[14] RFR(S): 8229994: assert(false) failed: Bad graph detected in get_early_ctrl_for_expensive

[Vladimir Ivanov]

Looks good.

Best regards,
Vladimir Ivanov

On 05.12.2019 16:22, Christian Hagedorn wrote:
> Hi
> 
> Please review the following patch:
> https://bugs.openjdk.java.net/browse/JDK-8229994
> http://cr.openjdk.java.net/~chagedorn/8229994/webrev.00/
> 
> As a part of loop peeling, loop-invariant dominating tests are moved out 
> of the loop [1]. Doing so requires to change all control inputs coming 
> from an independent test 'test' to data nodes inside the loop body to 
> use the peeled version 'peeled_test' of 'test' instead [2]: the control 
> test->data will be changed to peeled_test->data. If a data node is 
> expensive then an assertion [3] checks the dominance relation of 'test' 
> and 'peeled_test' ('peeled_test' should dominate 'test') but fails to 
> find 'peeled_test' as part of the idom chain starting from the previous 
> control input 'test' of that expensive node.
> 
> The reason is that the idom information was not correctly set before at 
> [4] after creating the peeled nodes. If 'head' (a CountedLoop node) has 
> another OuterStripMinedLoop node, let's say 'outer_head', as an input 
> then 'outer_head' is set as idom of 'head' instead of setting the idom 
> of 'outer_head' to the new loop entry from the peeled iteration. We then 
> miss all the idom information of the peeled iteration and the idom of 
> 'outer_head' still points to the old loop entry node before peeling.
> 
> The fix is straight forward to also account for loop strip mined loops 
> when correcting the idom to the new loop entry from the peeled iteration 
> at [4].
> 
> Thank you!
> 
> Best regards,
> Christian
> 
> 
> [1] 
> http://hg.openjdk.java.net/jdk/jdk/file/99b71c5b02ff/src/hotspot/share/opto/loopTransform.cpp#l669 
> 
> [2] 
> http://hg.openjdk.java.net/jdk/jdk/file/99b71c5b02ff/src/hotspot/share/opto/loopopts.cpp#l271 
> 
> [3] 
> http://hg.openjdk.java.net/jdk/jdk/file/99b71c5b02ff/src/hotspot/share/opto/loopnode.cpp#l153 
> 
> [4] 
> http://hg.openjdk.java.net/jdk/jdk/file/99b71c5b02ff/src/hotspot/share/opto/loopTransform.cpp#l658 
>