See http://www.scala-lang.org/blog/2016/07/08/trait-method-performance.html#back-to-default-methods for the motivating example. This bug follows up why non-CHA inlining produces suboptimal loop.

While the same can be demonstrated with default methods that do not enjoy CHA inlining due to JDK-8036580, we can also show the same on virtual methods with -XX:-UseCHA. While we can argue that CHA *should* be faster because it uses static information for inlining, it is very weird to see the impact on loop optimizer.

Running this test:

    interface I {
        int getV();
    }

    abstract class A implements I {
        public int accessVirtual() { return getV(); }
    }

    class C extends A {
        public int v = 0;
        public int getV() { return v; }
    }

    final int NB = 1000;

    public C c;

    @Setup
    public void setup() {
        c = new C();
    }

    @Benchmark
    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
    public int test() {
        int value = 0;
        for (int i = 0; i < NB; i++) {
            c.v = i;
            value += c.accessVirtual();
        }
        return value;
    }

(full test: http://cr.openjdk.java.net/~shade/8161334/CHAnoCHA.java, http://cr.openjdk.java.net/~shade/8161334/benchmarks.jar)

...will yield different performance with -XX:+UseCHA and -XX:-UseCHA. The performance difference seems to be explained with the suboptimal loop generation in non-CHA case, and at least here reaches 20%.

Disassemblies:
 http://cr.openjdk.java.net/~shade/8161334/cha.perfasm
 http://cr.openjdk.java.net/~shade/8161334/no-cha.perfasm

It seems to start with a subtly different IRs generated for CHA and non-CHA inlining:
 http://cr.openjdk.java.net/~shade/8161334/cha-after-parsing.png
 http://cr.openjdk.java.net/~shade/8161334/no-cha-after-parsing.png