[builtins] fix String.prototype.indexOf with negative indices

src/builtins/builtins-string.cc

Index: src/builtins/builtins-string.cc
diff --git a/src/builtins/builtins-string.cc b/src/builtins/builtins-string.cc
index 9ebd7cf0a79b3d5559407adf336ba6ae2de0905b..20ad423b144a5e0a12db3d9dc71a35d7cba2a547 100644
--- a/src/builtins/builtins-string.cc
+++ b/src/builtins/builtins-string.cc
@@ -832,7 +832,7 @@ void StringBuiltinsAssembler::StringIndexOf(
   GotoIf(IntPtrLessThan(IntPtrConstant(1), needle_length),
          &call_runtime_unchecked);
   Node* string_length = SmiUntag(LoadStringLength(receiver));
-  Node* start_position = SmiUntag(position);
+  Node* start_position = IntPtrMax(SmiUntag(position), IntPtrConstant(0));
 
   GotoIf(IntPtrEqual(IntPtrConstant(0), needle_length), &zero_length_needle);
   // Check that the needle fits in the start position.
@@ -940,7 +940,6 @@ TF_BUILTIN(StringPrototypeIndexOf, StringBuiltinsAssembler) {
     search_string.Bind(arguments.AtIndex(0));
     position.Bind(arguments.AtIndex(1));
     GotoUnless(TaggedIsSmi(position.value()), &call_runtime);
-    position.Bind(SmiMax(position.value(), SmiConstant(0)));
     Goto(&fast_path);
   }