RFR(S): 8186611: s390: Add missing compiler barriers and fix assembler

[Lindenmaier, Goetz]

Hi Martin,

thanks for these hard-to-spot fixes! Reviewed.

Best regards,
  Goetz.

> -----Original Message-----
> From: Doerr, Martin
> Sent: Dienstag, 22. August 2017 21:04
> To: hotspot-runtime-dev at openjdk.java.net; Lindenmaier, Goetz
> <goetz.lindenmaier at sap.com>
> Cc: Kim Barrett <kim.barrett at oracle.com>
> Subject: RFR(S): 8186611: s390: Add missing compiler barriers and fix
> assembler
> 
> Hi,
> 
> 
> 
> please review my small s390 fix.
> 
> As discovered by Kim Barret, the current inline assembly implementation of the
> atomics lacks "memory" in the clobber lists. This may lead to undesired
> compiler optimizations. We have never observed an issue, but it should be
> fixed.
> 
> Another bug is in the assembler encoding of the mvh* instructions which take
> and Address parameter.
> 
> In addition, I've improved an assertion which prevents the compiler from
> generating multiple accesses.
> 
> 
> 
> Webrev:
> 
> http://cr.openjdk.java.net/~mdoerr/8186611_s390_fixes/webrev.00/
> 
> 
> 
> Thanks and best regards,
> 
> Martin
> 
>