Fix issue 397 and issue 399.

src/runtime.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4137 matching lines @@
   CONVERT_DOUBLE_CHECKED(x, args[0]);
 
   // If the second argument is a smi, it is much faster to call the
   // custom powi() function than the generic pow().
   if (args[1]->IsSmi()) {
     int y = Smi::cast(args[1])->value();
     return Heap::AllocateHeapNumber(powi(x, y));
   }
 
   CONVERT_DOUBLE_CHECKED(y, args[1]);
-  if (y == 0.5) {
-    // It's not uncommon to use Math.pow(x, 0.5) to compute the square
-    // root of a number. To speed up such computations, we explictly
-    // check for this case and use the sqrt() function which is faster
-    // than pow().
-    return Heap::AllocateHeapNumber(sqrt(x));
-  } else if (y == -0.5) {
-    // Optimized using Math.pow(x, -0.5) == 1 / Math.pow(x, 0.5).
-    return Heap::AllocateHeapNumber(1.0 / sqrt(x));
-  } else if (y == 0) {
+
+  if (!isinf(x)) {
+    if (y == 0.5) {
+      // It's not uncommon to use Math.pow(x, 0.5) to compute the
+      // square root of a number. To speed up such computations, we
+      // explictly check for this case and use the sqrt() function
+      // which is faster than pow().
+      return Heap::AllocateHeapNumber(sqrt(x));
+    } else if (y == -0.5) {
+      // Optimized using Math.pow(x, -0.5) == 1 / Math.pow(x, 0.5).
+      return Heap::AllocateHeapNumber(1.0 / sqrt(x));
+    }
+  }
+
+  if (y == 0) {
     return Smi::FromInt(1);
   } else if (isnan(y) || ((x == 1 || x == -1) && isinf(y))) {
     return Heap::nan_value();
   } else {
     return Heap::AllocateHeapNumber(pow(x, y));
   }
 }
 
 
 static Object* Runtime_Math_round(Arguments args) {
@@ skipping 3378 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage();
   }
 }
 
 
 } }  // namespace v8::internal