RFR: 8267904: C2 crash when compile negative Arrays.copyOf length after loop [v2]

[Hui Shi]

On Mon, 31 May 2021 07:33:36 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> Hui Shi has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.
>
> src/hotspot/share/opto/library_call.cpp line 4474:
> 
>> 4472:           assert(prev->type()->is_int()->_lo == cur->type()->is_int()->_lo, "not same");
>> 4473:           assert(prev->type()->is_int()->_hi == cur->type()->is_int()->_hi, "not same");
>> 4474:         }
> 
> Is this really necessary? Have you seen cases with multiple identical CastII nodes? Or is it to be extra cautious?

Thanks for your comment!

Multiple identical CastII node do happens and check is added to ensure they are identical CastIINodes. Cases are:
1. CastIINode created in GraphKit::new_array 
2. CastIINode might created before inline_arraycopy if GraphKit::load_array_length is invoked. If new array's length is loaded multiple times before System.arraycopy, there could be multiple CastIINode.

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PR: https://git.openjdk.java.net/jdk/pull/4238