src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp

rev 53052 : [mq]: asm.patch

@@ -964,5 +964,28 @@
     StubCodeGenerator cgen(&buf);
     _shenandoah_wb = generate_shenandoah_wb(&cgen, false, true);
     _shenandoah_wb_C = generate_shenandoah_wb(&cgen, true, !ShenandoahWriteBarrierCsetTestInIR);
   }
 }
+
+bool ShenandoahBarrierSetAssembler::needs_explicit_null_check(intptr_t offset) {
+  // Exception handler checks the nmethod's implicit null checks table
+  // only when this method returns false.
+#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();
+    int adj = BrooksPointer::byte_offset();
+    if ((uintptr_t)(offset - adj) >= base) {
+      // Normalize offset for the next check.
+      offset = (intptr_t)(pointer_delta((void*)offset, (void*)base, 1));
+    }
+  }
+#endif
+  if (offset == BrooksPointer::byte_offset()) {
+    return false;
+  }
+  return offset < 0 || os::vm_page_size() <= offset;
+}