8367244: [lworld] C2 compilation fails with assert "no node with a side effect"

[mhaessig]

Problem Analysis

The stress test compiler/valhalla/inlinetypes/TestAcmpWithUnstableIf.java, which uses the StressUnstableIfTrap flag, failed intermittently with the assert "no node with a side effect" during C2 compilation. I tracked down the origin of the failure to the raw store of the unstable if trap stress counter that was missing a memory edge to the backedge phi and thus had no side effect in the loop, which lead to the aforementioned assert. During parsing, the missing memory edge gets discarded with as vestigial parsing state when do_if() ends up stopped(). However, the effect of the stress counter should still be wired back into the backedge since it will be incremented in the next iteration.

Patch Description

To prevent the stress counters memory state being lost to PreserveJVMState, I pass it to the caller over an out-parameter and set_memory with that node, similar to what is already done for control. This is only necessary for the two last invocation of do_if() in do_acmp() where they are actually allowed to trap. Further, this PR reenables StressUnstableIfTrap in compiler/valhalla/inlinetypes/TestAcmpWithUnstableIf.java.

Testing

• tier1,tier2,tier3 plus internal stress testing

---

Progress

• Change must not contain extraneous whitespace

Issue

• JDK-8367244: [lworld] C2 compilation fails with assert "no node with a side effect" (Bug - P4)

Reviewing

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8367244: [lworld] C2 compilation fails with assert "no node with a side effect"

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At the time when this comment was updated there had been 2 new commits pushed to the lworld branch:

• 7b5f105: 8370484: [lworld] PhaseOutput::FillLocArray asserts with Unexpected type: anyptr
• 88f413d: [lworld] Don't run TestMethodHandles.java with -Xcomp

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