreter-assembler-unittest.h"
 
 #include "src/code-factory.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/node.h"
 #include "src/interface-descriptors.h"
@@ skipping 314 matching lines @@
         IsParameter(InterpreterDispatchDescriptor::kBytecodeArrayParameter),
         next_bytecode_offset_matcher);
     if (kPointerSize == 8) {
       target_bytecode_matcher = IsChangeUint32ToUint64(target_bytecode_matcher);
     }
     Matcher<Node*> code_target_matcher = m.IsLoad(
         MachineType::Pointer(),
         IsParameter(InterpreterDispatchDescriptor::kDispatchTableParameter),
         IsWordShl(target_bytecode_matcher, IsIntPtrConstant(kPointerSizeLog2)));
 
+    if (interpreter::Bytecodes::IsStarLookahead(bytecode, operand_scale)) {
+      Matcher<Node*> after_lookahead_offset =
+          IsIntPtrAdd(next_bytecode_offset_matcher,
+                      IsIntPtrConstant(interpreter::Bytecodes::Size(
+                          Bytecode::kStar, operand_scale)));
+      next_bytecode_offset_matcher =
+          IsPhi(MachineType::PointerRepresentation(),
+                next_bytecode_offset_matcher, after_lookahead_offset, _);
+      Matcher<Node*> after_lookahead_bytecode = m.IsLoad(
+          MachineType::Uint8(),
+          IsParameter(InterpreterDispatchDescriptor::kBytecodeArrayParameter),
+          after_lookahead_offset);
+      if (kPointerSize == 8) {
+        after_lookahead_bytecode =
+            IsChangeUint32ToUint64(after_lookahead_bytecode);
+      }
+      target_bytecode_matcher =
+          IsPhi(MachineRepresentation::kWord8, target_bytecode_matcher,
+                after_lookahead_bytecode, _);
+      code_target_matcher = m.IsLoad(
+          MachineType::Pointer(),
+          IsParameter(InterpreterDispatchDescriptor::kDispatchTableParameter),
+          IsWordShl(target_bytecode_matcher,
+                    IsIntPtrConstant(kPointerSizeLog2)));
+    }
+
     EXPECT_THAT(
         tail_call_node,
         IsTailCall(
             _, code_target_matcher,
             IsParameter(InterpreterDispatchDescriptor::kAccumulatorParameter),
             next_bytecode_offset_matcher,
             IsParameter(InterpreterDispatchDescriptor::kBytecodeArrayParameter),
             IsParameter(InterpreterDispatchDescriptor::kDispatchTableParameter),
             _, _));
   }
 }
 
 TARGET_TEST_F(InterpreterAssemblerTest, Jump) {
   // If debug code is enabled we emit extra code in Jump.
   if (FLAG_debug_code) return;
 
   int jump_offsets[] = {-9710, -77, 0, +3, +97109};
   TRACED_FOREACH(int, jump_offset, jump_offsets) {
     TRACED_FOREACH(interpreter::Bytecode, bytecode, kBytecodes) {
+      if (interpreter::Bytecodes::IsStarLookahead(bytecode,
+                                                  OperandScale::kSingle)) {
+        return;
+      }
+

[klaasb, 2016/07/20 11:22:55]

Jump was the only caller of DispatchTo, to which I added the DCHECK - which
breaks this test.
I'm not sure this test is really that useful to do for every bytecode?

[rmcilroy, 2016/07/20 11:36:25]

Agreed - could you instead make the check:
if (!interpreter::Bytecodes::IsJump(bytecode)) return;

       InterpreterAssemblerForTest m(this, bytecode);
       Node* tail_call_node = m.Jump(m.IntPtrConstant(jump_offset));
 
       Matcher<Node*> next_bytecode_offset_matcher = IsIntPtrAdd(
           IsParameter(InterpreterDispatchDescriptor::kBytecodeOffsetParameter),
           IsIntPtrConstant(jump_offset));
       Matcher<Node*> target_bytecode_matcher =
           m.IsLoad(MachineType::Uint8(), _, next_bytecode_offset_matcher);
       if (kPointerSize == 8) {
         target_bytecode_matcher =
@@ skipping 339 matching lines @@
     EXPECT_THAT(feedback_vector,
                 m.IsLoad(MachineType::AnyTagged(), load_literals_matcher,
                          IsIntPtrConstant(LiteralsArray::kFeedbackVectorOffset -
                                           kHeapObjectTag)));
   }
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8