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

[Kim Barrett]

On Fri, 12 May 2023 16:16:01 GMT, JoKern65 <duke at openjdk.org> wrote:

>> When using the new xlc17 compiler (based on a recent clang) to build OpenJDk on AIX , we run into various "warnings as errors".
>> Many of those are in the aix or ppc specific codebase and could be addressed by small adjustments.
>> A lot of those changes are in hotspot, some might be somewhere else in the OpenJDK C/C++ code.
>> With this PR we address only the platform dependent code changes.
>
> JoKern65 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   cosmetic changes

Changes requested by kbarrett (Reviewer).

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?

src/hotspot/os/aix/os_aix.cpp line 464:

> 462:       guarantee0(shmid != -1); // Should always work.
> 463:       // Try to set pagesize.
> 464:       struct shmid_ds shm_buf = { {0,0,0,0,0,0,0,0},0,0,0,0,0,0,0,0,0,0,0,0,0,0 };

Would just `= {};` work?  (I think it should, but with warnings who knows...)

src/java.desktop/aix/native/libawt/porting_aix.c line 49:

> 47:   for (;;) {
> 48:     if (addr >= p->ldinfo_textorg &&
> 49:         (char*)addr < (char*)(p->ldinfo_textorg) + p->ldinfo_textsize) {

What is being warned about here?  At worst, could you just cast the RHS to `void*`?

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PR Review: https://git.openjdk.org/jdk/pull/13953#pullrequestreview-1425195126
PR Review Comment: https://git.openjdk.org/jdk/pull/13953#discussion_r1192823550
PR Review Comment: https://git.openjdk.org/jdk/pull/13953#discussion_r1192824441
PR Review Comment: https://git.openjdk.org/jdk/pull/13953#discussion_r1192825686