RFR: 8258382: Fix optimization-unstable code involving pointer overflow [v2]

[Hao Sun]

> Optimization-unstable code refers to code that is unexpectedly discarded
> by compiler optimizations due to undefined behavior in the program.
> 
> We applied a static checker called STACK (prototype from SOSP'13 paper
> [1]) to OpenJDK source code and found the following two sites of
> potential unstable code involving pointer overflow.
> 
> Removing undefined behaviors would make the code stable.
> 
> [1] https://css.csail.mit.edu/stack/
> 
> --------
> Note that we tested locally Jtreg tests ( tier1 and jdk::tier3) were passed on Linux x86/aarch64 machines after apply this patch.

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

  Fix unstable code involving pointer overflow only
  
  Move the patch involving singed integer overflow into another PR.
  In this patch we only fix optimization-unstable code involving pointer
  overflow.
  
  Update the patch based on feedback from upstream.
  1) Remove unnecessary comment.
  2) Remove unnecessary check between end() and top()
  3) Use pointer_delta() to compute the offset between two addresses.
  
  Change-Id: Icade8e1a4b684081036c85fd2a2b65b5c3b27f54
  CustomizedGitHooks: yes

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1886/files
  - new: https://git.openjdk.java.net/jdk/pull/1886/files/ca1fbaee..4fc79491

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1886&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1886&range=00-01

  Stats: 12 lines in 5 files changed: 0 ins; 2 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1886.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1886/head:pull/1886

PR: https://git.openjdk.java.net/jdk/pull/1886