Flaky hit of `function.is_background_optimizable() || !Compiler::IsBackgroundCompilation()` with --enable-isolate-groups

[mkustermann]

From this log:

/===============================================================================================\
| dartk-strong-linux-debug-x64:lib/isolate/raw_port_test/0 broke (Pass -> Crash, expected Pass) |
\===============================================================================================/

--- Command "vm" (took 04.000738s):
DART_CONFIGURATION=DebugX64 out/DebugX64/dart --enable-isolate-groups --experimental-enable-isolate-groups-jit --sound-null-safety --ignore-unrecognized-flags --packages=/b/s/w/ir/.packages /b/s/w/ir/tests/lib/isolate/raw_port_test.dart

exit code:
-6

stdout:
unittest-suite-wait-for-done

stderr:
../../runtime/vm/compiler/jit/compiler.cc: 704: error: expected: function.is_background_optimizable() || !Compiler::IsBackgroundCompilation()
version=2.12.0-edge.97e2f3ddc5fc5c30809f0447d180045e6878139e (be) (Mon Feb 1 18:26:29 2021 +0000) on "linux_x64"
pid=16338, thread=16346, isolate_group=main(0x55c0bc689c00), isolate=remote2(0x55c0bc98c800)
isolate_instructions=55c0b9d9b260, vm_instructions=55c0b9d9b260
  pc 0x000055c0ba165d8c fp 0x00007f51dd0fd860 dart::Profiler::DumpStackTrace(void*)+0x7c
  pc 0x000055c0b9d9b412 fp 0x00007f51dd0fd940 dart::Assert::Fail(char const*, ...)+0x82
  pc 0x000055c0ba2443d5 fp 0x00007f51dd0fdb50 out/DebugX64/dart+0x1ff63d5
  pc 0x000055c0ba244a41 fp 0x00007f51dd0fdbe0 dart::Compiler::CompileOptimizedFunction(dart::Thread*, dart::Function const&, long)+0x121
  pc 0x000055c0ba245750 fp 0x00007f51dd0fdc90 dart::BackgroundCompiler::Run()+0x1d0
  pc 0x000055c0ba22590b fp 0x00007f51dd0fdd30 dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*)+0x1cb
  pc 0x000055c0ba226349 fp 0x00007f51dd0fdd80 dart::ThreadPool::Worker::Main(unsigned long)+0x179
  pc 0x000055c0ba15e859 fp 0x00007f51dd0fded0 out/DebugX64/dart+0x1f10859
-- End of DumpStackTrace

--- Re-run this test:
python tools/test.py -n dartk-strong-linux-debug-x64 lib/isolate/raw_port_test/0

/cc @aam Maybe there are still some BG compiler bailouts that need to be removed?

[aam]

Looks like this crash is from over a month ago, seems like its no longer happening.

[mkustermann]

The issue is still there, it's just very unlikely to be hit. I've a cl/187901 out for fixing it.