RFR: 8253756: C2 CompilerThread0 crash in Node::add_req(Node*) [v2]

[Tobias Hartmann]

On Wed, 7 Oct 2020 15:20:26 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> The outer strip mined loop is initially created as a skeleton and then
>> expanded once loop opts are over. As long as it is a skeleton, the
>> OuterStripMinedLoopEndNode cannot be constant folded because its input
>> is a place holder. So OuterStripMinedLoopEndNode::Value() blocks
>> constant folding. This bug triggers because the
>> OuterStripMinedLoopEndNode input after expansion is a constant but the
>> OuterStripMinedLoopEndNode is not constant folded (i.e. it's a dead
>> loop but it stays in the graph). The fix I propose is to change the
>> behavior OuterStripMinedLoopEndNode::Value() so it blocks constant
>> folding only until expansion but not after.
>
> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove debugging code

Looks reasonable to me.

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/537