[interpreter] Implement OSR graph construction from bytecode.

src/compiler/bytecode-graph-builder.cc

Index: src/compiler/bytecode-graph-builder.cc
diff --git a/src/compiler/bytecode-graph-builder.cc b/src/compiler/bytecode-graph-builder.cc
index 5d9b54853a19d78bf41bfe65ab9320ba04aa97b7..4179856f8a9ea25953205965db2585e97a1baafd 100644
--- a/src/compiler/bytecode-graph-builder.cc
+++ b/src/compiler/bytecode-graph-builder.cc
@@ -60,6 +60,7 @@ class BytecodeGraphBuilder::Environment : public ZoneObject {
   Environment* CopyForConditional() const;
   Environment* CopyForLoop();
   void Merge(Environment* other);
+  void PrepareForOsr();
 
  private:
   explicit Environment(const Environment* copy);
@@ -358,6 +359,33 @@ void BytecodeGraphBuilder::Environment::PrepareForLoop() {
   builder()->exit_controls_.push_back(terminate);
 }
 
+void BytecodeGraphBuilder::Environment::PrepareForOsr() {
+  DCHECK_EQ(IrOpcode::kLoop, GetControlDependency()->opcode());
+  Node* start = graph()->start();
+
+  // Create a control node for the OSR entry point and merge it into the loop
+  // header. Update the current environment's control dependency accordingly.
+  Node* entry = graph()->NewNode(common()->OsrLoopEntry(), start, start);

[Jarin, 2016/07/26 14:46:36]

Could we possibly DCHECK that the control dependency has one input at this point
to make sure that the shape is what turbofan osr deconstruction expects?
(Possibly also that the existing input is OsrNormalEntry.)

[Michael Starzinger, 2016/07/26 14:58:51]

Done. The first invariant yes, I added a check of the input count. The second
suggestion however will most likely not hold. The "normal entry" is right after
start. There will be other control between the start and the loop. All we can
guarantee is that the "normal entry" should control-dominate the first loop
entry, but that is hard to verify in a check.

+  Node* control = builder()->MergeControl(GetControlDependency(), entry);
+  UpdateControlDependency(control);
+
+  // Create a merge of the effect from the OSR entry and the existing effect
+  // dependency. Update the current environment's effect dependency accordingly.
+  Node* effect = builder()->MergeEffect(GetEffectDependency(), entry, control);
+  UpdateEffectDependency(effect);
+
+  // Rename all values in the environment which will extend or introduce Phi
+  // nodes to contain the OSR values available at the entry point.
+  Node* osr_context = graph()->NewNode(
+      common()->OsrValue(Linkage::kOsrContextSpillSlotIndex), entry);
+  context_ = builder()->MergeValue(context_, osr_context, control);
+  for (size_t i = 0; i < values_.size(); i++) {
+    int index =
+        static_cast<int>(i) + InterpreterFrameConstants::kExtraSlotCount;
+    Node* osr_value = graph()->NewNode(common()->OsrValue(index), entry);
+    values_[i] = builder()->MergeValue(values_[i], osr_value, control);
+  }
+}
 
 bool BytecodeGraphBuilder::Environment::StateValuesRequireUpdate(
     Node** state_values, int offset, int count) {
@@ -447,6 +475,7 @@ BytecodeGraphBuilder::BytecodeGraphBuilder(Zone* local_zone,
           FrameStateType::kInterpretedFunction,
           bytecode_array()->parameter_count(),
           bytecode_array()->register_count(), info->shared_info())),
+      osr_ast_id_(info->osr_ast_id()),
       merge_environments_(local_zone),
       exception_handlers_(local_zone),
       current_exception_handler_(0),
@@ -521,6 +550,10 @@ bool BytecodeGraphBuilder::CreateGraph() {
                   GetFunctionContext());
   set_environment(&env);
 
+  // For OSR add an {OsrNormalEntry} as the start of the top-level environment.
+  // It will be replaced with {Dead} after typing and optimizations.
+  if (!osr_ast_id_.IsNone()) NewNode(common()->OsrNormalEntry());
+
   VisitBytecodes();
 
   // Finish the basic structure of the graph.
@@ -1393,8 +1426,12 @@ void BytecodeGraphBuilder::VisitStackCheck() {
 }
 
 void BytecodeGraphBuilder::VisitOsrPoll() {
-  // TODO(4764): Implement OSR graph construction. Not marked UNIMPLEMENTED to
-  // ensure the --ignition-osr flag can already be fuzzed without crashing.
+  // TODO(4764): This should be moved into the {VisitBytecodes} once we merge
+  // the polling with existing bytecode. This will also guarantee that we are
+  // not missing the OSR entry point, which we wouldn't catch right now.
+  if (osr_ast_id_.ToInt() == bytecode_iterator().current_offset()) {
+    environment()->PrepareForOsr();
+  }
 }
 
 void BytecodeGraphBuilder::VisitReturn() {