Repeating deoptimizations when compiling Scala

[vjovanov]

When compiling scala programs there are repeating deoptimizations that seem suspicious. To easily reproduce:

git clone https://github.com/scala/compiler-benchmark.git
cd compiler-benchmark
git reset --hard 367811e9a2fe070ae34d10a7986a8a5d444b38a2
sbt
sbt> hot -psource=scalap -wi 100 -i 5 -f1 -jvm <graalvm>/Contents/Home/bin/java -jvmArgs -XX:+PrintCompilation

Observe the logs and see a few dozen methods that get compiled on every iteration of the benchmark. An example is scala.reflect.internal.tpe.TypeComparers$class::firstTry$1.

[alina-yur]

@vjovanov @mur47x111 I assume this can be closed now?

[mur47x111]

We have attached speculation to prevent most of the repeated deoptimization and I think this can be closed.