RFR : 8218136: minor hotspot adjustments for xlclang++ from xlc16 on AIX

[Lindenmaier, Goetz]

Hi Matthias, 

The demangle fix is kind of preliminary, but to get the compiler
working it is acceptable to skip this code for now.

The old xlc stuff is good to be removed. 
Could you please remove USE_XLC_PREFETCH_WRITE_BUILTIN
altogether and replace its only use by USE_XLC_BUILTINS?

Also, I think it makes sense to put 
  #if __IBMCPP__ < 1000
  #error "xlc < 10 not supported"
  #endif
into the file.

Probably we should even check for having at least xlc 12.

Best regards,
  Goetz.

> -----Original Message-----
> From: hotspot-dev <hotspot-dev-bounces at openjdk.java.net> On Behalf Of
> Baesken, Matthias
> Sent: Montag, 4. Februar 2019 12:36
> To: David Holmes <david.holmes at oracle.com>; 'hotspot-
> dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>;
> 'magnus.ihse.bursie at oracle.com' <magnus.ihse.bursie at oracle.com>
> Cc: 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>
> Subject: RE: RFR : 8218136: minor hotspot adjustments for xlclang++ from
> xlc16 on AIX
> 
> Hi  David,  I  want to follow your suggestion 😊 .
> I adjusted the comment , see  globalDefinitions_xlc.hpp  .
> 
> Additionally I removed a  strange ifdef  handling pre-xlc10 versions  that are
> not useful  today any more for OpenJDK
> ( we  most likely cannot build jdk/jdk  with xlc versions < 10).
> 
> New webrev :
> 
> http://cr.openjdk.java.net/~mbaesken/webrevs/8218136.2/
> 
> 
> Best regards, Matthias
> 
> 
> 
> > -----Original Message-----
> > From: David Holmes <david.holmes at oracle.com>
> > Sent: Freitag, 1. Februar 2019 13:49
> > To: Baesken, Matthias <matthias.baesken at sap.com>; 'hotspot-
> > dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>;
> > 'magnus.ihse.bursie at oracle.com' <magnus.ihse.bursie at oracle.com>
> > Cc: 'build-dev at openjdk.java.net' <build-dev at openjdk.java.net>
> > Subject: Re: RFR : 8218136: minor hotspot adjustments for xlclang++ from
> > xlc16 on AIX
> >
> > Hi Matthias,
> >
> > On 1/02/2019 10:36 pm, Baesken, Matthias wrote:
> > > New webrev :
> > >
> > > http://cr.openjdk.java.net/~mbaesken/webrevs/8218136.1/
> > >
> > > - adjusted  globalDefinitions_xlc.hpp
> >
> > I don't think it makes sense to keep the comment which was obviously
> > copied from the gcc file:
> >
> >   // On Linux NULL is defined as a special type '__null'. Assigning
> > __null to
> >    // integer variable will cause gcc warning. Use NULL_WORD in places
> > where a
> >    // pointer is stored as integer value.  On some platforms,
> > sizeof(intptr_t) >
> >    // sizeof(void*), so here we want something which is integer type,
> > but has the
> >    // same size as a pointer.
> >
> > Rather something like:
> >
> > // Some platform/tool-chain combinations can't assign NULL to an integer
> > // type so we define NULL_WORD to use in those contexts. For xlc they
> > // are the same.
> >
> > Thanks,
> > David
> >
> >