[jdk11u-dev] RFR: 8272131: PhaseMacroExpand::generate_slow_arraycopy crash when clone null CallProjections.fallthrough_ioproj

[Hui Shi]

Please help review this backport for 8272131: C2 crash in PhaseMacroExpand::generate_slow_arraycopy because arraycopy node's _ioproj_fallthrough is NULL.

Conflicts when backport
In jdk18:  field name is fallthrough_ioproj , and it is in PhaseMacroExpand's CallProjections class.
In jdk11:  field name is _ioproj_fallthrough, and it is directly in PhaseMacroExpand class.

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Commit messages:
 - Backport 5350b9901c6cebe5d40bbba9a31d1f26285b1cd6

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/247/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=247&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272131
  Stats: 75 lines in 2 files changed: 72 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/247.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/247/head:pull/247

PR: https://git.openjdk.java.net/jdk11u-dev/pull/247