acmp have to perform nullcheck for both arguments (in Valhalla).
Right now a very nice hack is used:
    // might be substitutable, test if either rax or rdx is null
    __ testptr(rdx, rax);
    __ jcc(Assembler::zero, (cc == equal) ? not_taken : taken);

Unfortunately, that hack is valid only if Universe::_verify_oop_bits is not zero.
TemplateTable should check if Universe::_verify_oop_bits is zero and generates two null checks in that case.
 
see discussion: https://mail.openjdk.java.net/pipermail/valhalla-dev/2020-November/008237.html