RFR: 6232281: -XX:-UseLoopSafepoints causes assert(v_false, "Parse::remove_useless_nodes missed this node")

[Roberto Castañeda Lozano]

On Thu, 19 Nov 2020 09:07:30 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> Check for nodes missed by `remove_useless_nodes()` only if PhaseRemoveUseless has actually been run. This makes it possible to use `-XX:-UseLoopSafepoints` without crashing trivially, although implicit assumptions in other parts of C2 about the existence of loop safepoints might lead to more subtle failures for more complex methods.
>
> Check for nodes missed by remove_useless_nodes() only if PhaseRemoveUseless has
> actually been run. This makes it possible to use -XX:-UseLoopSafepoints without
> crashing trivially, although implicit assumptions in other parts of C2 about the
> existence of loop safepoints might lead to more subtle failures for more complex
> methods.

Tested on hs-tier{1,2,3}.

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PR: https://git.openjdk.java.net/jdk/pull/1311