RFR: 8308975: Fix signed integer overflow in compiler code, part 2 [v3]

[Dean Long]

> This is a followup from part 1.  I had to use java_add/subtract/multiply/negate in a few more places.
> cpu_loads_process had an overflow on BSD when the first snapshot is relative to the epoch in 1970.
> Use unsigned for C2 Type hash functions.

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

  fix potential -Werror=conversion issue

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14188/files
  - new: https://git.openjdk.org/jdk/pull/14188/files/a50b4f01..0f71db99

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14188&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14188&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14188.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14188/head:pull/14188

PR: https://git.openjdk.org/jdk/pull/14188