RFR: 8342387: C2 SuperWord: refactor and improve compiler/loopopts/superword/TestDependencyOffsets.java [v3]

[Emanuel Peter]

> I want to refactor `TestDependencyOffsets.java` using the `CompileFramework`.
> 
> Reasons:
> - I soon need to modify the IR rules in this test soon anyway (https://github.com/openjdk/jdk/pull/21521), and so a refactor might be good to do first.
> - The generator script used to be a `generator.py`, stored not on `git` but `JBS`. Not great. Now we have it in Java code, and maintenance is easier.
> - Since I first wrote that test, I have now introduced the `IRNode.VECTOR_SIZE`. This allows:
>   - Simplifying the logic for the IR rules (removed the `IRRange` and `IRBool`, and the `Platform`).
>   - Strengthening the rules.
> - I was able to add `random` offsets. This means we have better coverage, and do not rely on just hand-crafted values.
> 
> I extensively use `String.format` and `StringBuilder`... would be nicer to have string-templates but they don't exist yet.
> 
> Recommendation for review: the old file was huge. Finding the new code in the diff can be hard. I would start by only reading the new file.
> 
> Ah. And about runtime of the test. On my machine I get this (in ms):
> 
> Generate: 27
> Compile:  5845
> Run:      23435
> 
> Test generation is negligible. 6sec on compilation, 20+sec on execution. I think that is an ok balance, at least we can say that generation and compilation only take about 1/6 of total time - an acceptable overhead I would say.

Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:

  Suggestions by Christian

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21541/files
  - new: https://git.openjdk.org/jdk/pull/21541/files/460176c0..46b95030

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21541&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21541&range=01-02

  Stats: 47 lines in 1 file changed: 0 ins; 1 del; 46 mod
  Patch: https://git.openjdk.org/jdk/pull/21541.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21541/head:pull/21541

PR: https://git.openjdk.org/jdk/pull/21541