[runtime] Add PositiveNumberToUint32 helper to avoid double to uint roundtrip

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 11716 matching lines @@
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, receiver_string,
                                      Object::ToString(isolate, receiver));
 
   Handle<String> search_string;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, search_string,
                                      Object::ToString(isolate, search));
 
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, position,
                                      Object::ToInteger(isolate, position));
 
-  double index = std::max(position->Number(), 0.0);
-  index = std::min(index, static_cast<double>(receiver_string->length()));
-
-  return Smi::FromInt(String::IndexOf(isolate, receiver_string, search_string,
-                                      static_cast<uint32_t>(index)));
+  uint32_t index = receiver_string->ToValidIndex(*position);
+  return Smi::FromInt(
+      String::IndexOf(isolate, receiver_string, search_string, index));
 }
 
 namespace {
 
 template <typename T>
 int SearchString(Isolate* isolate, String::FlatContent receiver_content,
                  Vector<T> pat_vector, int start_index) {
   if (receiver_content.IsOneByte()) {
     return SearchString(isolate, receiver_content.ToOneByteVector(), pat_vector,
                         start_index);
@@ skipping 185 matching lines @@
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, position,
                                      Object::ToNumber(position));
 
   uint32_t start_index;
 
   if (position->IsNaN()) {
     start_index = receiver_string->length();
   } else {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, position,
                                        Object::ToInteger(isolate, position));
-
-    double position_number = std::max(position->Number(), 0.0);
-    position_number = std::min(position_number,
-                               static_cast<double>(receiver_string->length()));
-    start_index = static_cast<uint32_t>(position_number);
+    start_index = receiver_string->ToValidIndex(*position);
   }
 
   uint32_t pattern_length = search_string->length();
   uint32_t receiver_length = receiver_string->length();
 
   if (start_index + pattern_length > receiver_length) {
     start_index = receiver_length - pattern_length;
   }
 
   if (pattern_length == 0) {
@@ skipping 8449 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8