RFR: 8331126: [s390x] secondary_super_cache does not scale well [v4]

[Martin Doerr]

On Tue, 25 Jun 2024 13:30:37 GMT, Lutz Schmidt <lucy at openjdk.org> wrote:

>> src/hotspot/cpu/s390/macroAssembler_s390.cpp line 3171:
>> 
>>> 3169: 
>>> 3170:   bind(L_loop);
>>> 3171:   z_cg(r_value, Address(r_addr));
>> 
>> Idea: I think it is possible to use z_xg to do both at once: Set to 0 iff equal and CC to equal. (Like PPC64.)
>
> Good idea. But will have no benefit. When using z_xg, r_value will be altered. Subsequent iterations will then compare against a modified value. To use the triadic register instruction (XGRK), we first have to load the value int a scratch register.

Ok. So, maybe better keep it as it is.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/19544#discussion_r1652921950