RFR: JDK-8307349: Support xlc17 clang toolchain on AIX [v2]

[Matthias Baesken]

On Wed, 10 May 2023 13:59:15 GMT, JoKern65 <duke at openjdk.org> wrote:

>> The new xlc17 compiler should be supported to build OpenJDK on AIX. This compiler, compared to the currently supported xlc16, has a significantly more recent clang (xlc 17.1.1 uses clang 15) included.
>> 1. Because the frontend interface of the new compiler (c-flags, Ld-Flags) has changed from an xlc to a clang interface we decided to use the clang toolchain for the new xlc17 compiler.
>> 2. Unfortunately, the system headers are mainly unchanged, so they do not harmonize with the src/hotspot/share/utilities/globalDefinitions_gcc.hpp which would be used if we totally switch to clang toolchain. So we keep the HOTSPOT_TOOLCHAIN_TYPE=xlc
>> 3. In src/hotspot/share/utilities/globalDefinitions_xlc.hpp we introduce a new define AIX_XLC_GE_17 which is set if we build with the new xlc17 on AIX. This define will be used in following PRs.
>
> JoKern65 has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - revert accidantially changed mode bits
>  - I followed the proposals

Marked as reviewed by mbaesken (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/13898#pullrequestreview-1420735558