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

src/isolate.cc

 // Copyright 2012 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/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 1300 matching lines @@
         //       materialized by the deoptimizer. If there is a handler frame
         //       in between then {frame->sp()} would already be correct.
         Address return_sp = frame->fp() -
                             InterpreterFrameConstants::kFixedFrameSizeFromFp -
                             register_slots * kPointerSize;
 
         // Patch the bytecode offset in the interpreted frame to reflect the
         // position of the exception handler. The special builtin below will
         // take care of continuing to dispatch at that position. Also restore
         // the correct context for the handler from the interpreter register.
+        CHECK(js_frame->ReadInterpreterRegister(context_reg)->IsContext());

[neis, 2017/06/02 10:04:40]

Maybe remove this again, I guess it's a debugging leftover.

         Context* context =
             Context::cast(js_frame->ReadInterpreterRegister(context_reg));
         js_frame->PatchBytecodeOffset(static_cast<int>(offset));
 
         Code* code = *builtins()->InterpreterEnterBytecodeDispatch();
         return FoundHandler(context, code, 0, return_sp, frame->fp());
       }
 
       case StackFrame::JAVA_SCRIPT:
       case StackFrame::BUILTIN:
@@ skipping 2453 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8