[turbofan] Introduce dedicated StringIndexOf operator.

src/compiler/effect-control-linearizer.cc

Index: src/compiler/effect-control-linearizer.cc
diff --git a/src/compiler/effect-control-linearizer.cc b/src/compiler/effect-control-linearizer.cc
index 1c882517970b89d03d8bf4a4e2fd978b2dc8705b..bc24a30968f5671c31d38fb928a128e77153c93d 100644
--- a/src/compiler/effect-control-linearizer.cc
+++ b/src/compiler/effect-control-linearizer.cc
@@ -750,6 +750,9 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
     case IrOpcode::kStringFromCodePoint:
       result = LowerStringFromCodePoint(node);
       break;
+    case IrOpcode::kStringIndexOf:
+      result = LowerStringIndexOf(node);
+      break;
     case IrOpcode::kStringCharAt:
       result = LowerStringCharAt(node);
       break;
@@ -2056,6 +2059,20 @@ Node* EffectControlLinearizer::LowerStringFromCodePoint(Node* node) {
   return done.PhiAt(0);
 }
 
+Node* EffectControlLinearizer::LowerStringIndexOf(Node* node) {
+  Node* subject = node->InputAt(0);
+  Node* search_string = node->InputAt(1);
+  Node* position = node->InputAt(2);
+
+  Callable callable = CodeFactory::StringIndexOf(isolate());
+  Operator::Properties properties = Operator::kEliminatable;
+  CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
+  CallDescriptor* desc = Linkage::GetStubCallDescriptor(
+      isolate(), graph()->zone(), callable.descriptor(), 0, flags, properties);
+  return __ Call(desc, __ HeapConstant(callable.code()), subject, search_string,
+                 position, __ NoContextConstant());
+}
+
 Node* EffectControlLinearizer::LowerStringComparison(Callable const& callable,
                                                      Node* node) {
   Node* lhs = node->InputAt(0);