RFR: 8307423: [s390x] Represent Registers as values

[Amit Kumar]

On Thu, 4 May 2023 19:46:52 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> The recent Register implementation uses wild pointer (including null pointer) dereferences which exhibit undefined behavior. We should migrate away from pointer-based representation of Register values as it was done for x86 ([JDK-8292153](https://bugs.openjdk.org/browse/JDK-8292153)). Problems exist when trying to build with GCC 11.3.0 ([JDK-8307093](https://bugs.openjdk.org/browse/JDK-8307093)).
>> 
>> Tested `fastdebug, slowdebug, optimized, release build` , `tier1-test` on fastdebug build and build with GCC-9.5.0 as well.
>
> src/hotspot/cpu/s390/assembler_s390.hpp line 196:
> 
>> 194:     _index(index),
>> 195:     _disp(disp) {}
>> 196: 
> 
> I can live with the removal, but I guess it may be useful at some point of time. s390 supports specifying both, index and disp (unlike PPC64).

This constructor was causing ambiguity with this one :

  Address(Register base, RegisterOrConstant roc, intptr_t disp = 0) :
    _base(base),
    _index(noreg),
    _disp(disp) {
    if (roc.is_constant()) _disp += roc.as_constant(); else _index = roc.as_register();
  }


that's why I removed it. But yeah I can try to find another workaround, any suggestion from your side ?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/13805#discussion_r1185639675