RFR: 8258946: Fix optimization-unstable code involving signed integer overflow

[Tobias Hartmann]

On Mon, 28 Dec 2020 10:34:30 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 six sites of
> potential unstable code involving signed integer 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.

Looks good to me.

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1900