Integrated: 8356865: C2: Unreasonable values for debug flag FastAllocateSizeLimit can lead to left-shift-overflow, which is UB

[Benoît Maillard]

On Mon, 16 Jun 2025 14:50:46 GMT, Benoît Maillard <bmaillard at openjdk.org> wrote:

> This PR adds a range constraint for the `-XX:FastAllocateSizeLimit` debug flag. This prevents undefined behavior caused by left-shift overflow of the flag value in `GraphKit::new_array`.
> 
> ### Testing
> - [x] [GitHub Actions](https://github.com/benoitmaillard/jdk/actions?query=branch%3AJDK-8356865)
> - [x] tier1-3, plus some internal testing
> - [x] Manual testing with values known to previously cause undefined behavior
> 
> Thanks!

This pull request has now been integrated.

Changeset: c220b135
Author:    Benoît Maillard <bmaillard at openjdk.org>
Committer: Emanuel Peter <epeter at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/c220b1358c91bce2eb7515e9f600004c7b975ee6
Stats:     64 lines in 3 files changed: 64 ins; 0 del; 0 mod

8356865: C2: Unreasonable values for debug flag FastAllocateSizeLimit can lead to left-shift-overflow, which is UB

Reviewed-by: epeter, mhaessig

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

PR: https://git.openjdk.org/jdk/pull/25834