249 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {

   250   // Exception handler checks the nmethod's implicit null checks table

   251   // only when this method returns false.

   252 #ifndef SPARC

   253   // Sparc does not have based addressing

   254   if (UseCompressedOops) {

   255     // The first page after heap_base is unmapped and

   256     // the 'offset' is equal to [heap_base + offset] for

   257     // narrow oop implicit null checks.

   258     uintptr_t heap_base = (uintptr_t)Universe::heap_base();

   259     if ((uintptr_t)offset >= heap_base) {

   260       // Normalize offset for the next check.

   261       offset = (intptr_t)(pointer_delta((void*)offset, (void*)heap_base, 1));

   262     }

   263   }

   264 #endif // SPARC

   265   return offset < 0 || os::vm_page_size() <= offset;

   266 }