Add test case for replacing turbofan code for debugging.

R=jarin@chromium.org
BUG=v8:3660
LOG=N

Review URL: https://codereview.chromium.org/665833003

Cr-Commit-Position: refs/heads/master@{#25002}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25002 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/debug-step-turbofan.js

@@ -0,0 +1,57 @@
+// Copyright 2014 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.
+
+// Flags: --turbo-filter=g --allow-natives-syntax
+
+// Test that Debug::PrepareForBreakPoints can deal with turbofan code (g)
+// on the stack.  Without deoptimization support, we will not be able to
+// replace optimized code for g by unoptimized code with debug break slots.
+// This would cause stepping to fail (V8 issue 3660).
+
+function f(x) {
+  g(x);
+  var a = 0;              // Break 6
+  return a;               // Break 7
+}                         // Break 8
+
+function g(x) {
+  if (x) h();
+  var a = 0;              // Break 2
+  var b = 1;              // Break 3
+  return a + b;           // Break 4
+}                         // Break 5
+
+function h() {
+  debugger;               // Break 0
+}                         // Break 1
+
+Debug = debug.Debug;
+var exception = null;
+var break_count = 0;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    exec_state.prepareStep(Debug.StepAction.StepNext, 1);
+    print(exec_state.frame(0).sourceLineText());
+    var match = exec_state.frame(0).sourceLineText().match(/Break (\d)/);
+    assertNotNull(match);
+    assertEquals(break_count++, parseInt(match[1]));
+  } catch (e) {
+    print(e + e.stack);
+    exception = e;
+  }
+}
+
+f(0);
+f(0);
+%OptimizeFunctionOnNextCall(g);
+
+Debug.setListener(listener);
+
+f(1);
+
+Debug.setListener(null);  // Break 9
+assertNull(exception);
+assertEquals(10, break_count);

test/mjsunit/mjsunit.status

@@ -81,6 +81,10 @@
   'compiler/osr-assert': [PASS, NO_VARIANTS],
   'regress/regress-2185-2': [PASS, NO_VARIANTS],
 
+  # Issue 3660: Replacing activated TurboFan frames by unoptimized code does
+  # not work, but we expect it to not crash.
+  'debug-step-turbofan': [PASS, FAIL],
+
   # Support for %GetFrameDetails is missing and requires checkpoints.
   'debug-evaluate-bool-constructor': [PASS, NO_VARIANTS],
   'debug-evaluate-const': [PASS, NO_VARIANTS],