This fix has been checked in for both hs13 (snapshot for b03) and in hs14.
Add code to allocate extra space for java heap (either 1 page or alignment) and unprotect so that implicit null exceptions at heap_base + 1 page fault.
The ultimate fix should be in runtime, in the short term we may want to have some variant of -UseImplicitNullChecks for narrow oops in C2.
Implict null checks under CompressedOops are not triggering a change on control flow. It appears that the heap_base+1 page is still writeable, so the generated code does not SEGV as expected.