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

[Tobias Hartmann]

Hi Christian,

looks good to me but the CompileCommand argument in the @run statement of the test should come
before the test class name (no new webrev required).

Best regards,
Tobias

On 05.12.19 14:22, 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