Do not rely on code patching on DBC for lazy deoptimization.

runtime/vm/stub_code_dbc.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_DBC)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 31 matching lines @@
 
 
 // Not executed, but used as a sentinel in Simulator::JumpToFrame.
 void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
   __ Trap();
 }
 
 
 void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
   __ DeoptRewind();
+  __ Trap();
 }
 
 
 // TODO(vegorov) Don't generate this stub.
 void StubCode::GenerateFixCallersTargetStub(Assembler* assembler) {
   __ Trap();
 }
 
 
 // TODO(vegorov) Don't generate these stubs.
 void StubCode::GenerateAllocationStubForClass(Assembler* assembler,
                                               const Class& cls) {
   __ Trap();
 }
 
 
 // TODO(vegorov) Don't generate this stub.
 void StubCode::GenerateMegamorphicMissStub(Assembler* assembler) {
   __ Trap();
 }
 
 
 // These deoptimization stubs are only used to populate stack frames
 // with something meaningful to make sure GC can scan the stack during
 // the last phase of deoptimization which materializes objects.
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
-  __ Trap();
+  __ Deopt(0 /* unused */, 0 /* lazy */);
+  __ Trap();  // Not reached: pc is updated as part of deoptimization.
 }
 
 
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
-  __ Trap();
+  __ Deopt(0 /* unused */, 0 /* lazy */);
+  __ Trap();  // Not reached: pc is updated as part of deoptimization.
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   __ Trap();
 }
 
 
 void StubCode::GenerateFrameAwaitingMaterializationStub(Assembler* assembler) {
   __ Trap();
 }
 
 
 void StubCode::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
   __ Trap();
 }
 
 
 // Print the stop message.
 DEFINE_LEAF_RUNTIME_ENTRY(void, PrintStopMessage, 1, const char* message) {
   OS::Print("Stop message: %s\n", message);
 }
 END_LEAF_RUNTIME_ENTRY
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC