RFR: 8252583: Make PhiNode::is_copy() debug only

Mon Sep 21 06:35:57 UTC 2020

On Mon, 21 Sep 2020 06:27:41 GMT, Roberto Castañeda Lozano <github.com+8792647+robcasloz at openjdk.org> wrote:

> Convert `PhiNode::is_copy()` into an actual, debug-only predicate. Replace calls to `is_copy()` from non-debug code
> with explicit assertions. Remove dead loop in debug-only `MergeMemStream::match_memory()`.

Convert PhiNode::is_copy() into an actual, debug-only predicate. Replace calls
to is_copy() from non-debug code with explicit assertions. Remove dead loop in
debug-only MergeMemStream::match_memory().

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PR: https://git.openjdk.java.net/jdk/pull/275