Integrated: 8282045: When loop strip mining fails, safepoints are removed from loop anyway

[Roland Westrelin]

On Thu, 17 Feb 2022 10:00:32 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> I noticed that if loop strip mining fails because a safepoint is not
> found right above the exit test (following partial peel for instance),
> all safepoints are removed from the loop anyway. That's fixed by the
> change in IdealLoopTree::counted_loop() where rather than test if loop
> strip mining is enabled, the check now verifies that loop strip mining
> was successful.
> 
> With that change,
> compiler/c2/irTests/TestAutoVectorization2DArray.java fails. The loop
> is not converted into a strip mined loop because there's no safepoint
> above the exit test after partial peeling. The loop strip mining logic
> is too strict when it comes to the safepoint location. Any safepoint
> that dominates the exit and is in the loop as long as there's no side
> effect between the safepoint and the exit can be used. The patch
> implements that change as well. TestAutoVectorization2DArray.java
> passes as a result.
> 
> The existing requirement to have no safepoint on the backedge is too
> strict as well. If the loop has another safepoint that can be used for
> strip mining, then the safepoint on the backedge can safely be
> dropped. That's also implemented by the patch.

This pull request has now been integrated.

Changeset: 2c5d266f
Author:    Roland Westrelin <roland at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/2c5d266f9f20005bc2a6c30dcaa95b059ea59d74
Stats:     203 lines in 3 files changed: 165 ins; 25 del; 13 mod

8282045: When loop strip mining fails, safepoints are removed from loop anyway

Reviewed-by: thartmann, chagedorn

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PR: https://git.openjdk.java.net/jdk/pull/7513