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

[Kim Barrett]

On Fri, 25 Dec 2020 10:32:09 GMT, Hao Sun <github.com+16932759+shqking at openjdk.org> wrote:

>> 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

Marked as reviewed by kbarrett (Reviewer).

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

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