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

src/builtins/builtins-string.cc

 // Copyright 2016 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/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 #include "src/code-factory.h"
 #include "src/code-stub-assembler.h"
 #include "src/regexp/regexp-utils.h"
 
@@ skipping 743 matching lines @@
                                      Object::ToString(isolate, search));
 
   Handle<Object> position = args.atOrUndefined(isolate, 2);
   int end;
 
   if (position->IsUndefined(isolate)) {
     end = str->length();
   } else {
     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>(str->length()));
-    end = static_cast<uint32_t>(index);
+    end = str->ToValidIndex(*position);
   }
 
   int start = end - search_string->length();
   if (start < 0) return isolate->heap()->false_value();
 
   str = String::Flatten(str);
   search_string = String::Flatten(search_string);
 
   DisallowHeapAllocation no_gc;  // ensure vectors stay valid
   String::FlatContent str_content = str->GetFlatContent();
@@ skipping 39 matching lines @@
                                   "String.prototype.includes")));
   }
   Handle<String> search_string;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, search_string,
                                      Object::ToString(isolate, search));
   Handle<Object> position;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, position,
       Object::ToInteger(isolate, args.atOrUndefined(isolate, 2)));
 
-  double index = std::max(position->Number(), 0.0);
-  index = std::min(index, static_cast<double>(str->length()));
-
-  int index_in_str = String::IndexOf(isolate, str, search_string,
-                                     static_cast<uint32_t>(index));
+  uint32_t index = str->ToValidIndex(*position);
+  int index_in_str = String::IndexOf(isolate, str, search_string, index);
   return *isolate->factory()->ToBoolean(index_in_str != -1);
 }
 
 // ES6 section 21.1.3.8 String.prototype.indexOf ( searchString [ , position ] )
 BUILTIN(StringPrototypeIndexOf) {
   HandleScope handle_scope(isolate);
 
   return String::IndexOf(isolate, args.receiver(),
                          args.atOrUndefined(isolate, 1),
                          args.atOrUndefined(isolate, 2));
@@ skipping 354 matching lines @@
                                      Object::ToString(isolate, search));
 
   Handle<Object> position = args.atOrUndefined(isolate, 2);
   int start;
 
   if (position->IsUndefined(isolate)) {
     start = 0;
   } else {
     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>(str->length()));
-    start = static_cast<uint32_t>(index);
+    start = str->ToValidIndex(*position);
   }
 
   if (start + search_string->length() > str->length()) {
     return isolate->heap()->false_value();
   }
 
   FlatStringReader str_reader(isolate, String::Flatten(str));
   FlatStringReader search_reader(isolate, String::Flatten(search_string));
 
   for (int i = 0; i < search_string->length(); i++) {
@@ skipping 244 matching lines @@
         Runtime::kThrowIncompatibleMethodReceiver, context,
         assembler.HeapConstant(assembler.factory()->NewStringFromAsciiChecked(
             "String Iterator.prototype.next", TENURED)),
         iterator);
     assembler.Return(result);  // Never reached.
   }
 }
 
 }  // namespace internal
 }  // namespace v8