RFR: 8298632: [TESTBUG] Add IR checks in jtreg vectorization tests [v5]

[Pengfei Li]

> In JDK-8183390, we introduced a new auto-vectorization testing framework in hotspot jtreg tests. The new framework provides us a much simpler way to add new test cases of auto-vectorizable loops. But the previous patch just added a check of the correctness of the result after vectorization. There is no check about whether the code is vectorized or not.
> 
> This patch adds IR checks to verify C2's vectorization ability on test cases inside this framework. With this patch, each test method annotated with `@Test` is verified in two ways. First, it's invoked twice and the return results from the interpreter and C2 compiled code are compared. Second, the count of expected vector IR is checked by the IR framework if the test method has IR rule annotation.
> 
> Ideally, we should check IR rules on all platforms. But in practice, the vectorization ability can be quite different on different platforms, or different generations of CPUs of one platform. So in this patch, we only add vectorizable checks for AArch64. Checks for other platforms (such as x86) can still be added later with more CPU feature conditions. We also add some negative rules (or in-vectorizable rules) with `@IR(failOn=...` on cases that should not be vectorized on any platform.
> 
> A few more test cases are added within this patch as well.
> 
> We tested the new IR rules on below kinds of CPUs.
> - AArch64 w/ 512-bit SVE
> - AArch64 w/ 128-bit SVE
> - AArch64 w/o SVE (NEON only)
> - x86

Pengfei Li has updated the pull request incrementally with one additional commit since the last revision:

  Add some more exact IR checks mainly for x86

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11687/files
  - new: https://git.openjdk.org/jdk/pull/11687/files/faa95c53..54a2dd94

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11687&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11687&range=03-04

  Stats: 221 lines in 21 files changed: 26 ins; 0 del; 195 mod
  Patch: https://git.openjdk.org/jdk/pull/11687.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11687/head:pull/11687

PR: https://git.openjdk.org/jdk/pull/11687