[runtime function] Fix IndexOf when start is -Infinity

src/runtime/runtime-array.cc

 // Copyright 2014 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/code-stubs.h"
 #include "src/conversions-inl.h"
 #include "src/elements.h"
@@ skipping 550 matching lines @@
   if (len == 0) return Smi::FromInt(-1);
 
   // Let n be ? ToInteger(fromIndex). (If fromIndex is undefined, this step
   // produces the value 0.)
   int64_t start_from;
   {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, from_index,
                                        Object::ToInteger(isolate, from_index));
     double fp = from_index->Number();
     if (fp > len) return Smi::FromInt(-1);
-    start_from = static_cast<int64_t>(fp);
+    if (V8_LIKELY(
+            fp >= static_cast<double>(std::numeric_limits<int64_t>::min()) &&
+            fp < static_cast<double>(std::numeric_limits<int64_t>::max()))) {

[Jakob Kummerow, 2017/05/09 11:03:32]

You don't need the second condition; the "fp > len" check above guarantees that
fp <= std::numeric_limits<int64_t>::max().

[predrag.rudic, 2017/05/09 12:43:08]

Acknowledged.

+      start_from = static_cast<int64_t>(fp);
+    } else {
+      start_from = fp < static_cast<double>(std::numeric_limits<int64_t>::min())

[Jakob Kummerow, 2017/05/09 11:03:32]

...and then you don't need a case distinction here either; always assigning
std::numeric_limits<int64_t>::min() is fine.

[predrag.rudic, 2017/05/09 12:43:07]

Acknowledged.

+                       ? std::numeric_limits<int64_t>::min()
+                       : std::numeric_limits<int64_t>::max();
+    }
   }
 
   int64_t index;
   if (start_from >= 0) {
     index = start_from;
   } else {
     index = len + start_from;
     if (index < 0) {
       index = 0;
     }
@@ skipping 76 matching lines @@
     DCHECK(accessor->HasElement(*spread_array, i));
     Handle<Object> element = accessor->Get(spread_array, i);
     result->set(i, *element);
   }
 
   return *result;
 }
 
 }  // namespace internal
 }  // namespace v8