RFR: JDK-8306304: Fix xlc17 clang warnings in ppc and aix code [v2]

[JoKern65]

On Fri, 12 May 2023 21:56:50 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> JoKern65 has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   cosmetic changes
>
> src/hotspot/cpu/ppc/ppc.ad line 11444:
> 
>> 11442:   effect(KILL cr0);
>> 11443:   ins_cost(DEFAULT_COST * 5);
>> 11444:   size((VM_Version::has_brw() ? 16 : 20));
> 
> What is it complaining about here?

/data/d042520/xlc17/jdk/src/hotspot/cpu/ppc/c1_LIRGenerator_ppc.cpp:426:97: error: shifting a negative signed value is undefined [-Werror,-Wshift-negative-value]
I reverted my change in c1_LIRGenerator_ppc.cpp and added shift-negative-value to the DISABLED_WARNINGS_clang in CompileJvm.gmk.

ad_ppc.cpp:18388:10: error: converting the result of '?:' with integer constants to a boolean always evaluates to 'true' [-Werror,-Wtautological-constant-compare]
  assert(VerifyOops || MachNode::size(ra_) <= VM_Version::has_brw() ? 16 : 20, "bad fixed size");
         ^
Should I also add tautological-constant-compare to DISABLED_WARNINGS_clang in CompileJvm.gmk or where else?

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PR Review Comment: https://git.openjdk.org/jdk/pull/13953#discussion_r1193506933