RFR: 8344104: TestMergeStores fails with ArrayIndexOutOfBoundException [v2]

[Emanuel Peter]

> Test-bug: `RANDOM.nextInt()` would occasionally return a `min_int`. And sadly this overflows: `Math.abs(min_int) == min_int`. Wen we calculate it `% 100`, it still gives us a negative value, and we end up out of bounds. Fixed with a mask.

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

  do what shipilev said

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22080/files
  - new: https://git.openjdk.org/jdk/pull/22080/files/3e95dfbc..ebce52c7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22080&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22080&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/22080.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22080/head:pull/22080

PR: https://git.openjdk.org/jdk/pull/22080