Fixed power-of-2 predicates, excluding 0.

src/utils.h

 // Copyright 2012 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 25 matching lines @@
 #include "allocation.h"
 #include "checks.h"
 #include "globals.h"
 
 namespace v8 {
 namespace internal {
 
 // ----------------------------------------------------------------------------
 // General helper functions
 
-#define IS_POWER_OF_TWO(x) (((x) & ((x) - 1)) == 0)
+#define IS_POWER_OF_TWO(x) ((x) != 0 && (((x) & ((x) - 1)) == 0))
 
-// Returns true iff x is a power of 2 (or zero). Cannot be used with the
-// maximally negative value of the type T (the -1 overflows).
+// Returns true iff x is a power of 2. Cannot be used with the maximally
+// negative value of the type T (the -1 overflows).
 template <typename T>
 inline bool IsPowerOf2(T x) {
   return IS_POWER_OF_TWO(x);
 }
 
 
 // X must be a power of 2.  Returns the number of trailing zeros.
 inline int WhichPowerOf2(uint32_t x) {
   ASSERT(IsPowerOf2(x));
-  ASSERT(x != 0);
   int bits = 0;
 #ifdef DEBUG
   int original_x = x;
 #endif
   if (x >= 0x10000) {
     bits += 16;
     x >>= 16;
   }
   if (x >= 0x100) {
     bits += 8;
@@ skipping 1132 matching lines @@
   iterator end() { return container_->end(); }
   reverse_iterator rbegin() { return container_->rbegin(); }
   reverse_iterator rend() { return container_->rend(); }
  private:
   C* container_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_UTILS_H_