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List:       openjdk-hotspot-compiler-dev
Subject:    Integrated: 8290781: Segfault at PhaseIdealLoop::clone_loop_handle_data_uses
From:       Roland Westrelin <roland () openjdk ! org>
Date:       2022-08-31 9:26:20
Message-ID: yqop2Yoi3puGKa5BEHyuMoX79n-tNRfchQj86nSrDxo=.a1914f26-06d6-46bf-ac6f-7db6ed1fc33e () github ! com
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On Wed, 24 Aug 2022 07:58:11 GMT, Roland Westrelin <roland@openjdk.org> wrote:

> In the test case, both:
> 
>             v1 = array[i];
> (in the first loop), and
> 
>             v += array[i-1];
> 
> (in the second one) access the same element. The bound check for the
> second access is optimized out and the load of that access becomes
> control dependent on the range check of the first one.
> 
> In the context of loop strip mining, data nodes that are in the outer
> loop are expected to be reachable from the safepoint node. There are
> rare case when it's not the case so I added logic to fix those cases
> before loop cloning. That logic covers both nodes that have control in
> the outer loop and control input in the outer loop. That logic is
> incorrect (in the case of a node with a control input in the outer
> loop): when cloning the first loop body, that logic finds the load
> referenced from the range check in the loop body. That load has a
> control input that's in the inner loop. But the logic only check
> whether it's in the outer loop: anything in the inner loop is also in
> the outer loop with that logic. The control of the load is then
> wrongly updated to be outside the outer loop. That then causes a crash
> because the load is recorded as being in the body of the second loop
> but its control is not.
> 
> The fix I propose stengthen the logic that checks for nodes in the
> outer loop: it checks that the control input is in the outer loop but
> not in the inner loop.

This pull request has now been integrated.

Changeset: 4c90e87a
Author:    Roland Westrelin <roland@openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/4c90e87a6fa83a66fdb8767b999879600629f1f6
Stats:     82 lines in 2 files changed: 78 ins; 3 del; 1 mod

8290781: Segfault at PhaseIdealLoop::clone_loop_handle_data_uses

Reviewed-by: chagedorn, thartmann

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

PR: https://git.openjdk.org/jdk/pull/9997
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