RFR: 8274855: vectorapi tests failing with assert(!vbox->is_Phi()) failed [v2]

[Igor Veresov]

> We need to handle the case when the allocation input to `VectorBoxNode` is a phi but the vector input is not, which can definitely be the case if the vector input has been value-numbered. It seems to be safe to do by construction because `VectorBoxNode` and `VectorBoxAllocation` come in a specific order as a result of expanding an intrinsic call. After that, if any of the inputs to VectorBoxNode are value-numbered they can only move up and are guaranteed to dominate.

Igor Veresov has updated the pull request incrementally with two additional commits since the last revision:

 - Fix spelling.
 - Add comments.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6162/files
  - new: https://git.openjdk.java.net/jdk/pull/6162/files/1889bc60..fd4fbe19

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6162&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6162&range=00-01

  Stats: 7 lines in 1 file changed: 7 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6162.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6162/head:pull/6162

PR: https://git.openjdk.java.net/jdk/pull/6162