Save/restore only live registers in the generator suspend/resume.

src/interpreter/bytecode-register-optimizer.h

 // Copyright 2016 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_BYTECODE_REGISTER_OPTIMIZER_H_
 #define V8_INTERPRETER_BYTECODE_REGISTER_OPTIMIZER_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/globals.h"
 #include "src/interpreter/bytecode-register-allocator.h"
@@ skipping 49 matching lines @@
 
   // Materialize all live registers and flush equivalence sets.
   void Flush();
 
   // Prepares for |bytecode|.
   template <Bytecode bytecode, AccumulatorUse accumulator_use>
   INLINE(void PrepareForBytecode()) {
     if (Bytecodes::IsJump(bytecode) || Bytecodes::IsSwitch(bytecode) ||
         bytecode == Bytecode::kDebugger ||
         bytecode == Bytecode::kSuspendGenerator ||
-        bytecode == Bytecode::kResumeGenerator) {
+        bytecode == Bytecode::kResumeGenerator ||

[rmcilroy, 2017/06/01 10:44:44]

Remove ResumeGenerator from here now.

[Jarin, 2017/06/01 12:48:22]

Done.

+        bytecode == Bytecode::kRestoreGeneratorRegisters) {
       // All state must be flushed before emitting
       // - a jump bytecode (as the register equivalents at the jump target
       //   aren't known)
       // - a switch bytecode (as the register equivalents at the switch targets
       //   aren't known)
       // - a call to the debugger (as it can manipulate locals and parameters),
       // - a generator suspend (as this involves saving all registers).
       // - a generator resume (as this involves restoring all registers).

[rmcilroy, 2017/06/01 10:44:44]

update comment please

[Jarin, 2017/06/01 12:48:22]

Done.

       Flush();
     }
 
     // Materialize the accumulator if it is read by the bytecode. The
     // accumulator is special and no other register can be materialized
     // in it's place.
     if (BytecodeOperands::ReadsAccumulator(accumulator_use)) {
       Materialize(accumulator_info_);
     }
 
@@ skipping 108 matching lines @@
   Zone* zone_;
 
   DISALLOW_COPY_AND_ASSIGN(BytecodeRegisterOptimizer);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_REGISTER_OPTIMIZER_H_