[turbofan] Introduce TruncateTaggedToWord32 simplified operator.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index d910c01101d3879a015f211492d66a4dc1e8af3f..f67068c7077736842d1c47fd73febe912461630f 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -5221,7 +5221,7 @@ compiler::Node* ConvertTaggedAtomicIndexToWord32(CodeStubAssembler* a,
   a->Bind(&if_numberisnotsmi);
   {
     Node* number_index_value = a->LoadHeapNumberValue(number_index);
-    Node* access_index = a->TruncateFloat64ToInt32(number_index_value);
+    Node* access_index = a->TruncateFloat64ToWord32(number_index_value);
     Node* test_index = a->ChangeInt32ToFloat64(access_index);
 
     CodeStubAssembler::Label if_indexesareequal(a), if_indexesarenotequal(a);