RFR(S): 8203425: assert(is_Loop()) failed: invalid node class

Nils Eliasson nils.eliasson at oracle.com
Wed May 30 12:43:58 UTC 2018

Bumping this.

// N

On 2018-05-23 14:14, Nils Eliasson wrote:
> Hi,
> This is a follow up to JDK-8203215 that caused failures in testing.
> JDK-8203215 added a call to igvn.optimize after beautify_loops to 
> handle phi-nodes that have lost their loop edge and now produce loop 
> invariant data. In testing a failure came up - the igvn.optimize call 
> can sometimes eliminate a loop node when the phis are all invariant.
> When fixing this I observed that a loop might be removed, and that 
> another region that is a subset of the first is selected as new loop, 
> and then there might be new loop invariant phis (not observed).
> This change introduces a fix point iteration for beautify_loops, until 
> no more loop structure changes has been made. This might sound 
> expensive but In practice beautify-loops is called one additional time 
> at first insertion of loop-nodes. I have seen one case of cascading 
> loop reductions when beautify_loops is called three times. The upside 
> is that we reach fix point for PhaseIdealLoop faster since these 
> changes would guarantee to trigger a major change in next iteration 
> instead.
> https://bugs.openjdk.java.net/browse/JDK-8203425
> http://cr.openjdk.java.net/~neliasso/8203425/webrev.01/
> Regards,
> Nils Eliasson

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