src/hotspot/share/asm/assembler.cpp

 
 #include "precompiled.hpp"
 #include "asm/codeBuffer.hpp"
 #include "asm/macroAssembler.hpp"
 #include "asm/macroAssembler.inline.hpp"
+#include "gc/shared/collectedHeap.hpp"
 #include "runtime/atomic.hpp"
 #include "runtime/icache.hpp"
 #include "runtime/os.hpp"
 #include "runtime/thread.hpp"
 

@@ -305,23 +306,32
     return code_section()->outer()->code_string(str);
   }
   return NULL;
 }
 
-bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
+bool MacroAssembler::uses_implicit_null_check(void* address) {
   // Exception handler checks the nmethod's implicit null checks table
   // only when this method returns false.
+  intptr_t cell_header_size = Universe::heap()->cell_header_size();
+  size_t region_size = os::vm_page_size() + cell_header_size;
 #ifdef _LP64
   if (UseCompressedOops && Universe::narrow_oop_base() != NULL) {
-    assert (Universe::heap() != NULL, "java heap should be initialized");
     // The first page after heap_base is unmapped and
     // the 'offset' is equal to [heap_base + offset] for
     // narrow oop implicit null checks.
-    uintptr_t base = (uintptr_t)Universe::narrow_oop_base();
-    if ((uintptr_t)offset >= base) {
-      // Normalize offset for the next check.
-      offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1));
+    char* start = ((char*)Universe::narrow_oop_base()) - cell_header_size;
+    char* end = start + region_size;
+    if (address >= start && address < end) {
+      return true;
     }
   }
 #endif
-  return offset < 0 || os::vm_page_size() <= offset;
+  char* start = (char*)-cell_header_size;
+  char* end = start + region_size;
+  return address >= start && address < end;
+}
+
+bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
+  // Check if offset is outside of [-cell_header_size, os::vm_page_size)
+  return offset < -Universe::heap()->cell_header_size() ||
+         offset >= os::vm_page_size();
 }