RFR: 8332905: C2 SuperWord: bad AD file, with RotateRightV and first operand not a pack

[Emanuel Peter]

I just discovered this bug by manual code inspection, and found a reproducer.

It seems to be a regression of [JDK-8248830](https://bugs.openjdk.org/browse/JDK-8248830), that is when RotateRightV was added to SuperWord.

The problem is that we directly get the input node, rather than the `vector_opd`, which fails if that input is not a vector already, but for example a `PopulateIndex` pattern that is only vectorized when calling `vector_opd`.

Before this patch: it looks like this:

      } else if (VectorNode::is_scalar_rotate(n)) {
        Node* in1 = first->in(1);
        Node* in2 = first->in(2);


But at least `in1` should be using `vector_opd`, like most other ops:

`        Node* in1 = vector_opd(p, 1);`

When the input is a `PopulateIndex` pattern, then `first->in(1) `gives us the iv-phi, which is a scalar. `vector_opd` would produce a `PopulateIndex` vector.

In the ad-file, we get an error, because we do not expect a scalar as the first operand of the RotateRightV, but a vector.

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Commit messages:
 - fix populate_index, only on sve
 - 8332905

Changes: https://git.openjdk.org/jdk/pull/19445/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19445&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332905
  Stats: 21 lines in 2 files changed: 18 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/19445.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19445/head:pull/19445

PR: https://git.openjdk.org/jdk/pull/19445