JDK10/RFR(L): 8144448: Avoid placing CTI immediately following or preceding RDPC instruction.

[Vladimir Kozlov]

Patric,

assembler_sparc.cpp - may be use BytesPerInstWord instead of 4.

In sparc.ad in MachConstantBaseNode::emit() can you use nop() in case 
disp == 0? To avoid changing O7 reg.

Thanks,
Vladimir

On 6/15/17 9:06 AM, Patric Hedlin wrote:
> Dear all,
> 
> I would like to ask for help to review the following change/update:
> 
> Issue:    https://bugs.openjdk.java.net/browse/JDK-8144448
> 
> Webrev:   http://cr.openjdk.java.net/~neliasso/phedlin/tr8144448/
> 
> Prerequisite: https://bugs.openjdk.java.net/browse/JDK-8181853
> 
> 
> *** As a comment to the discussion on how to simplify processing of 
> "mundane" changes,
>      this change/update comes with an additional prerequisite (patch) 
> cleaning-up
>      whitespace and two lingering uses of 'NOT_LP64' and 'LP64_ONLY'.
> 
> Prerequisite: http://cr.openjdk.java.net/~neliasso/phedlin/tr8144448.pre/
> 
> 
> 8144448: Avoid placing CTI immediately following or preceding RDPC 
> instruction.
> 
>      Approach taken here is to handle 'rdpc' in the same manner as 
> 'cbcond', using
>      a simple scheme to prohibit the assembler from emitting any 'rdpc' 
> instruction
>      back-to-back with other CTI ('rdpc' itself included), inserting 
> 'nop' as needed.
> 
> 
> Caveat:
> 
>      This change is applied to all generations of SPARC cores event 
> though it is the
>      SPARC Core S5 that is the actual target. Benchmarking on T4 and M7 
> suggests that
>      there is no penalty. This choice (which is subject to change) has 
> been made in
>      order to give the update some mileage while waiting for Core S5 
> hardware to be
>      available in regular testing.
> 
> 
> Testing:
> 
>      Mostly tested on JDK9 (jtreg/RBT/hotspot/tier0-comp).
>      Testing on JDK10 (jtreg/RBT/hotspot/precheckin-comp).
> 
> 
> Best regards,
> Patric