Merge experimental/a64 to bleeding_edge.

src/deoptimizer.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2670 matching lines @@
                                    JSFunction* function)
     : frame_size_(frame_size),
       function_(function),
       top_(kZapUint32),
       pc_(kZapUint32),
       fp_(kZapUint32),
       context_(kZapUint32),
       constant_pool_(kZapUint32) {
   // Zap all the registers.
   for (int r = 0; r < Register::kNumRegisters; r++) {
+    // TODO(jbramley): It isn't safe to use kZapUint32 here. If the register
+    // isn't used before the next safepoint, the GC will try to scan it as a
+    // tagged value. kZapUint32 looks like a valid tagged pointer, but it isn't.
     SetRegister(r, kZapUint32);
   }
 
   // Zap all the slots.
   for (unsigned o = 0; o < frame_size; o += kPointerSize) {
     SetFrameSlot(o, kZapUint32);
   }
 }
 
 
@@ skipping 756 matching lines @@
 
 void DeoptimizedFrameInfo::Iterate(ObjectVisitor* v) {
   v->VisitPointer(BitCast<Object**>(&function_));
   v->VisitPointers(parameters_, parameters_ + parameters_count_);
   v->VisitPointers(expression_stack_, expression_stack_ + expression_count_);
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal