[interpreter] Inline Star on dispatch for some bytecodes

src/interpreter/bytecodes.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/bytecodes.h"
 
 #include <iomanip>
 
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
@@ skipping 551 matching lines @@
   case OperandType::k##Name: \
     break;
     NON_REGISTER_OPERAND_TYPE_LIST(CASE)
     REGISTER_INPUT_OPERAND_TYPE_LIST(CASE)
 #undef CASE
   }
   return false;
 }
 
 // static
+bool Bytecodes::IsStarLookahead(Bytecode bytecode, OperandScale operand_scale) {
+  if (operand_scale == OperandScale::kSingle) {
+    switch (bytecode) {
+      case Bytecode::kLdaZero:
+      case Bytecode::kLdaSmi:
+      case Bytecode::kLdaNull:
+      case Bytecode::kLdaTheHole:
+      case Bytecode::kLdaConstant:
+      case Bytecode::kAdd:
+      case Bytecode::kSub:
+      case Bytecode::kMul:
+      case Bytecode::kAddSmi:
+      case Bytecode::kSubSmi:
+      case Bytecode::kInc:
+      case Bytecode::kDec:
+      case Bytecode::kTypeOf:
+      case Bytecode::kCall:
+      case Bytecode::kNew:
+      case Bytecode::kToNumber:
+      case Bytecode::kCreateRegExpLiteral:
+      case Bytecode::kCreateArrayLiteral:
+      case Bytecode::kCreateObjectLiteral:
+      case Bytecode::kCreateMappedArguments:
+      case Bytecode::kCreateUnmappedArguments:
+      case Bytecode::kForInPrepare:

[klaasb, 2016/07/18 19:45:46]

This one doesn't write the accumulator, but in all things I ran, it dispatched
to Star in 100% of the cases.

All of the new ones I added were found by looking at dispatch report with
https://codereview.chromium.org/2159683003/ for facebook, verge, speedometer (on
53.0.2785.8) and Octane-noopt locally. They all dispatch always or nearly always
to Star on all of them.

[rmcilroy, 2016/07/19 10:03:55]

As discussed offline, let's remove the ones which are 100% of the time  (at
least 100% with REO disabled) and instead change the bytecodes to accept an
output register, which would save on the dispatch and reduce code size.

+      case Bytecode::kForInStep:
+      case Bytecode::kResumeGenerator:
+        return true;
+      default:
+        return false;
+    }
+  }
+  return false;
+}
+
+// static
 int Bytecodes::GetNumberOfRegistersRepresentedBy(OperandType operand_type) {
   switch (operand_type) {
     case OperandType::kMaybeReg:
     case OperandType::kReg:
     case OperandType::kRegOut:
       return 1;
     case OperandType::kRegPair:
     case OperandType::kRegOutPair:
       return 2;
     case OperandType::kRegOutTriple:
@@ skipping 363 matching lines @@
   if (!FLAG_always_opt && !FLAG_prepare_always_opt &&
       pretenure == NOT_TENURED && is_function_scope) {
     result |= FastNewClosureBit::encode(true);
   }
   return result;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8