JVM-2571: BlackholeSyncEATest is broken after PEA is enabled

[navyxliu]

This patch fixed regression test 'BlackholeSyncTest' on all platforms. It explicitly disables PEA in the testcase because it contradicts the assumption.

PEA postpones the object allocation to its escaping. If the transformation surpass a synchronized(o) {} construct, it's possible to elide the lock. We explicitly disable PEA in the testcase so it only tests C2 Escape Analysis.

[caojoshua]

I'm surprised EA cannot ellide the lock in the blackhole case. I guess control flow analysis through PEA helps

[navyxliu]

@caojoshua We did. The test expects to capture FastLock/FastUnlock nodes but PEA manage to elide them. that's why the test failed.

Aleksei says that the semantic of 'blackhole(x)' to make o 'GlobalEscaped'.
PEA take actions even before parser encounter Blackhole node. in current design, it's hard to respect the semantic of blackhole.

    @Test
    @IR(counts = {IRNode.FAST_LOCK, "1"})
    @IR(counts = {IRNode.FAST_UNLOCK, "1"})
    static void testBlackholed() {
        Object o = new Object();
        synchronized (o) {} // elided by PEA
        blackhole(o);
    }

[navyxliu]

Let's ignore blackhole node for time being. we will revisit this issue with a new design.