IGV scheduling crashes when breaking critical edges that target Region nodes not marked with the 'is_block_start' property (such as node 137 in the attached image, where 108 -> 137 is a critical edge). In this case, ServerCompilerScheduler.buildBlocks() fails to create a dedicated block for breaking the critical edge, which leads to ServerCompilerScheduler.scheduleBlock() failing to schedule the ill-formed Region nodes and, finally, to an assertion failure.

HOW TO REPRODUCE

Unzip and open failure.zip (attached) in IGV. The following failure is printed to .igv.log:

[INFO] java.lang.AssertionError
[INFO] at com.sun.hotspot.igv.servercompiler.ServerCompilerScheduler.scheduleBlock(ServerCompilerScheduler.java:448)
[INFO] at com.sun.hotspot.igv.servercompiler.ServerCompilerScheduler.scheduleLocal(ServerCompilerScheduler.java:389)
[INFO] at com.sun.hotspot.igv.servercompiler.ServerCompilerScheduler.schedule(ServerCompilerScheduler.java:350)