On Mon, 31 Jul 2023 09:51:44 GMT, sid8606 <d...@openjdk.org> wrote:
>> src/hotspot/cpu/s390/upcallLinker_s390.cpp line 45:
>>
>>> 43: if (reg == Z_SP) continue;
>>> 44: // though Z_R6 is argument register it is a saved register
>>> 45: if (!abi.is_volatile_reg(reg) || reg == Z_R6) {
>>
>> So, is the prior assumption that all argument registers are also volatile
>> incorrect?
>>
>> If so, I think it would be better to change `ABIDescriptor::is_volatile_reg`
>> ([1]) to only look at the `_integer_additional_volatile_registers` list
>> (maybe rename it too), and then list all the volatile regs in
>> LinuxS390CallArranger explicitly, excluding R6 ([2]). That way all the
>> information about which regs are volatile is in one place
>> (LinuxS390CallArranger).
>>
>> [1]:
>> https://github.com/openjdk/jdk/pull/14801/files#diff-7096e1975de20baa3219d616506f26ba2b4500bf5ad28c331e3d6049a32a461eR39-R42
>> [2]:
>> https://github.com/openjdk/jdk/pull/14801/files#diff-09da9016992b04bab73b6cc6aad8ca719e86c90c398af4e000583c1f8220a99bR73
>
> Yes, s390x ABI says R6 is an argument register as we as non-volatile register.
> It make sense, I'll make suggested changes.
Made the changes in new commit.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14801#discussion_r1279354543
