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

[Kim Barrett]

On Tue, 9 Apr 2024 19:20:22 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Joachim Kern has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   version check not needed anymore
>
> src/hotspot/share/utilities/globalDefinitions_gcc.hpp line 36:
> 
>> 34: #if defined(_AIX)
>> 35: #include <alloca.h>
>> 36: #endif
> 
> I would much rather see this include added in the few places it was actually needed, rather than being
> added here.

Do we even need to include <alloca.h>? 

>From the Linux man page for alloca:

By necessity, alloca() is a compiler built-in, also known as
__builtin_alloca().  By default, modern compilers automatically
translate all uses of alloca() into the built-in, but this is
forbidden if standards conformance is requested (-ansi, -std=c*),
in which case <alloca.h> is required, lest a symbol dependency be
emitted.

There are uses of it in shared code where there isn't an applicable include,
other than from globalDefinitions_xlc.hpp. So it appears all other supported
compilers do treat it as a built-in with the options we are providing, and
don't need the include. Maybe that's true for the new xlc compiler too?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18536#discussion_r1558565268