[debugger,compiler] do not recompile already compiled inner functions.

GetSharedFunctionInfo will compile inner functions if we get the
compile-eager hint, even if the shared function info already exists, and
the function already has been compiled. This breaks suspended generator
objects.

R=mstarzinger@chromium.org, neis@chromium.org
BUG=v8:5575

Review-Url: https://codereview.chromium.org/2494043002
Cr-Commit-Position: refs/heads/master@{#40936}

src/compiler.cc

@@ -1591,7 +1591,15 @@ Handle<SharedFunctionInfo> Compiler::GetSharedFunctionInfo(
   RuntimeCallTimerScope runtimeTimer(isolate, &RuntimeCallStats::CompileCode);
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"), "V8.CompileCode");
 
-  if (!literal->ShouldEagerCompile()) {
+  if (result->is_compiled()) {
+    // If this inner function is already compiled, we don't need to compile
+    // again. When compiling for debug, we are not interested in having debug
+    // break slots in inner functions, neither for setting break points nor
+    // for revealing inner functions.
+    // This is especially important for generators. We must not replace the
+    // code for generators, as there may be suspended generator objects.
+    return result;
+  } else if (!literal->ShouldEagerCompile()) {
     info.SetCode(isolate->builtins()->CompileLazy());
     Scope* outer_scope = literal->scope()->GetOuterScopeWithContext();
     if (outer_scope) {

test/debugger/regress/regress-5575-1.js

+// Copyright 2016 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.
+
+Debug = debug.Debug;
+
+Debug.setListener(function() {});
+
+function factory() {
+  return function* generator() {
+    debugger;
+    yield 42;
+  }
+}
+
+Debug.setBreakPoint(function(){}, 0, 0);
+var generator = factory();
+var obj = generator();
+obj.next();
+Debug.setBreakPoint(factory, 0, 0);
+obj.next();

test/debugger/regress/regress-5575-2.js

+// Copyright 2016 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.
+
+Debug = debug.Debug;
+
+Debug.setListener(function() {});
+
+function main() {
+  function* boo() {
+    debugger;
+    yield 42;
+  }
+
+  var gen = boo();
+  gen.next();
+  Debug.setBreakPoint(main, 0, 0);
+  gen.next();
+}
+
+main();

test/debugger/regress/regress-5575-3.js

+// Copyright 2016 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.
+
+Debug = debug.Debug;
+
+let n = 0;
+function listener(event, exec_state, event_data, data) {
+  if (event == Debug.DebugEvent.Break) {
+    if (n++ == 0) {
+      Debug.setBreakPoint(main, 0, 0);
+    }
+  }
+}
+
+Debug.setListener(listener);
+
+function main() {
+  function* boo() {
+    debugger;
+    yield;
+  }
+
+  var gen = boo();
+  gen.next();
+  gen.next();
+}
+
+main();