RFR: 8255553: [PPC64] Introduce and use setbc and setnbc P10 instructions [v6]

[Martin Doerr]

On Thu, 5 Nov 2020 12:32:09 GMT, Ziviani <github.com+670087+jrziviani at openjdk.org> wrote:

>> src/hotspot/cpu/ppc/ppc.ad line 11422:
>> 
>>> 11420: 
>>> 11421: // Manifest a CmpL3 result in an integer register.
>>> 11422: instruct cmpL3_reg_reg(iRegIdst dst, iRegLsrc src1, iRegLsrc src2) %{
>> 
>> I had forgotten one detail in my previous review. Sorry for that. We need to model the CR0 effect:
>> instruct cmpL3_reg_reg(iRegIdst dst, iRegLsrc src1, iRegLsrc src2, flagsRegCR0 cr0) %{
>>   match(Set dst (CmpL3 src1 src2));
>>   effect(KILL cr0);
>> (Same for other nodes.)
>
> Wow, thanks for catching it. But, let me make my naive question: why is it necessary?

E.g. instruct testI_reg_imm sets cr0 as result and branchConFar uses it. The kill cr0 effect disallows scheduling your nodes between them.

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PR: https://git.openjdk.java.net/jdk/pull/907