RFR: 8333099: Missing check for is_LoadVector in StoreNode::Identity [v3]

[Damon Fenacci]

> [JDK-8325520](https://bugs.openjdk.org/browse/JDK-8325520) introduced a check for type equality in `StoreNode::Identity` in the specific case of a load vector followed by a store vector.
> Unfortunately the memory node operand might actually not be of type `LoadVector`. So, before retrieving its type, a check for `is_LoadVector` is necessary.

Damon Fenacci has updated the pull request incrementally with one additional commit since the last revision:

  JDK-8333099: fix indentation

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19449/files
  - new: https://git.openjdk.org/jdk/pull/19449/files/f4150d37..fd7aaac6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19449&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19449&range=01-02

  Stats: 27 lines in 1 file changed: 0 ins; 0 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/19449.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19449/head:pull/19449

PR: https://git.openjdk.org/jdk/pull/19449