RFR: 8361702: C2: assert(is_dominator(compute_early_ctrl(limit, limit_ctrl), pre_end)) failed: node pinned on loop exit test? [v3]

[Christian Hagedorn]

On Fri, 25 Jul 2025 14:58:47 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> A node in a pre loop only has uses out of the loop dominated by the
>> loop exit. `PhaseIdealLoop::try_sink_out_of_loop()` sets its control
>> to the loop exit projection. A range check in the main loop has this
>> node as input (through a chain of some other nodes). Range check
>> elimination needs to update the exit condition of the pre loop with an
>> expression that depends on the node pinned on its exit: that's
>> impossible and the assert fires. This is a variant of 8314024 (this
>> one was for a node with uses out of the pre loop on multiple paths). I
>> propose the same fix: leave the node with control in the pre loop in
>> this case.
>
> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update src/hotspot/share/opto/loopopts.cpp
>   
>   Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>

Marked as reviewed by chagedorn (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/26424#pullrequestreview-3060627024