RFR: 8329257: AIX: Switch HOTSPOT_TOOLCHAIN_TYPE from xlc to gcc [v3]

[Kim Barrett]

On Wed, 10 Apr 2024 14:19:59 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> When only looking at AIX code, I think the inclusion of alloca.h was cleaner. Agreed. The new code makes AIX behave like other platforms and avoids the AIX specific part in shared code.
>> I could live with either version.
>
> I can live with either, too.

That build failure in shared code does not happen with Xcode clang, gcc, or
Visual Studio, even though none of them appear to have a relevant define or
include. So the clang variant being used for AIX is different from the Xcode
clang variant (and maybe others) in its treatment of alloca. Weird!

I can also live with either the macro or the includes where needed.  I dislike
conditionally adding the include in globalDefinitions_gcc.hpp.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18536#discussion_r1560113548