Implement rewind on all platforms except for dbc.

BUG=

Review URL: https://codereview.chromium.org/2534413005 .

runtime/observatory/lib/src/elements/debugger.dart

@@ -209,7 +209,8 @@ class DownCommand extends DebuggerCommand {
       debugger.downFrame(count);
       debugger.console.print('frame = ${debugger.currentFrame}');
     } catch (e) {
-      debugger.console.print('frame must be in range [${e.start},${e.end-1}]');
+      debugger.console.print(
+          'frame must be in range [${e.start}..${e.end-1}]');
     }
     return new Future.value(null);
   }
@@ -243,7 +244,8 @@ class UpCommand extends DebuggerCommand {
       debugger.upFrame(count);
       debugger.console.print('frame = ${debugger.currentFrame}');
     } on RangeError catch (e) {
-      debugger.console.print('frame must be in range [${e.start},${e.end-1}]');
+      debugger.console.print(
+          'frame must be in range [${e.start}..${e.end-1}]');
     }
     return new Future.value(null);
   }
@@ -279,7 +281,8 @@ class FrameCommand extends DebuggerCommand {
       debugger.currentFrame = frame;
       debugger.console.print('frame = ${debugger.currentFrame}');
     } on RangeError catch (e) {
-      debugger.console.print('frame must be in range [${e.start},${e.end-1}]');
+      debugger.console.print(
+          'frame must be in range [${e.start}..${e.end-1}]');
     }
     return new Future.value(null);
   }
@@ -403,6 +406,73 @@ class StepCommand extends DebuggerCommand {
       'Syntax: step\n';
 }
 
+class RewindCommand extends DebuggerCommand {
+  RewindCommand(Debugger debugger) : super(debugger, 'rewind', []);
+
+  Future run(List<String> args) async {
+    try {
+      int count = 1;
+      if (args.length == 1) {
+        count = int.parse(args[0]);
+      } else if (args.length > 1) {
+        debugger.console.print('rewind expects 0 or 1 argument');
+        return;
+      } else if (count < 1 || count > debugger.stackDepth) {
+        debugger.console.print(
+            'frame must be in range [1..${debugger.stackDepth - 1}]');
+        return;
+      }
+      await debugger.rewind(count);
+    } on S.ServerRpcException catch(e) {
+      if (e.code == S.ServerRpcException.kCannotResume) {
+        debugger.console.printRed(e.data['details']);
+      } else {
+        rethrow;
+      }
+    }
+  }
+
+  String helpShort = 'Rewind the stack to a previous frame';
+
+  String helpLong =
+      'Rewind the stack to a previous frame.\n'
+      '\n'
+      'Syntax: rewind\n'
+      '        rewind <count>\n';
+}
+
+class ReloadCommand extends DebuggerCommand {
+  ReloadCommand(Debugger debugger) : super(debugger, 'reload', []);
+
+  Future run(List<String> args) async {
+    try {
+      int count = 1;
+      if (args.length > 0) {
+        debugger.console.print('reload expects no arguments');
+        return;
+      }
+      await debugger.isolate.reloadSources();
+      debugger.console.print('reload complete');
+      await debugger.refreshStack();
+    } on S.ServerRpcException catch(e) {
+      if (e.code == S.ServerRpcException.kIsolateReloadBarred ||
+          e.code == S.ServerRpcException.kIsolateReloadFailed ||
+          e.code == S.ServerRpcException.kIsolateIsReloading) {
+        debugger.console.printRed(e.data['details']);
+      } else {
+        rethrow;
+      }
+    }
+  }
+
+  String helpShort = 'Reload the sources for the current isolate';
+
+  String helpLong =
+      'Reload the sources for the current isolate.\n'
+      '\n'
+      'Syntax: reload\n';
+}
+
 class ClsCommand extends DebuggerCommand {
   ClsCommand(Debugger debugger) : super(debugger, 'cls', []) {}
 
@@ -663,8 +733,8 @@ class BreakCommand extends DebuggerCommand {
         var script = loc.script;
         await script.load();
         if (loc.line < 1 || loc.line > script.lines.length) {
-          debugger.console
+          debugger.console.print(
-              .print('line number must be in range [1,${script.lines.length}]');
+              'line number must be in range [1..${script.lines.length}]');
           return;
         }
         try {
@@ -744,7 +814,7 @@ class ClearCommand extends DebuggerCommand {
     var script = loc.script;
     if (loc.line < 1 || loc.line > script.lines.length) {
       debugger.console
-          .print('line number must be in range [1,${script.lines.length}]');
+          .print('line number must be in range [1..${script.lines.length}]');
       return;
     }
     var lineInfo = script.getLine(loc.line);
@@ -899,7 +969,6 @@ class IsolateCommand extends DebuggerCommand {
       : super(debugger, 'isolate', [
           new IsolateListCommand(debugger),
           new IsolateNameCommand(debugger),
-          new IsolateReloadCommand(debugger),
         ]) {
     alias = 'i';
   }
@@ -1042,27 +1111,6 @@ class IsolateNameCommand extends DebuggerCommand {
       'Syntax: isolate name <name>\n';
 }
 
-class IsolateReloadCommand extends DebuggerCommand {
-  IsolateReloadCommand(Debugger debugger) : super(debugger, 'reload', []);
-
-  Future run(List<String> args) async {
-    if (debugger.isolate == null) {
-      debugger.console.print('There is no current vm');
-      return;
-    }
-
-    await debugger.isolate.reloadSources();
-
-    debugger.console.print('Isolate reloading....');
-  }
-
-  String helpShort = 'Reload the sources for the current isolate.';
-
-  String helpLong = 'Reload the sources for the current isolate.\n'
-      '\n'
-      'Syntax: reload\n';
-}
-
 class InfoCommand extends DebuggerCommand {
   InfoCommand(Debugger debugger)
       : super(debugger, 'info', [
@@ -1371,7 +1419,9 @@ class ObservatoryDebugger extends Debugger {
       new LogCommand(this),
       new PauseCommand(this),
       new PrintCommand(this),
+      new ReloadCommand(this),
       new RefreshCommand(this),
+      new RewindCommand(this),
       new SetCommand(this),
       new SmartNextCommand(this),
       new StepCommand(this),
@@ -1879,6 +1929,20 @@ class ObservatoryDebugger extends Debugger {
       return new Future.value(null);
     }
   }
+
+  Future rewind(int count) {
+    if (isolatePaused()) {
+      var event = isolate.pauseEvent;
+      if (event is M.PauseExitEvent) {
+        console.print("Type 'continue' [F7] to exit the isolate");
+        return new Future.value(null);
+      }
+      return isolate.rewind(count);
+    } else {
+      console.print('The program must be paused');
+      return new Future.value(null);
+    }
+  }
 }
 
 class DebuggerPageElement extends HtmlElement implements Renderable {
@@ -2513,7 +2577,9 @@ class DebuggerFrameElement extends HtmlElement implements Renderable {
   }
 
   bool matchFrame(S.Frame newFrame) {
-    return newFrame.function.id == _frame.function.id;
+    return (newFrame.function.id == _frame.function.id &&
+            newFrame.location.script.id ==
+            frame.location.script.id);
   }
 
   void updateFrame(S.Frame newFrame) {

runtime/observatory/lib/src/service/object.dart

@@ -42,11 +42,13 @@ class ServerRpcException extends RpcException implements M.RequestException {
   static const kStreamNotSubscribed = 104;
   static const kIsolateMustBeRunnable = 105;
   static const kIsolateMustBePaused = 106;
+  static const kCannotResume = 107;
   static const kIsolateIsReloading = 1000;
   static const kFileSystemAlreadyExists = 1001;
   static const kFileSystemDoesNotExist = 1002;
   static const kFileDoesNotExist = 1003;
   static const kIsolateReloadFailed = 1004;
+  static const kIsolateReloadBarred = 1005;
 
   int code;
   Map data;
@@ -1279,7 +1281,6 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
   bool loading = true;
   bool runnable = false;
   bool ioEnabled = false;
-  bool reloading = false;
   M.IsolateStatus get status {
     if (paused) {
       return M.IsolateStatus.paused;
@@ -1344,13 +1345,12 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
       params['pause'] = pause;
     }
     return invokeRpc('reloadSources', params).then((result) {
-      reloading = true;
+      _cache.clear();
       return result;
     });
   }
 
   void _handleIsolateReloadEvent(ServiceEvent event) {
-    reloading = false;
     if (event.reloadError != null) {
       // Failure.
       print('Reload failed: ${event.reloadError}');
@@ -1777,6 +1777,10 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
     return invokeRpc('resume', {'step': 'Out'});
   }
 
+  Future rewind(int count) {
+    return invokeRpc('resume', {'step': 'Rewind', 'frameIndex': count});
+  }
+
   Future setName(String newName) {
     return invokeRpc('setName', {'name': newName});
   }

runtime/observatory/tests/service/pause_idle_isolate_test.dart

@@ -52,5 +52,6 @@ hasStoppedAtBreakpoint,
 
 main(args) => runIsolateTests(args, tests,
                               testeeConcurrent: testMain,
-                              trace_service: true,
+                              verbose_vm: true,
-                              verbose_vm: true);
+                              extraArgs: [ '--trace-service',
+                                           '--trace-service-verbose' ]);

runtime/observatory/tests/service/pause_on_start_and_exit_test.dart

@@ -86,5 +86,6 @@ main(args) => runIsolateTests(args, tests,
                               testeeConcurrent: testMain,
                               pause_on_start: true,
                               pause_on_exit: true,
-                              trace_service: true,
+                              verbose_vm: true,
-                              verbose_vm: true);
+                              extraArgs: [ '--trace-service',
+                                           '--trace-service-verbose' ]);

runtime/observatory/tests/service/pause_on_start_then_step_test.dart

@@ -89,5 +89,6 @@ main(args) => runIsolateTests(args, tests,
                               testeeConcurrent: testMain,
                               pause_on_start: true,
                               pause_on_exit: true,
-                              trace_service: true,
+                              verbose_vm: true,
-                              verbose_vm: true);
+                              extraArgs: [ '--trace-service',
+                                           '--trace-service-verbose' ]);

runtime/observatory/tests/service/rewind_optimized_out_test.dart

@@ -0,0 +1,86 @@
+// 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.
+// VMOptions=--error_on_bad_type --error_on_bad_override
+
+import 'dart:developer';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+
+const alwaysInline = "AlwaysInline";
+const noInline = "NeverInline";
+
+int LINE_A = 35;
+int LINE_B = 40;
+int LINE_C = 43;
+int LINE_D = 47;
+
+int global = 0;
+
+@noInline
+b3(x) {
+  int sum = 0;
+  try {
+    for (int i = 0; i < x; i++) {
+      sum += x;
+    }
+  } catch (e) {
+    print("caught $e");
+  }
+  if (global >= 100) {
+    debugger();
+  }
+  global = global + 1;  // Line A
+  return sum;
+}
+
+@alwaysInline
+b2(x) => b3(x);  // Line B
+
+@alwaysInline
+b1(x) => b2(x);  // Line C
+
+test() {
+  while (true) {
+    b1(10000);  // Line D
+  }
+}
+
+var tests = [
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // We are at our breakpoint with global=100.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Rewind the top stack frame.
+    bool caughtException;
+    try {
+      result = await isolate.rewind(1);
+      expect(false, isTrue, reason:'Unreachable');
+    } on ServerRpcException catch(e) {
+      caughtException = true;
+      expect(e.code, equals(ServerRpcException.kCannotResume));
+      expect(e.message,
+             'Cannot rewind to frame 1 due to conflicting compiler '
+             'optimizations. Run the vm with --no-prune-dead-locals to '
+             'disallow these optimizations. Next valid rewind frame is 4.');
+    }
+    expect(caughtException, isTrue);
+  },
+];
+
+
+main(args) => runIsolateTests(args, tests, testeeConcurrent: test,
+                              extraArgs:
+                              ['--trace-rewind',
+                               '--prune-dead-locals',
+                               '--enable-inlining-annotations',
+                               '--no-background-compilation',
+                               '--optimization-counter-threshold=10']);

runtime/observatory/tests/service/rewind_test.dart

@@ -0,0 +1,173 @@
+// 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.
+// VMOptions=--error_on_bad_type --error_on_bad_override
+
+import 'dart:developer';
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+
+const alwaysInline = "AlwaysInline";
+const noInline = "NeverInline";
+
+int LINE_A = 35;
+int LINE_B = 40;
+int LINE_C = 43;
+int LINE_D = 47;
+
+int global = 0;
+
+@noInline
+b3(x) {
+  int sum = 0;
+  try {
+    for (int i = 0; i < x; i++) {
+      sum += x;
+    }
+  } catch (e) {
+    print("caught $e");
+  }
+  if (global >= 100) {
+    debugger();
+  }
+  global = global + 1;  // Line A
+  return sum;
+}
+
+@alwaysInline
+b2(x) => b3(x);  // Line B
+
+@alwaysInline
+b1(x) => b2(x);  // Line C
+
+test() {
+  while (true) {
+    b1(10000);  // Line D
+  }
+}
+
+var tests = [
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // We are not able to rewind frame 0.
+    bool caughtException;
+    try {
+      await isolate.rewind(0);
+      expect(false, isTrue, reason:'Unreachable');
+    } on ServerRpcException catch(e) {
+      caughtException = true;
+      expect(e.code, equals(ServerRpcException.kCannotResume));
+      expect(e.message, 'Frame must be in bounds [1..9]: saw 0');
+    }
+    expect(caughtException, isTrue);
+  },
+
+  (Isolate isolate) async {
+    // We are not able to rewind frame 10.
+    bool caughtException;
+    try {
+      await isolate.rewind(10);
+      expect(false, isTrue, reason:'Unreachable');
+    } on ServerRpcException catch(e) {
+      caughtException = true;
+      expect(e.code, equals(ServerRpcException.kCannotResume));
+      expect(e.message, 'Frame must be in bounds [1..9]: saw 10');
+    }
+    expect(caughtException, isTrue);
+  },
+
+  (Isolate isolate) async {
+    // We are at our breakpoint with global=100.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Rewind the top stack frame.
+    result = await isolate.rewind(1);
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_B),
+
+  (Isolate isolate) async {
+    var result = await isolate.resume();
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // global still is equal to 100.  We did not execute "global++".
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Resume again, for fun.
+    result = await isolate.resume();
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // global is now 101.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('101'));
+
+    // Rewind up to 'test'/
+    result = await isolate.rewind(3);
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_D),
+
+  (Isolate isolate) async {
+    // Reset global to 0 and start again.
+    var result = await isolate.rootLibrary.evaluate('global=0');
+    print('set global to $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('0'));
+
+    result = await isolate.resume();
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_A),
+
+  (Isolate isolate) async {
+    // We are at our breakpoint with global=100.
+    var result = await isolate.rootLibrary.evaluate('global');
+    print('global is $result');
+    expect(result.type, equals('Instance'));
+    expect(result.valueAsString, equals('100'));
+
+    // Rewind the top 2 stack frames.
+    result = await isolate.rewind(2);
+    expect(result['type'], equals('Success'));
+  },
+
+  hasStoppedAtBreakpoint,
+  stoppedAtLine(LINE_C),
+];
+
+
+main(args) => runIsolateTests(args, tests, testeeConcurrent: test,
+                              extraArgs:
+                              ['--trace-rewind',
+                               '--no-prune-dead-locals',
+                               '--enable-inlining-annotations',
+                               '--no-background-compilation',
+                               '--optimization-counter-threshold=10']);

runtime/observatory/tests/service/service.status

@@ -64,6 +64,8 @@ evaluate_activation_in_method_class_test: CompileTimeError # Issue 24478
 get_allocation_samples_test: RuntimeError # Profiling unimplemented.
 get_cpu_profile_timeline_rpc_test: RuntimeError # Profiling unimplemented.
 implicit_getter_setter_test: RuntimeError # Field guards unimplemented.
+rewind_test: RuntimeError # Issue 27878
+rewind_optimized_out_test: RuntimeError # Issue 27878
 
 [ $hot_reload || $hot_reload_rollback ]
 # Skip all service tests because random reloads interfere.

runtime/observatory/tests/service/service_test_common.dart

@@ -234,6 +234,10 @@ IsolateTest stoppedAtLine(int line) {
   return (Isolate isolate) async {
     print("Checking we are at line $line");
 
+    // Make sure that the isolate has stopped.
+    isolate.reload();
+    expect(isolate.pauseEvent is! M.ResumeEvent, isTrue);
+
     ServiceMap stack = await isolate.getStack();
     expect(stack.type, equals('Stack'));
 

runtime/observatory/tests/service/set_vm_name_rpc_test.dart

@@ -32,4 +32,6 @@ var tests = [
   },
 ];
 
-main(args) async => runVMTests(args, tests, trace_service: true);
+main(args) async => runVMTests(args, tests,
+                               extraArgs: [ '--trace-service',
+                                            '--trace-service-verbose' ]);

runtime/observatory/tests/service/step_over_await_test.dart

@@ -1,7 +1,7 @@
 // Copyright (c) 2015, 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.
-// VMOptions=--error_on_bad_type --error_on_bad_override  --verbose_debug --trace_service
+// VMOptions=--error_on_bad_type --error_on_bad_override  --verbose_debug
 
 import 'dart:async';
 import 'dart:developer';

runtime/observatory/tests/service/test_helper.dart

@@ -90,15 +90,12 @@ class _ServiceTesteeLauncher {
   Future<Process> _spawnProcess(bool pause_on_start,
                                 bool pause_on_exit,
                                 bool pause_on_unhandled_exceptions,
-                                bool trace_service,
-                                bool trace_compiler,
                                 bool testeeControlsServer,
-                                bool useAuthToken) {
+                                bool useAuthToken,
+                                List<String> extraArgs) {
     assert(pause_on_start != null);
     assert(pause_on_exit != null);
     assert(pause_on_unhandled_exceptions != null);
-    assert(trace_service != null);
-    assert(trace_compiler != null);
     assert(testeeControlsServer != null);
     assert(useAuthToken != null);
 
@@ -106,39 +103,29 @@ class _ServiceTesteeLauncher {
       return _spawnSkyProcess(pause_on_start,
                               pause_on_exit,
                               pause_on_unhandled_exceptions,
-                              trace_service,
+                              testeeControlsServer,
-                              trace_compiler,
+                              extraArgs);
-                              testeeControlsServer);
     } else {
       return _spawnDartProcess(pause_on_start,
                                pause_on_exit,
                                pause_on_unhandled_exceptions,
-                               trace_service,
-                               trace_compiler,
                                testeeControlsServer,
-                               useAuthToken);
+                               useAuthToken,
+                               extraArgs);
     }
   }
 
   Future<Process> _spawnDartProcess(bool pause_on_start,
                                     bool pause_on_exit,
                                     bool pause_on_unhandled_exceptions,
-                                    bool trace_service,
-                                    bool trace_compiler,
                                     bool testeeControlsServer,
-                                    bool useAuthToken) {
+                                    bool useAuthToken,
+                                    List<String> extraArgs) {
     assert(!_shouldLaunchSkyShell());
 
     String dartExecutable = Platform.executable;
 
     var fullArgs = [];
-    if (trace_service) {
-      fullArgs.add('--trace-service');
-      fullArgs.add('--trace-service-verbose');
-    }
-    if (trace_compiler) {
-      fullArgs.add('--trace-compiler');
-    }
     if (pause_on_start) {
       fullArgs.add('--pause-isolates-on-start');
     }
@@ -148,6 +135,9 @@ class _ServiceTesteeLauncher {
     if (pause_on_unhandled_exceptions) {
       fullArgs.add('--pause-isolates-on-unhandled-exceptions');
     }
+    if (extraArgs != null) {
+      fullArgs.addAll(extraArgs);
+    }
 
     fullArgs.addAll(Platform.executableArguments);
     if (!testeeControlsServer) {
@@ -166,22 +156,14 @@ class _ServiceTesteeLauncher {
   Future<Process> _spawnSkyProcess(bool pause_on_start,
                                    bool pause_on_exit,
                                    bool pause_on_unhandled_exceptions,
-                                   bool trace_service,
+                                   bool testeeControlsServer,
-                                   bool trace_compiler,
+                                   List<String> extraArgs) {
-                                   bool testeeControlsServer) {
     assert(_shouldLaunchSkyShell());
 
     String dartExecutable = _skyShellPath();
 
     var dartFlags = [];
     var fullArgs = [];
-    if (trace_service) {
-      dartFlags.add('--trace_service');
-      dartFlags.add('--trace_service_verbose');
-    }
-    if (trace_compiler) {
-      dartFlags.add('--trace_compiler');
-    }
     if (pause_on_start) {
       dartFlags.add('--pause_isolates_on_start');
       fullArgs.add('--start-paused');
@@ -194,6 +176,9 @@ class _ServiceTesteeLauncher {
     }
     // Override mirrors.
     dartFlags.add('--enable_mirrors=true');
+    if (extraArgs != null) {
+      fullArgs.addAll(extraArgs);
+    }
 
     fullArgs.addAll(Platform.executableArguments);
     if (!testeeControlsServer) {
@@ -223,17 +208,15 @@ class _ServiceTesteeLauncher {
   Future<Uri> launch(bool pause_on_start,
                      bool pause_on_exit,
                      bool pause_on_unhandled_exceptions,
-                     bool trace_service,
-                     bool trace_compiler,
                      bool testeeControlsServer,
-                     bool useAuthToken) {
+                     bool useAuthToken,
+                     List<String> extraArgs) {
     return _spawnProcess(pause_on_start,
                   pause_on_exit,
                   pause_on_unhandled_exceptions,
-                  trace_service,
-                  trace_compiler,
                   testeeControlsServer,
-                  useAuthToken).then((p) {
+                  useAuthToken,
+                  extraArgs).then((p) {
       Completer<Uri> completer = new Completer<Uri>();
       process = p;
       Uri uri;
@@ -288,12 +271,11 @@ void setupAddresses(Uri serverAddress) {
 
 class _ServiceTesterRunner {
   void run({List<String> mainArgs,
+            List<String> extraArgs,
             List<VMTest> vmTests,
             List<IsolateTest> isolateTests,
             bool pause_on_start: false,
             bool pause_on_exit: false,
-            bool trace_service: false,
-            bool trace_compiler: false,
             bool verbose_vm: false,
             bool pause_on_unhandled_exceptions: false,
             bool testeeControlsServer: false,
@@ -301,9 +283,8 @@ class _ServiceTesterRunner {
     var process = new _ServiceTesteeLauncher();
     process.launch(pause_on_start, pause_on_exit,
                    pause_on_unhandled_exceptions,
-                   trace_service, trace_compiler,
                    testeeControlsServer,
-                   useAuthToken).then((Uri serverAddress) async {
+                   useAuthToken, extraArgs).then((Uri serverAddress) async {
       if (mainArgs.contains("--gdb")) {
         var pid = process.process.pid;
         var wait = new Duration(seconds: 10);
@@ -364,12 +345,11 @@ Future runIsolateTests(List<String> mainArgs,
                         testeeConcurrent(),
                         bool pause_on_start: false,
                         bool pause_on_exit: false,
-                        bool trace_service: false,
-                        bool trace_compiler: false,
                         bool verbose_vm: false,
                         bool pause_on_unhandled_exceptions: false,
                         bool testeeControlsServer: false,
-                        bool useAuthToken: false}) async {
+                        bool useAuthToken: false,
+                        List<String> extraArgs}) async {
   assert(!pause_on_start || testeeBefore == null);
   if (_isTestee()) {
     new _ServiceTesteeRunner().run(testeeBefore: testeeBefore,
@@ -379,11 +359,10 @@ Future runIsolateTests(List<String> mainArgs,
   } else {
     new _ServiceTesterRunner().run(
         mainArgs: mainArgs,
+        extraArgs: extraArgs,
         isolateTests: tests,
         pause_on_start: pause_on_start,
         pause_on_exit: pause_on_exit,
-        trace_service: trace_service,
-        trace_compiler: trace_compiler,
         verbose_vm: verbose_vm,
         pause_on_unhandled_exceptions: pause_on_unhandled_exceptions,
         testeeControlsServer: testeeControlsServer,
@@ -406,10 +385,9 @@ void runIsolateTestsSynchronous(List<String> mainArgs,
                                  void testeeConcurrent(),
                                  bool pause_on_start: false,
                                  bool pause_on_exit: false,
-                                 bool trace_service: false,
-                                 bool trace_compiler: false,
                                  bool verbose_vm: false,
-                                 bool pause_on_unhandled_exceptions: false}) {
+                                 bool pause_on_unhandled_exceptions: false,
+                                 List<String> extraArgs}) {
   assert(!pause_on_start || testeeBefore == null);
   if (_isTestee()) {
     new _ServiceTesteeRunner().runSync(testeeBeforeSync: testeeBefore,
@@ -419,11 +397,10 @@ void runIsolateTestsSynchronous(List<String> mainArgs,
   } else {
     new _ServiceTesterRunner().run(
         mainArgs: mainArgs,
+        extraArgs: extraArgs,
         isolateTests: tests,
         pause_on_start: pause_on_start,
         pause_on_exit: pause_on_exit,
-        trace_service: trace_service,
-        trace_compiler: trace_compiler,
         verbose_vm: verbose_vm,
         pause_on_unhandled_exceptions: pause_on_unhandled_exceptions);
   }
@@ -440,10 +417,9 @@ Future runVMTests(List<String> mainArgs,
                    testeeConcurrent(),
                    bool pause_on_start: false,
                    bool pause_on_exit: false,
-                   bool trace_service: false,
-                   bool trace_compiler: false,
                    bool verbose_vm: false,
-                   bool pause_on_unhandled_exceptions: false}) async {
+                   bool pause_on_unhandled_exceptions: false,
+                   List<String> extraArgs}) async {
   if (_isTestee()) {
     new _ServiceTesteeRunner().run(testeeBefore: testeeBefore,
                                    testeeConcurrent: testeeConcurrent,
@@ -452,11 +428,10 @@ Future runVMTests(List<String> mainArgs,
   } else {
     new _ServiceTesterRunner().run(
         mainArgs: mainArgs,
+        extraArgs: extraArgs,
         vmTests: tests,
         pause_on_start: pause_on_start,
         pause_on_exit: pause_on_exit,
-        trace_service: trace_service,
-        trace_compiler: trace_compiler,
         verbose_vm: verbose_vm,
         pause_on_unhandled_exceptions: pause_on_unhandled_exceptions);
   }

runtime/vm/code_generator.cc

@@ -2215,6 +2215,15 @@ DEFINE_RUNTIME_ENTRY(DeoptimizeMaterialize, 0) {
 }
 
 
+DEFINE_RUNTIME_ENTRY(RewindPostDeopt, 0) {
+#if !defined(DART_PRECOMPILED_RUNTIME)
+#if !defined(PRODUCT)
+  isolate->debugger()->RewindPostDeopt();
+#endif  // !PRODUCT
+#endif  // !DART_PRECOMPILED_RUNTIME
+  UNREACHABLE();
+}
+
 DEFINE_LEAF_RUNTIME_ENTRY(intptr_t,
                           BigintCompare,
                           2,

runtime/vm/dart_entry.cc

@@ -551,7 +551,7 @@ RawObject* DartLibraryCalls::HandleMessage(const Object& handler,
     // If the isolate is being debugged and the debugger was stepping
     // through code, enable single stepping so debugger will stop
     // at the first location the user is interested in.
-    isolate->debugger()->SetSingleStep();
+    isolate->debugger()->SetResumeAction(Debugger::kStepInto);
   }
   const Object& result =
       Object::Handle(zone, DartEntry::InvokeFunction(function, args));

runtime/vm/debugger.cc

@@ -6,6 +6,8 @@
 
 #include "include/dart_api.h"
 
+#include "platform/address_sanitizer.h"
+
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ -42,6 +44,7 @@ DEFINE_FLAG(bool,
             trace_debugger_stacktrace,
             false,
             "Trace debugger stacktrace collection");
+DEFINE_FLAG(bool, trace_rewind, false, "Trace frame rewind");
 DEFINE_FLAG(bool, verbose_debug, false, "Verbose debugger messages");
 DEFINE_FLAG(bool,
             steal_breakpoints,
@@ -850,6 +853,24 @@ RawObject* ActivationFrame::GetStackVar(intptr_t slot_index) {
 }
 
 
+bool ActivationFrame::IsRewindable() const {
+  if (deopt_frame_.IsNull()) {
+    return true;
+  }
+  // TODO(turnidge): This is conservative.  It looks at all values in
+  // the deopt_frame_ even though some of them may correspond to other
+  // inlined frames.
+  Object& obj = Object::Handle();
+  for (int i = 0; i < deopt_frame_.Length(); i++) {
+    obj = deopt_frame_.At(i);
+    if (obj.raw() == Symbols::OptimizedOut().raw()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+
 void ActivationFrame::PrintContextMismatchError(intptr_t ctx_slot,
                                                 intptr_t frame_ctx_level,
                                                 intptr_t var_ctx_level) {
@@ -1108,9 +1129,13 @@ void ActivationFrame::PrintToJSONObject(JSONObject* jsobj, bool full) {
   }
 }
 
+static bool IsFunctionVisible(const Function& function) {
+  return FLAG_show_invisible_frames || function.is_visible();
+}
+
 
 void DebuggerStackTrace::AddActivation(ActivationFrame* frame) {
-  if (FLAG_show_invisible_frames || frame->function().is_visible()) {
+  if (IsFunctionVisible(frame->function())) {
     trace_.Add(frame);
   }
 }
@@ -1237,6 +1262,8 @@ Debugger::Debugger()
       breakpoint_locations_(NULL),
       code_breakpoints_(NULL),
       resume_action_(kContinue),
+      resume_frame_index_(-1),
+      post_deopt_frame_index_(-1),
       ignore_breakpoints_(false),
       pause_event_(NULL),
       obj_cache_(NULL),
@@ -1300,10 +1327,13 @@ static RawFunction* ResolveLibraryFunction(const Library& library,
 }
 
 
-bool Debugger::SetupStepOverAsyncSuspension() {
+bool Debugger::SetupStepOverAsyncSuspension(const char** error) {
   ActivationFrame* top_frame = TopDartFrame();
   if (!IsAtAsyncJump(top_frame)) {
     // Not at an async operation.
+    if (error) {
+      *error = "Isolate must be paused at an async suspension point";
+    }
     return false;
   }
   Object& closure = Object::Handle(top_frame->GetAsyncOperation());
@@ -1313,24 +1343,42 @@ bool Debugger::SetupStepOverAsyncSuspension() {
   Breakpoint* bpt = SetBreakpointAtActivation(Instance::Cast(closure), true);
   if (bpt == NULL) {
     // Unable to set the breakpoint.
+    if (error) {
+      *error = "Unable to set breakpoint at async suspension point";
+    }
     return false;
   }
   return true;
 }
 
 
-void Debugger::SetSingleStep() {
+bool Debugger::SetResumeAction(ResumeAction action,
-  resume_action_ = kSingleStep;
+                               intptr_t frame_index,
-}
+                               const char** error) {
-
+  if (error) {
-
+    *error = NULL;
-void Debugger::SetStepOver() {
+  }
-  resume_action_ = kStepOver;
+  resume_frame_index_ = -1;
-}
+  switch (action) {
-
+    case kStepInto:
-
+    case kStepOver:
-void Debugger::SetStepOut() {
+    case kStepOut:
-  resume_action_ = kStepOut;
+    case kContinue:
+      resume_action_ = action;
+      return true;
+    case kStepRewind:
+      if (!CanRewindFrame(frame_index, error)) {
+        return false;
+      }
+      resume_action_ = kStepRewind;
+      resume_frame_index_ = frame_index;
+      return true;
+    case kStepOverAsyncSuspension:
+      return SetupStepOverAsyncSuspension(error);
+    default:
+      UNREACHABLE();
+      return false;
+  }
 }
 
 
@@ -1622,6 +1670,7 @@ void Debugger::PauseException(const Instance& exc) {
   ASSERT(stack_trace_ == NULL);
   stack_trace_ = stack_trace;
   Pause(&event);
+  HandleSteppingRequest(stack_trace_);  // we may get a rewind request
   stack_trace_ = NULL;
 }
 
@@ -2547,7 +2596,7 @@ void Debugger::EnterSingleStepMode() {
 void Debugger::HandleSteppingRequest(DebuggerStackTrace* stack_trace,
                                      bool skip_next_step) {
   stepping_fp_ = 0;
-  if (resume_action_ == kSingleStep) {
+  if (resume_action_ == kStepInto) {
     // When single stepping, we need to deoptimize because we might be
     // stepping into optimized code.  This happens in particular if
     // the isolate has been interrupted, but can happen in other cases
@@ -2557,7 +2606,7 @@ void Debugger::HandleSteppingRequest(DebuggerStackTrace* stack_trace,
     isolate_->set_single_step(true);
     skip_next_step_ = skip_next_step;
     if (FLAG_verbose_debug) {
-      OS::Print("HandleSteppingRequest- kSingleStep\n");
+      OS::Print("HandleSteppingRequest- kStepInto\n");
     }
   } else if (resume_action_ == kStepOver) {
     DeoptimizeWorld();
@@ -2582,6 +2631,244 @@ void Debugger::HandleSteppingRequest(DebuggerStackTrace* stack_trace,
     if (FLAG_verbose_debug) {
       OS::Print("HandleSteppingRequest- kStepOut %" Px "\n", stepping_fp_);
     }
+  } else if (resume_action_ == kStepRewind) {
+    if (FLAG_trace_rewind) {
+      OS::PrintErr("Rewinding to frame %" Pd "\n", resume_frame_index_);
+      OS::PrintErr(
+          "-------------------------\n"
+          "All frames...\n\n");
+      StackFrameIterator iterator(false);
+      StackFrame* frame = iterator.NextFrame();
+      intptr_t num = 0;
+      while ((frame != NULL)) {
+        OS::PrintErr("#%04" Pd " %s\n", num++, frame->ToCString());
+        frame = iterator.NextFrame();
+      }
+    }
+    RewindToFrame(resume_frame_index_);
+    UNREACHABLE();
+  }
+}
+
+
+static intptr_t FindNextRewindFrameIndex(DebuggerStackTrace* stack,
+                                         intptr_t frame_index) {
+  for (intptr_t i = frame_index + 1; i < stack->Length(); i++) {
+    ActivationFrame* frame = stack->FrameAt(i);
+    if (frame->IsRewindable()) {
+      return i;
+    }
+  }
+  return -1;
+}
+
+
+// Can the top frame be rewound?
+bool Debugger::CanRewindFrame(intptr_t frame_index, const char** error) const {
+  // check rewind pc is found
+  DebuggerStackTrace* stack = Isolate::Current()->debugger()->StackTrace();
+  intptr_t num_frames = stack->Length();
+  if (frame_index < 1 || frame_index >= num_frames) {
+    if (error) {
+      *error = Thread::Current()->zone()->PrintToString(
+          "Frame must be in bounds [1..%" Pd
+          "]: "
+          "saw %" Pd "",
+          num_frames - 1, frame_index);
+    }
+    return false;
+  }
+  ActivationFrame* frame = stack->FrameAt(frame_index);
+  if (!frame->IsRewindable()) {
+    intptr_t next_index = FindNextRewindFrameIndex(stack, frame_index);
+    if (next_index > 0) {
+      *error = Thread::Current()->zone()->PrintToString(
+          "Cannot rewind to frame %" Pd
+          " due to conflicting compiler "
+          "optimizations. "
+          "Run the vm with --no-prune-dead-locals to disallow these "
+          "optimizations. "
+          "Next valid rewind frame is %" Pd ".",
+          frame_index, next_index);
+    } else {
+      *error = Thread::Current()->zone()->PrintToString(
+          "Cannot rewind to frame %" Pd
+          " due to conflicting compiler "
+          "optimizations. "
+          "Run the vm with --no-prune-dead-locals to disallow these "
+          "optimizations.",
+          frame_index);
+    }
+    return false;
+  }
+  return true;
+}
+
+
+// Given a return address pc, find the "rewind" pc, which is the pc
+// before the corresponding call.
+static uword LookupRewindPc(const Code& code, uword pc) {
+  ASSERT(!code.is_optimized());
+  ASSERT(code.ContainsInstructionAt(pc));
+
+  uword pc_offset = pc - code.PayloadStart();
+  const PcDescriptors& descriptors =
+      PcDescriptors::Handle(code.pc_descriptors());
+  PcDescriptors::Iterator iter(
+      descriptors, RawPcDescriptors::kRewind | RawPcDescriptors::kIcCall |
+                       RawPcDescriptors::kUnoptStaticCall);
+  intptr_t rewind_deopt_id = -1;
+  uword rewind_pc = 0;
+  while (iter.MoveNext()) {
+    if (iter.Kind() == RawPcDescriptors::kRewind) {
+      // Remember the last rewind so we don't need to iterator twice.
+      rewind_pc = code.PayloadStart() + iter.PcOffset();
+      rewind_deopt_id = iter.DeoptId();
+    }
+    if ((pc_offset == iter.PcOffset()) && (iter.DeoptId() == rewind_deopt_id)) {
+      return rewind_pc;
+    }
+  }
+  return 0;
+}
+
+
+void Debugger::RewindToFrame(intptr_t frame_index) {
+  Thread* thread = Thread::Current();
+  Zone* zone = thread->zone();
+  Code& code = Code::Handle(zone);
+  Function& function = Function::Handle(zone);
+
+  // Find the requested frame.
+  StackFrameIterator iterator(false);
+  intptr_t current_frame = 0;
+  for (StackFrame* frame = iterator.NextFrame(); frame != NULL;
+       frame = iterator.NextFrame()) {
+    ASSERT(frame->IsValid());
+    if (frame->IsDartFrame()) {
+      code = frame->LookupDartCode();
+      function = code.function();
+      if (!IsFunctionVisible(function)) {
+        continue;
+      }
+      if (code.is_optimized()) {
+        intptr_t sub_index = 0;
+        for (InlinedFunctionsIterator it(code, frame->pc()); !it.Done();
+             it.Advance()) {
+          if (current_frame == frame_index) {
+            RewindToOptimizedFrame(frame, code, sub_index);
+            UNREACHABLE();
+          }
+          current_frame++;
+          sub_index++;
+        }
+      } else {
+        if (current_frame == frame_index) {
+          // We are rewinding to an unoptimized frame.
+          RewindToUnoptimizedFrame(frame, code);
+          UNREACHABLE();
+        }
+        current_frame++;
+      }
+    }
+  }
+  UNIMPLEMENTED();
+}
+
+
+void Debugger::RewindToUnoptimizedFrame(StackFrame* frame, const Code& code) {
+  // We will be jumping out of the debugger rather than exiting this
+  // function, so prepare the debugger state.
+  stack_trace_ = NULL;
+  resume_action_ = kContinue;
+  resume_frame_index_ = -1;
+  EnterSingleStepMode();
+
+  uword rewind_pc = LookupRewindPc(code, frame->pc());
+  if (FLAG_trace_rewind && rewind_pc == 0) {
+    OS::PrintErr("Unable to find rewind pc for pc(%" Px ")\n", frame->pc());
+  }
+  ASSERT(rewind_pc != 0);
+  if (FLAG_trace_rewind) {
+    OS::PrintErr(
+        "===============================\n"
+        "Rewinding to unoptimized frame:\n"
+        "    rewind_pc(0x%" Px ") sp(0x%" Px ") fp(0x%" Px
+        ")\n"
+        "===============================\n",
+        rewind_pc, frame->sp(), frame->fp());
+  }
+  Exceptions::JumpToFrame(Thread::Current(), rewind_pc, frame->sp(),
+                          frame->fp(), true /* clear lazy deopt at target */);
+  UNREACHABLE();
+}
+
+
+void Debugger::RewindToOptimizedFrame(StackFrame* frame,
+                                      const Code& optimized_code,
+                                      intptr_t sub_index) {
+  post_deopt_frame_index_ = sub_index;
+
+  // We will be jumping out of the debugger rather than exiting this
+  // function, so prepare the debugger state.
+  stack_trace_ = NULL;
+  resume_action_ = kContinue;
+  resume_frame_index_ = -1;
+  EnterSingleStepMode();
+
+  if (FLAG_trace_rewind) {
+    OS::PrintErr(
+        "===============================\n"
+        "Deoptimizing frame for rewind:\n"
+        "    deopt_pc(0x%" Px ") sp(0x%" Px ") fp(0x%" Px
+        ")\n"
+        "===============================\n",
+        frame->pc(), frame->sp(), frame->fp());
+  }
+  Thread* thread = Thread::Current();
+  thread->set_resume_pc(frame->pc());
+  uword deopt_stub_pc = StubCode::DeoptForRewind_entry()->EntryPoint();
+  Exceptions::JumpToFrame(thread, deopt_stub_pc, frame->sp(), frame->fp(),
+                          true /* clear lazy deopt at target */);
+  UNREACHABLE();
+}
+
+
+void Debugger::RewindPostDeopt() {
+  intptr_t rewind_frame = post_deopt_frame_index_;
+  post_deopt_frame_index_ = -1;
+  if (FLAG_trace_rewind) {
+    OS::PrintErr("Post deopt, jumping to frame %" Pd "\n", rewind_frame);
+    OS::PrintErr(
+        "-------------------------\n"
+        "All frames...\n\n");
+    StackFrameIterator iterator(false);
+    StackFrame* frame = iterator.NextFrame();
+    intptr_t num = 0;
+    while ((frame != NULL)) {
+      OS::PrintErr("#%04" Pd " %s\n", num++, frame->ToCString());
+      frame = iterator.NextFrame();
+    }
+  }
+
+  Thread* thread = Thread::Current();
+  Zone* zone = thread->zone();
+  Code& code = Code::Handle(zone);
+
+  StackFrameIterator iterator(false);
+  intptr_t current_frame = 0;
+  for (StackFrame* frame = iterator.NextFrame(); frame != NULL;
+       frame = iterator.NextFrame()) {
+    ASSERT(frame->IsValid());
+    if (frame->IsDartFrame()) {
+      code = frame->LookupDartCode();
+      ASSERT(!code.is_optimized());
+      if (current_frame == rewind_frame) {
+        RewindToUnoptimizedFrame(frame, code);
+        UNREACHABLE();
+      }
+      current_frame++;
+    }
   }
 }
 
@@ -2793,7 +3080,7 @@ RawError* Debugger::PauseBreakpoint() {
 
     // We are at the entry of an async function.
     // We issue a step over to resume at the point after the await statement.
-    SetStepOver();
+    SetResumeAction(kStepOver);
     // When we single step from a user breakpoint, our next stepping
     // point will be at the exact same pc.  Skip it.
     HandleSteppingRequest(stack_trace_, true /* skip next step */);
@@ -2846,7 +3133,7 @@ void Debugger::PauseDeveloper(const String& msg) {
   // We are in the native call to Developer_debugger.  the developer
   // gets a better experience by not seeing this call. To accomplish
   // this, we continue execution until the call exits (step out).
-  SetStepOut();
+  SetResumeAction(kStepOut);
   HandleSteppingRequest(stack_trace_);
 
   stack_trace_ = NULL;

runtime/vm/debugger.h

@@ -276,6 +276,9 @@ class ActivationFrame : public ZoneAllocated {
   // to the user and can be debugged.
   bool IsDebuggable() const;
 
+  // Returns true if it is possible to rewind the debugger to this frame.
+  bool IsRewindable() const;
+
   // The context level of a frame is the context level at the
   // PC/token index of the frame. It determines the depth of the context
   // chain that belongs to the function of this activation frame.
@@ -373,6 +376,15 @@ class DebuggerStackTrace : public ZoneAllocated {
 
 class Debugger {
  public:
+  enum ResumeAction {
+    kContinue,
+    kStepInto,
+    kStepOver,
+    kStepOut,
+    kStepRewind,
+    kStepOverAsyncSuspension,
+  };
+
   typedef void EventHandler(ServiceEvent* event);
 
   Debugger();
@@ -412,11 +424,10 @@ class Debugger {
   void RemoveBreakpoint(intptr_t bp_id);
   Breakpoint* GetBreakpointById(intptr_t id);
 
-  // Will return false if we are not at an await.
+  bool SetResumeAction(ResumeAction action,
-  bool SetupStepOverAsyncSuspension();
+                       intptr_t frame_index = 1,
-  void SetStepOver();
+                       const char** error = NULL);
-  void SetSingleStep();
+
-  void SetStepOut();
   bool IsStepping() const { return resume_action_ != kContinue; }
 
   bool IsPaused() const { return pause_event_ != NULL; }
@@ -513,11 +524,15 @@ class Debugger {
 
   intptr_t limitBreakpointId() { return next_id_; }
 
- private:
+  // Callback to the debugger to continue frame rewind, post-deoptimization.
-  enum ResumeAction { kContinue, kStepOver, kStepOut, kSingleStep };
+  void RewindPostDeopt();
 
+ private:
   RawError* PauseRequest(ServiceEvent::EventKind kind);
 
+  // Will return false if we are not at an await.
+  bool SetupStepOverAsyncSuspension(const char** error);
+
   bool NeedsIsolateEvents();
   bool NeedsDebugEvents();
   void InvokeEventHandler(ServiceEvent* event);
@@ -588,6 +603,15 @@ class Debugger {
   void HandleSteppingRequest(DebuggerStackTrace* stack_trace,
                              bool skip_next_step = false);
 
+  // Can we rewind to the indicated frame?
+  bool CanRewindFrame(intptr_t frame_index, const char** error) const;
+
+  void RewindToFrame(intptr_t frame_index);
+  void RewindToUnoptimizedFrame(StackFrame* frame, const Code& code);
+  void RewindToOptimizedFrame(StackFrame* frame,
+                              const Code& code,
+                              intptr_t post_deopt_frame_index);
+
   Isolate* isolate_;
   Dart_Port isolate_id_;  // A unique ID for the isolate in the debugger.
   bool initialized_;
@@ -601,6 +625,8 @@ class Debugger {
 
   // Tells debugger what to do when resuming execution after a breakpoint.
   ResumeAction resume_action_;
+  intptr_t resume_frame_index_;
+  intptr_t post_deopt_frame_index_;
 
   // Do not call back to breakpoint handler if this flag is set.
   // Effectively this means ignoring breakpoints. Set when Dart code may

runtime/vm/debugger_api_impl.cc

@@ -485,7 +485,7 @@ DART_EXPORT Dart_Handle Dart_SetStepOver() {
   DARTSCOPE(Thread::Current());
   Isolate* I = T->isolate();
   CHECK_DEBUGGER(I);
-  I->debugger()->SetStepOver();
+  I->debugger()->SetResumeAction(Debugger::kStepOver);
   return Api::Success();
 }
 
@@ -494,7 +494,7 @@ DART_EXPORT Dart_Handle Dart_SetStepInto() {
   DARTSCOPE(Thread::Current());
   Isolate* I = T->isolate();
   CHECK_DEBUGGER(I);
-  I->debugger()->SetSingleStep();
+  I->debugger()->SetResumeAction(Debugger::kStepInto);
   return Api::Success();
 }
 
@@ -503,7 +503,7 @@ DART_EXPORT Dart_Handle Dart_SetStepOut() {
   DARTSCOPE(Thread::Current());
   Isolate* I = T->isolate();
   CHECK_DEBUGGER(I);
-  I->debugger()->SetStepOut();
+  I->debugger()->SetResumeAction(Debugger::kStepOut);
   return Api::Success();
 }
 

runtime/vm/exceptions.cc

@@ -189,7 +189,6 @@ static bool FindExceptionHandler(Thread* thread,
 static void FindErrorHandler(uword* handler_pc,
                              uword* handler_sp,
                              uword* handler_fp) {
-  // TODO(turnidge): Is there a faster way to get the next entry frame?
   StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);
@@ -228,7 +227,17 @@ static uword RemapExceptionPCForDeopt(Thread* thread,
         break;
       }
     }
+  }
+#endif  // !DBC
+  return program_counter;
+}
 
+
+static void ClearLazyDeopts(Thread* thread, uword frame_pointer) {
+#if !defined(TARGET_ARCH_DBC)
+  MallocGrowableArray<PendingLazyDeopt>* pending_deopts =
+      thread->isolate()->pending_deopts();
+  if (pending_deopts->length() > 0) {
     // We may be jumping over frames scheduled for lazy deopt. Remove these
     // frames from the pending deopt table, but only after unmarking them so
     // any stack walk that happens before the stack is unwound will still work.
@@ -264,7 +273,6 @@ static uword RemapExceptionPCForDeopt(Thread* thread,
 #endif
   }
 #endif  // !DBC
-  return program_counter;
 }
 
 
@@ -281,14 +289,18 @@ static void JumpToExceptionHandler(Thread* thread,
   thread->set_resume_pc(remapped_pc);
   uword run_exception_pc = StubCode::RunExceptionHandler_entry()->EntryPoint();
   Exceptions::JumpToFrame(thread, run_exception_pc, stack_pointer,
-                          frame_pointer);
+                          frame_pointer, false /* do not clear deopt */);
 }
 
 
 void Exceptions::JumpToFrame(Thread* thread,
                              uword program_counter,
                              uword stack_pointer,
-                             uword frame_pointer) {
+                             uword frame_pointer,
+                             bool clear_deopt_at_target) {
+  uword fp_for_clearing =
+      (clear_deopt_at_target ? frame_pointer + 1 : frame_pointer);
+  ClearLazyDeopts(thread, fp_for_clearing);
 #if defined(USING_SIMULATOR)
   // Unwinding of the C++ frames and destroying of their stack resources is done
   // by the simulator, because the target stack_pointer is a simulated stack

runtime/vm/exceptions.h

@@ -83,7 +83,8 @@ class Exceptions : AllStatic {
   static void JumpToFrame(Thread* thread,
                           uword program_counter,
                           uword stack_pointer,
-                          uword frame_pointer);
+                          uword frame_pointer,
+                          bool clear_deopt_at_target);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Exceptions);

runtime/vm/flow_graph_compiler.cc

@@ -1271,6 +1271,7 @@ void FlowGraphCompiler::GenerateStaticCall(intptr_t deopt_id,
                                    kNumArgsChecked)
               ->raw();
     }
+    AddCurrentDescriptor(RawPcDescriptors::kRewind, deopt_id, token_pos);
     EmitUnoptimizedStaticCall(argument_count, deopt_id, token_pos, locs,
                               call_ic_data);
   }

runtime/vm/intermediate_language.cc

@@ -3075,6 +3075,8 @@ void InstanceCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   } else {
     // Unoptimized code.
     ASSERT(!HasICData());
+    compiler->AddCurrentDescriptor(RawPcDescriptors::kRewind, deopt_id(),
+                                   token_pos());
     bool is_smi_two_args_op = false;
     const StubEntry* stub_entry = TwoArgsSmiOpInlineCacheEntry(token_kind());
     if (stub_entry != NULL) {

runtime/vm/json_stream.cc

@@ -139,6 +139,8 @@ static const char* GetJSONRpcErrorMessage(intptr_t code) {
       return "Isolate must be runnable";
     case kIsolateMustBePaused:
       return "Isolate must be paused";
+    case kCannotResume:
+      return "Cannot resume execution";
     case kIsolateIsReloading:
       return "Isolate is reloading";
     case kFileSystemAlreadyExists:

runtime/vm/json_stream.h

@@ -53,6 +53,7 @@ enum JSONRpcErrorCode {
   kStreamNotSubscribed = 104,
   kIsolateMustBeRunnable = 105,
   kIsolateMustBePaused = 106,
+  kCannotResume = 107,
 
   // Experimental (used in private rpcs).
   kIsolateIsReloading = 1000,

runtime/vm/object.cc

@@ -11700,6 +11700,8 @@ const char* PcDescriptors::KindAsStr(RawPcDescriptors::Kind kind) {
       return "runtime-call ";
     case RawPcDescriptors::kOsrEntry:
       return "osr-entry    ";
+    case RawPcDescriptors::kRewind:
+      return "rewind       ";
     case RawPcDescriptors::kOther:
       return "other        ";
     case RawPcDescriptors::kAnyKind:

runtime/vm/raw_object.h

@@ -1202,7 +1202,8 @@ class RawPcDescriptors : public RawObject {
     kUnoptStaticCall = kIcCall << 1,       // Call to a known target via stub.
     kRuntimeCall = kUnoptStaticCall << 1,  // Runtime call.
     kOsrEntry = kRuntimeCall << 1,         // OSR entry point in unopt. code.
-    kOther = kOsrEntry << 1,
+    kRewind = kOsrEntry << 1,              // Call rewind target address.
+    kOther = kRewind << 1,
     kLastKind = kOther,
     kAnyKind = -1
   };

runtime/vm/runtime_entry_list.h

@@ -40,6 +40,7 @@ namespace dart {
   V(TraceFunctionEntry)                                                        \
   V(TraceFunctionExit)                                                         \
   V(DeoptimizeMaterialize)                                                     \
+  V(RewindPostDeopt)                                                           \
   V(UpdateFieldCid)                                                            \
   V(InitStaticField)                                                           \
   V(GrowRegExpStack)                                                           \

runtime/vm/service.cc

@@ -2988,18 +2988,57 @@ static bool GetVMTimeline(Thread* thread, JSONStream* js) {
 }
 
 
+static const char* const step_enum_names[] = {
+    "None", "Into", "Over", "Out", "Rewind", "OverAsyncSuspension", NULL,
+};
+
+
+static const Debugger::ResumeAction step_enum_values[] = {
+    Debugger::kContinue,   Debugger::kStepInto,
+    Debugger::kStepOver,   Debugger::kStepOut,
+    Debugger::kStepRewind, Debugger::kStepOverAsyncSuspension,
+    Debugger::kContinue,  // Default value
+};
+
+
 static const MethodParameter* resume_params[] = {
-    RUNNABLE_ISOLATE_PARAMETER, NULL,
+    RUNNABLE_ISOLATE_PARAMETER,
+    new EnumParameter("step", false, step_enum_names),
+    new UIntParameter("frameIndex", false), NULL,
 };
 
 
 static bool Resume(Thread* thread, JSONStream* js) {
   const char* step_param = js->LookupParam("step");
+  Debugger::ResumeAction step = Debugger::kContinue;
+  if (step_param != NULL) {
+    step = EnumMapper(step_param, step_enum_names, step_enum_values);
+  }
+#if defined(TARGET_ARCH_DBC)
+  if (step == Debugger::kStepRewind) {
+    js->PrintError(kCannotResume,
+                   "Rewind not yet implemented on this architecture");
+    return true;
+  }
+#endif
+  intptr_t frame_index = 1;
+  const char* frame_index_param = js->LookupParam("frameIndex");
+  if (frame_index_param != NULL) {
+    if (step != Debugger::kStepRewind) {
+      // Only rewind supports the frameIndex parameter.
+      js->PrintError(
+          kInvalidParams,
+          "%s: the 'frameIndex' parameter can only be used when rewinding",
+          js->method());
+      return true;
+    }
+    frame_index = UIntParameter::Parse(js->LookupParam("frameIndex"));
+  }
   Isolate* isolate = thread->isolate();
   if (isolate->message_handler()->is_paused_on_start()) {
     // If the user is issuing a 'Over' or an 'Out' step, that is the
     // same as a regular resume request.
-    if ((step_param != NULL) && (strcmp(step_param, "Into") == 0)) {
+    if (step == Debugger::kStepInto) {
       isolate->debugger()->EnterSingleStepMode();
     }
     isolate->message_handler()->set_should_pause_on_start(false);
@@ -3028,31 +3067,18 @@ static bool Resume(Thread* thread, JSONStream* js) {
     PrintSuccess(js);
     return true;
   }
-  if (isolate->debugger()->PauseEvent() != NULL) {
+  if (isolate->debugger()->PauseEvent() == NULL) {
-    if (step_param != NULL) {
+    js->PrintError(kIsolateMustBePaused, NULL);
-      if (strcmp(step_param, "Into") == 0) {
-        isolate->debugger()->SetSingleStep();
-      } else if (strcmp(step_param, "Over") == 0) {
-        isolate->debugger()->SetStepOver();
-      } else if (strcmp(step_param, "Out") == 0) {
-        isolate->debugger()->SetStepOut();
-      } else if (strcmp(step_param, "OverAsyncSuspension") == 0) {
-        if (!isolate->debugger()->SetupStepOverAsyncSuspension()) {
-          js->PrintError(kInvalidParams,
-                         "Isolate must be paused at an async suspension point");
-          return true;
-        }
-      } else {
-        PrintInvalidParamError(js, "step");
-        return true;
-      }
-    }
-    isolate->SetResumeRequest();
-    PrintSuccess(js);
     return true;
   }
 
-  js->PrintError(kIsolateMustBePaused, NULL);
+  const char* error = NULL;
+  if (!isolate->debugger()->SetResumeAction(step, frame_index, &error)) {
+    js->PrintError(kCannotResume, error);
+    return true;
+  }
+  isolate->SetResumeRequest();
+  PrintSuccess(js);
   return true;
 }
 

runtime/vm/simulator_dbc.cc

@@ -3715,14 +3715,25 @@ void Simulator::JumpToFrame(uword pc, uword sp, uword fp, Thread* thread) {
   fp_ = reinterpret_cast<RawObject**>(fp);
 
   if (pc == StubCode::RunExceptionHandler_entry()->EntryPoint()) {
-    // Instead of executing the RunException stub, we implement its
+    // The RunExceptionHandler stub is a placeholder.  We implement
-    // behavior here.
+    // its behavior here.
     RawObject* raw_exception = thread->active_exception();
     RawObject* raw_stacktrace = thread->active_stacktrace();
     ASSERT(raw_exception != Object::null());
     special_[kExceptionSpecialIndex] = raw_exception;
     special_[kStacktraceSpecialIndex] = raw_stacktrace;
     pc_ = thread->resume_pc();
+  } else if (pc == StubCode::DeoptForRewind_entry()->EntryPoint()) {
+    // The DeoptForRewind stub is a placeholder.  We will eventually
+    // implement its behavior here.
+    //
+    // TODO(turnidge): Refactor the Deopt bytecode so that we can use
+    // the implementation here too.  The deopt pc is stored in
+    // Thread::resume_pc().  After invoking deoptimization, we usually
+    // call into Debugger::RewindPostDeopt(), but I need to figure out
+    // if that makes any sense (it would JumpToFrame during a
+    // JumpToFrame, which seems wrong).
+    UNIMPLEMENTED();
   } else {
     pc_ = pc;
   }

runtime/vm/stub_code.h

@@ -27,6 +27,7 @@ class Deserializer;
   V(GetStackPointer)                                                           \
   V(JumpToFrame)                                                               \
   V(RunExceptionHandler)                                                       \
+  V(DeoptForRewind)                                                            \
   V(UpdateStoreBuffer)                                                         \
   V(PrintStopMessage)                                                          \
   V(CallToRuntime)                                                             \
@@ -75,6 +76,7 @@ class Deserializer;
   V(LazyCompile)                                                               \
   V(OptimizeFunction)                                                          \
   V(RunExceptionHandler)                                                       \
+  V(DeoptForRewind)                                                            \
   V(FixCallersTarget)                                                          \
   V(Deoptimize)                                                                \
   V(DeoptimizeLazyFromReturn)                                                  \
@@ -195,6 +197,12 @@ class StubCode : public AllStatic {
 
 enum DeoptStubKind { kLazyDeoptFromReturn, kLazyDeoptFromThrow, kEagerDeopt };
 
+// Zap value used to indicate unused CODE_REG in deopt.
+static const uword kZapCodeReg = 0xf1f1f1f1;
+
+// Zap value used to indicate unused return address in deopt.
+static const uword kZapReturnAddress = 0xe1e1e1e1;
+
 }  // namespace dart
 
 #endif  // RUNTIME_VM_STUB_CODE_H_

runtime/vm/stub_code_arm.cc

@@ -537,19 +537,20 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   __ LeaveStubFrame();
   // Remove materialization arguments.
   __ add(SP, SP, Operand(R2, ASR, kSmiTagSize));
-  __ Ret();
+  // The caller is responsible for emitting the return instruction.
 }
 
 
 // R0: result, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ LoadImmediate(IP, 0xf1f1f1f1);
+  __ LoadImmediate(IP, kZapCodeReg);
   __ Push(IP);
   // Return address for "call" to deopt stub.
-  __ LoadImmediate(LR, 0xe1e1e1e1);
+  __ LoadImmediate(LR, kZapReturnAddress);
   __ ldr(CODE_REG, Address(THR, Thread::lazy_deopt_from_return_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
+  __ Ret();
 }
 
 
@@ -557,17 +558,19 @@ void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
 // R1: stacktrace, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ LoadImmediate(IP, 0xf1f1f1f1);
+  __ LoadImmediate(IP, kZapCodeReg);
   __ Push(IP);
   // Return address for "call" to deopt stub.
-  __ LoadImmediate(LR, 0xe1e1e1e1);
+  __ LoadImmediate(LR, kZapReturnAddress);
   __ ldr(CODE_REG, Address(THR, Thread::lazy_deopt_from_throw_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
+  __ Ret();
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+  __ Ret();
 }
 
 
@@ -1899,6 +1902,26 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Deoptimize a frame on the call stack before rewinding.
+// The arguments are stored in the Thread object.
+// No result.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  // Push zap value instead of CODE_REG.
+  __ LoadImmediate(IP, kZapCodeReg);
+  __ Push(IP);
+
+  // Load the deopt pc into LR.
+  __ LoadFromOffset(kWord, LR, THR, Thread::resume_pc_offset());
+  GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+
+  // After we have deoptimized, jump to the correct frame.
+  __ EnterStubFrame();
+  __ CallRuntime(kRewindPostDeoptRuntimeEntry, 0);
+  __ LeaveStubFrame();
+  __ bkpt(0);
+}
+
+
 // Calls to the runtime to optimize the given function.
 // R8: function to be reoptimized.
 // R4: argument descriptor (preserved).

runtime/vm/stub_code_arm64.cc

@@ -558,19 +558,20 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   __ LeaveStubFrame();
   // Remove materialization arguments.
   __ add(SP, SP, Operand(R2));
-  __ ret();
+  // The caller is responsible for emitting the return instruction.
 }
 
 
 // R0: result, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ LoadImmediate(TMP, 0xf1f1f1f1);
+  __ LoadImmediate(TMP, kZapCodeReg);
   __ Push(TMP);
   // Return address for "call" to deopt stub.
-  __ LoadImmediate(LR, 0xe1e1e1e1);
+  __ LoadImmediate(LR, kZapReturnAddress);
   __ ldr(CODE_REG, Address(THR, Thread::lazy_deopt_from_return_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
+  __ ret();
 }
 
 
@@ -578,17 +579,19 @@ void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
 // R1: stacktrace, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ LoadImmediate(TMP, 0xf1f1f1f1);
+  __ LoadImmediate(TMP, kZapCodeReg);
   __ Push(TMP);
   // Return address for "call" to deopt stub.
-  __ LoadImmediate(LR, 0xe1e1e1e1);
+  __ LoadImmediate(LR, kZapReturnAddress);
   __ ldr(CODE_REG, Address(THR, Thread::lazy_deopt_from_throw_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
+  __ ret();
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+  __ ret();
 }
 
 
@@ -1949,6 +1952,26 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Deoptimize a frame on the call stack before rewinding.
+// The arguments are stored in the Thread object.
+// No result.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  // Push zap value instead of CODE_REG.
+  __ LoadImmediate(TMP, kZapCodeReg);
+  __ Push(TMP);
+
+  // Load the deopt pc into LR.
+  __ LoadFromOffset(LR, THR, Thread::resume_pc_offset());
+  GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+
+  // After we have deoptimized, jump to the correct frame.
+  __ EnterStubFrame();
+  __ CallRuntime(kRewindPostDeoptRuntimeEntry, 0);
+  __ LeaveStubFrame();
+  __ brk(0);
+}
+
+
 // Calls to the runtime to optimize the given function.
 // R6: function to be re-optimized.
 // R4: argument descriptor (preserved).

runtime/vm/stub_code_dbc.cc

@@ -47,6 +47,12 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Not executed, but used as a sentinel in Simulator::JumpToFrame.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  __ Trap();
+}
+
+
 // TODO(vegorov) Don't generate this stub.
 void StubCode::GenerateFixCallersTargetStub(Assembler* assembler) {
   __ Trap();

runtime/vm/stub_code_ia32.cc

@@ -351,8 +351,6 @@ static void PushArgumentsArray(Assembler* assembler) {
 //   +------------------+
 //   | return-address   |  (deoptimization point)
 //   +------------------+
-//   | Saved CODE_REG   |
-//   +------------------+
 //   | ...              | <- SP of optimized frame
 //
 // Parts of the code cannot GC, part of the code can GC.
@@ -462,15 +460,16 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   __ popl(ECX);       // Pop return address.
   __ addl(ESP, EBX);  // Remove materialization arguments.
   __ pushl(ECX);      // Push return address.
-  __ ret();
+  // The caller is responsible for emitting the return instruction.
 }
 
 
 // EAX: result, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
   // Return address for "call" to deopt stub.
-  __ pushl(Immediate(0xe1e1e1e1));
+  __ pushl(Immediate(kZapReturnAddress));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
+  __ ret();
 }
 
 
@@ -478,13 +477,15 @@ void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
 // EDX: stacktrace, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
   // Return address for "call" to deopt stub.
-  __ pushl(Immediate(0xe1e1e1e1));
+  __ pushl(Immediate(kZapReturnAddress));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
+  __ ret();
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+  __ ret();
 }
 
 
@@ -1835,6 +1836,22 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Deoptimize a frame on the call stack before rewinding.
+// The arguments are stored in the Thread object.
+// No result.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  // Push the deopt pc.
+  __ pushl(Address(THR, Thread::resume_pc_offset()));
+  GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+
+  // After we have deoptimized, jump to the correct frame.
+  __ EnterStubFrame();
+  __ CallRuntime(kRewindPostDeoptRuntimeEntry, 0);
+  __ LeaveFrame();
+  __ int3();
+}
+
+
 // Calls to the runtime to optimize the given function.
 // EBX: function to be reoptimized.
 // EDX: argument descriptor (preserved).

runtime/vm/stub_code_mips.cc

@@ -549,18 +549,19 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   // Remove materialization arguments.
   __ SmiUntag(T1);
   __ addu(SP, SP, T1);
-  __ Ret();
+  // The caller is responsible for emitting the return instruction.
 }
 
 // V0: result, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ LoadImmediate(TMP, 0xf1f1f1f1);
+  __ LoadImmediate(TMP, kZapCodeReg);
   __ Push(TMP);
   // Return address for "call" to deopt stub.
-  __ LoadImmediate(RA, 0xe1e1e1e1);
+  __ LoadImmediate(RA, kZapReturnAddress);
   __ lw(CODE_REG, Address(THR, Thread::lazy_deopt_from_return_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
+  __ Ret();
 }
 
 
@@ -568,17 +569,19 @@ void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
 // V1: stacktrace, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ LoadImmediate(TMP, 0xf1f1f1f1);
+  __ LoadImmediate(TMP, kZapCodeReg);
   __ Push(TMP);
   // Return address for "call" to deopt stub.
-  __ LoadImmediate(RA, 0xe1e1e1e1);
+  __ LoadImmediate(RA, kZapReturnAddress);
   __ lw(CODE_REG, Address(THR, Thread::lazy_deopt_from_throw_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
+  __ Ret();
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+  __ Ret();
 }
 
 
@@ -2028,6 +2031,26 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Deoptimize a frame on the call stack before rewinding.
+// The arguments are stored in the Thread object.
+// No result.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  // Push zap value instead of CODE_REG.
+  __ LoadImmediate(TMP, kZapCodeReg);
+  __ Push(TMP);
+
+  // Load the deopt pc into RA.
+  __ lw(RA, Address(THR, Thread::resume_pc_offset()));
+  GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+
+  // After we have deoptimized, jump to the correct frame.
+  __ EnterStubFrame();
+  __ CallRuntime(kRewindPostDeoptRuntimeEntry, 0);
+  __ LeaveStubFrame();
+  __ break_(0);
+}
+
+
 // Calls to the runtime to optimize the given function.
 // T0: function to be reoptimized.
 // S4: argument descriptor (preserved).

runtime/vm/stub_code_x64.cc

@@ -498,18 +498,19 @@ static void GenerateDeoptimizationSequence(Assembler* assembler,
   __ popq(RCX);       // Pop return address.
   __ addq(RSP, RBX);  // Remove materialization arguments.
   __ pushq(RCX);      // Push return address.
-  __ ret();
+  // The caller is responsible for emitting the return instruction.
 }
 
 
 // RAX: result, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ pushq(Immediate(0xf1f1f1f1));
+  __ pushq(Immediate(kZapCodeReg));
   // Return address for "call" to deopt stub.
-  __ pushq(Immediate(0xe1e1e1e1));
+  __ pushq(Immediate(kZapReturnAddress));
   __ movq(CODE_REG, Address(THR, Thread::lazy_deopt_from_return_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromReturn);
+  __ ret();
 }
 
 
@@ -517,16 +518,18 @@ void StubCode::GenerateDeoptimizeLazyFromReturnStub(Assembler* assembler) {
 // RDX: stacktrace, must be preserved
 void StubCode::GenerateDeoptimizeLazyFromThrowStub(Assembler* assembler) {
   // Push zap value instead of CODE_REG for lazy deopt.
-  __ pushq(Immediate(0xf1f1f1f1));
+  __ pushq(Immediate(kZapCodeReg));
   // Return address for "call" to deopt stub.
-  __ pushq(Immediate(0xe1e1e1e1));
+  __ pushq(Immediate(kZapReturnAddress));
   __ movq(CODE_REG, Address(THR, Thread::lazy_deopt_from_throw_stub_offset()));
   GenerateDeoptimizationSequence(assembler, kLazyDeoptFromThrow);
+  __ ret();
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+  __ ret();
 }
 
 
@@ -1891,6 +1894,25 @@ void StubCode::GenerateRunExceptionHandlerStub(Assembler* assembler) {
 }
 
 
+// Deoptimize a frame on the call stack before rewinding.
+// The arguments are stored in the Thread object.
+// No result.
+void StubCode::GenerateDeoptForRewindStub(Assembler* assembler) {
+  // Push zap value instead of CODE_REG.
+  __ pushq(Immediate(kZapCodeReg));
+
+  // Push the deopt pc.
+  __ pushq(Address(THR, Thread::resume_pc_offset()));
+  GenerateDeoptimizationSequence(assembler, kEagerDeopt);
+
+  // After we have deoptimized, jump to the correct frame.
+  __ EnterStubFrame();
+  __ CallRuntime(kRewindPostDeoptRuntimeEntry, 0);
+  __ LeaveStubFrame();
+  __ int3();
+}
+
+
 // Calls to the runtime to optimize the given function.
 // RDI: function to be reoptimized.
 // R10: argument descriptor (preserved).