NPE dumping CFG

[chrisseaton]

% ./truffleruby-21.2.0.1-macos-amd64/bin/ruby --experimental-options --vm.Dgraal.Dump=:3 --engine.TraceCompilation --engine.CompileOnly=foo --vm.Dgraal.PrintBackendCFG=true test.rb
...
[engine] opt done     Object#foo                                                  |AST   18|Tier 1|Time  308(  59+249 )ms|Inlined   0Y   0N|IR   105/  206|CodeSize    754|Addr 0x1195d8000|Src test.rb:1
Dumping IGV graphs in /Users/chrisseaton/Documents/ruby-compiler-explorer/graal_dumps/2021.09.20.00.22.40.922
CFGPrinter: Exception during output of After code generation: java.lang.NullPointerException
java.lang.NullPointerException
        at org.graalvm.compiler.code.HexCodeFileDisassemblerProvider.disassemble(HexCodeFileDisassemblerProvider.java:71)
        at org.graalvm.compiler.code.HexCodeFileDisassemblerProvider.disassembleCompiledCode(HexCodeFileDisassemblerProvider.java:56)
        at org.graalvm.compiler.printer.CFGPrinterObserver.disassemble(CFGPrinterObserver.java:301)
        at org.graalvm.compiler.printer.CFGPrinterObserver.dumpSandboxed(CFGPrinterObserver.java:238)
        at org.graalvm.compiler.printer.CFGPrinterObserver.dumpSandboxed(CFGPrinterObserver.java:161)
        at org.graalvm.compiler.printer.CFGPrinterObserver.dump(CFGPrinterObserver.java:86)

@eregon

[munishchouhan]

@chrisseaton thanks for reporting the issue

[munishchouhan]

@eregon please check and advise

[eregon]

It looks very much like a compiler issue, reassigning to Doug.

[dougxc]

Hi @chrisseaton is there any chance you could try reproduce this on a 21.3 snapshot? There have been some changes in that area so it would be interesting to know if the problem still exists.
Also, looking at the code I don't think this exception should actually cause a compilation to fail. Is that the case for you?

[chrisseaton]

I don't think it causes compilation failure - it just means I don't get the graphs I want.

I will check on the snapshot today.

[dougxc]

Ok, thanks.

Of course, any help you can provide in terms of debugging the cause would be greatly appreciated.