RFR: 8312077: Fix signed integer overflow, final part [v6]

[Dean Long]

> This is hopefully the last set of integer overflow fixes for hotspot.  Some of the counters I changed to unsigned are updated in platform-specific code, so I could use some help testing on arm, ppc,  riscv, and s390.

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

  add comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14883/files
  - new: https://git.openjdk.org/jdk/pull/14883/files/7ed08326..0c14f96c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14883&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14883&range=04-05

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14883.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14883/head:pull/14883

PR: https://git.openjdk.org/jdk/pull/14883