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

runtime/vm/simulator_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 <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_DBC)
 
@@ skipping 1068 matching lines @@
       fp_ = reinterpret_cast<RawObject**>(fp_[0]);                             \
       thread->set_top_exit_frame_info(reinterpret_cast<uword>(fp_));           \
       thread->set_top_resource(top_resource);                                  \
       thread->set_vm_tag(vm_tag);                                              \
       return special_[kExceptionSpecialIndex];                                 \
     }                                                                          \
     pp = SimulatorHelpers::FrameCode(FP)->ptr()->object_pool_->ptr();          \
     goto DispatchAfterException;                                               \
   } while (0)
 
-// Runtime call helpers: handle invocation and potential exception after return.
+// Runtime call helpers: handle invocation and potential exception
+// after return.  The caller may have changed the return address on
+// the stack.  Handle this by updating the pc.
 #define INVOKE_RUNTIME(Func, Args)                                             \
   if (!InvokeRuntime(thread, this, Func, Args)) {                              \
     HANDLE_EXCEPTION;                                                          \
+  } else {                                                                     \
+    pc = reinterpret_cast<uint32_t*>(fp_[kSavedCallerPcSlotFromFp]);           \
   }
 
 #define INVOKE_NATIVE(Func, Args)                                              \
   if (!InvokeNative(thread, this, Func, &Args)) {                              \
     HANDLE_EXCEPTION;                                                          \
+  } else {                                                                     \
+    pc = reinterpret_cast<uint32_t*>(fp_[kSavedCallerPcSlotFromFp]);           \
   }
 
 #define INVOKE_NATIVE_WRAPPER(Func, Args)                                      \
   if (!InvokeNativeWrapper(thread, this, Func, &Args)) {                       \
     HANDLE_EXCEPTION;                                                          \
+  } else {                                                                     \
+    pc = reinterpret_cast<uint32_t*>(fp_[kSavedCallerPcSlotFromFp]);           \
   }
 
 #define LOAD_CONSTANT(index) (pp->data()[(index)].raw_obj_)
 
 
 // Returns true if deoptimization succeeds.
 DART_FORCE_INLINE bool Simulator::Deoptimize(Thread* thread,
                                              RawObjectPool** pp,
                                              uint32_t** pc,
                                              RawObject*** FP,
                                              RawObject*** SP,
                                              bool is_lazy) {
   // Note: frame translation will take care of preserving result at the
   // top of the stack. See CompilerDeoptInfo::CreateDeoptInfo.
 
   // Make sure we preserve SP[0] when entering synthetic frame below.
   (*SP)++;
 
   // Leaf runtime function DeoptimizeCopyFrame expects a Dart frame.
   // The code in this frame may not cause GC.
   // DeoptimizeCopyFrame and DeoptimizeFillFrame are leaf runtime calls.
   EnterSyntheticFrame(FP, SP, *pc - (is_lazy ? 1 : 0));
   const intptr_t frame_size_in_bytes =
       DLRT_DeoptimizeCopyFrame(reinterpret_cast<uword>(*FP), is_lazy ? 1 : 0);
+  // Copy frame updates the caller pc (which is our pc).
+  *pc = reinterpret_cast<uint32_t*>((*FP)[kSavedCallerPcSlotFromFp]);
   LeaveSyntheticFrame(FP, SP);
 
   *SP = *FP + (frame_size_in_bytes / kWordSize);
   EnterSyntheticFrame(FP, SP, *pc - (is_lazy ? 1 : 0));
   DLRT_DeoptimizeFillFrame(reinterpret_cast<uword>(*FP));
 
   // We are now inside a valid frame.
   {
     *++(*SP) = 0;  // Space for the result: number of materialization args.
     Exit(thread, *FP, *SP + 1, /*pc=*/0);
@@ skipping 408 matching lines @@
 #if !defined(PRODUCT)
     {
       const uint32_t original_bc =
           static_cast<uint32_t>(reinterpret_cast<uintptr_t>(
               thread->isolate()->debugger()->GetPatchedStubAddress(
                   reinterpret_cast<uword>(pc))));
 
       SP[1] = null_value;
       Exit(thread, FP, SP + 2, pc);
       NativeArguments args(thread, 0, NULL, SP + 1);
-      INVOKE_RUNTIME(DRT_BreakpointRuntimeHandler, args)
+      INVOKE_RUNTIME(DRT_BreakpointRuntimeHandler, args);
       DISPATCH_OP(original_bc);
     }
 #else
     // There should be no debug breaks in product mode.
     UNREACHABLE();
 #endif
     DISPATCH();
   }
 
   {
@@ skipping 1083 matching lines @@
     // Check if it is a fake PC marking the entry frame.
     if ((reinterpret_cast<uword>(pc) & 2) != 0) {
       const intptr_t argc = reinterpret_cast<uword>(pc) >> 2;
       fp_ = reinterpret_cast<RawObject**>(FrameArguments(FP, argc + 1)[0]);
       thread->set_top_exit_frame_info(reinterpret_cast<uword>(fp_));
       thread->set_top_resource(top_resource);
       thread->set_vm_tag(vm_tag);
       return result;
     }
 
+    // If we have a pending lazy deopt then the caller's pc is stored
+    // in the isolate.
+    uint32_t* caller_pc = pc;
+    if ((reinterpret_cast<uword>(pc) ==
+         StubCode::DeoptimizeLazyFromReturn_entry()->EntryPoint())) {
+      caller_pc =
+          reinterpret_cast<uint32_t*>(thread->isolate()->FindPendingDeopt(
+              reinterpret_cast<uword>(SavedCallerFP(FP))));
+    }
+
     // Look at the caller to determine how many arguments to pop.
-    const uint8_t argc = Bytecode::DecodeArgc(pc[-1]);
+    const uint8_t argc = Bytecode::DecodeArgc(caller_pc[-1]);
 
     // Restore SP, FP and PP. Push result and dispatch.
     SP = FrameArguments(FP, argc);
     FP = SavedCallerFP(FP);
     pp = SimulatorHelpers::FrameCode(FP)->ptr()->object_pool_->ptr();
     *SP = result;
     DISPATCH();
   }
 
   {
@@ skipping 1094 matching lines @@
     pc_ = pc;
   }
 
   buf->Longjmp();
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC