RFR: 8292301: [REDO v2] C2 crash when allocating array of size too large [v4]

[Xin Liu]

On Fri, 9 Sep 2022 12:33:15 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> On top of the redo, this fixed 2 bugs:
>> 
>> 8288184: the problem here is that the ValidLengthTest input of an
>> AllocateArrayNode becomes a constant. The CatchNode would then change
>> types if it was reprocessed but it's not. Custom logic is needed to
>> enqueue the CatchNode when the ValidLengthTest input of an
>> AllocateArrayNode changes. The CastII out of the AllocateArrayNode
>> becomes top but the fallthrough path doesn't die. This happens with
>> igvn in the case of the bug but could also happen with ccp. I fixed
>> both in this patch.
>> 
>> 8291665: the code pattern for this is 2 AllocateArrayNodes out of loop
>> with a shared ValidLengthTest input in a loop. When the loop is cloned
>> that causes Phis to be added between the AllocateArrayNodes and the
>> BoolNode of the ValidLengthTest inputs. Split if runs next and it
>> doesn't expect the Phi at the ValidLengthTest inputs. The fix here is
>> to clone the Bool/Cmp subgraph down on loop cloning. There's logic for
>> that when the use of the bool is an If for instance so I simply added
>> a special case to run that logic for an AllocateArrayNode use as
>> well. Note that the test case I added fails reliably on 11 but not
>> with the current jdk developement branch. AFAICT, the bug is there but
>> something unrelated changed and a slightly different graph is built
>> for the test case that prevents split if.
>
> Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 12 commits:
> 
>  - comments
>  - Merge branch 'master' into JDK-8292301
>  - Update src/hotspot/share/opto/phaseX.cpp
>    
>    Co-authored-by: Tobias Hartmann <tobias.hartmann at oracle.com>
>  - undo needless change
>  - dos->unix test file
>  - move tests
>  - test fix
>  - fix
>  - test
>  - test for 8288184
>  - ... and 2 more: https://git.openjdk.org/jdk/compare/8e22f2bb...9d92011a

LGTM.

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

Marked as reviewed by xliu (Committer).

PR: https://git.openjdk.org/jdk/pull/10038