[turbofan] Stay in optimized code for SMI inputs to %_ToInteger.

src/compiler/js-intrinsic-lowering.cc

Index: src/compiler/js-intrinsic-lowering.cc
diff --git a/src/compiler/js-intrinsic-lowering.cc b/src/compiler/js-intrinsic-lowering.cc
index ca5cb932b4bd7606521b32ae63c7c8076779d74f..2d5c0c77a7e64b8705a80ee43c87b946edc61af0 100644
--- a/src/compiler/js-intrinsic-lowering.cc
+++ b/src/compiler/js-intrinsic-lowering.cc
@@ -507,12 +507,43 @@ Reduction JSIntrinsicLowering::ReduceSubString(Node* node) {
 
 Reduction JSIntrinsicLowering::ReduceToInteger(Node* node) {
   Node* value = NodeProperties::GetValueInput(node, 0);
+  Node* context = NodeProperties::GetContextInput(node);
+  Node* frame_state = NodeProperties::GetFrameStateInput(node, 0);
+  Node* effect = NodeProperties::GetEffectInput(node);
+  Node* control = NodeProperties::GetControlInput(node);
+
+  // ToInteger is a no-op on integer values and -0.
   Type* value_type = NodeProperties::GetType(value);
   if (value_type->Is(type_cache().kIntegerOrMinusZero)) {
     ReplaceWithValue(node, value);
     return Replace(value);
   }
-  return NoChange();
+
+  Node* check = graph()->NewNode(simplified()->ObjectIsSmi(), value);
+  Node* branch =
+      graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control);
+
+  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+  Node* etrue = effect;
+  Node* vtrue = value;
+
+  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+  Node* efalse = effect;
+  Node* vfalse;
+  {
+    vfalse = efalse =
+        graph()->NewNode(javascript()->CallRuntime(Runtime::kToInteger), value,
+                         context, frame_state, efalse, if_false);
+    if_false = graph()->NewNode(common()->IfSuccess(), vfalse);
+  }
+
+  control = graph()->NewNode(common()->Merge(2), if_true, if_false);
+  effect = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, control);
+  value = graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
+                           vtrue, vfalse, control);
+  // TODO(bmeurer, mstarzinger): Rewire IfException inputs to {vfalse}.
+  ReplaceWithValue(node, value, effect, control);
+  return Changed(value);
 }