RFR: 8255553: [PPC64] Introduce and use setbc and setnbc P10 instructions [v8]

[Ziviani]

> - setbc RT,BI: sets RT to 1 if CR(BI) is 1, otherwise 0.
> - setnbc RT,BI: sets RT to -1 if CR(BI) is 1, otherwise 0.
> Ref: PowerISA 3.1, page 129.
> 
> These instructions are particularly interesting to improve the following
> pattern `(src1<src2)? -1: ((src1>src2)? 1: 0)`, which can be found in
> `instruct cmpL3_reg_reg_ExEx()@ppc.ad`, by removing its branches.
> 
> Long.toString, that generate such pattern in getChars, has showed a
> good performance gain by using these new instructions.
> 
> Example:
> for (int i = 0; i < 200_000; i++)
>   res = Long.toString((long)i);
> 
> java -Xcomp -XX:CompileThreshold=1 -XX:-TieredCompilation TestToString
> 
> Without setbc (average): 0.1178 seconds
> With setbc (average): 0.0396 seconds

Ziviani has updated the pull request incrementally with one additional commit since the last revision:

  Implementing code review suggestions
  
  Signed-off-by: Jose Ricardo Ziviani <joserz at linux.ibm.com>

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/907/files
  - new: https://git.openjdk.java.net/jdk/pull/907/files/68081ca6..ff1ecd91

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=907&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=907&range=06-07

  Stats: 14 lines in 4 files changed: 2 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/907.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/907/head:pull/907

PR: https://git.openjdk.java.net/jdk/pull/907