RFR: 8361842: Move input validation checks to Java for String-related intrinsics [v6]

[Volkan Yazici]

> Validate input in `java.lang.StringCoding` intrinsic Java wrappers, improve their documentation, enhance the checks in the associated IR or assembly code, and adapt them to cause VM crash on invalid input.
> 
> ## Implementation notes
> 
> The goal of the associated umbrella issue [JDK-8156534](https://bugs.openjdk.org/browse/JDK-8156534) is to, for `java.lang.String*` classes,
> 
> 1. Move `@IntrinsicCandidate`-annotated `public` methods<sup>1</sup> (in Java code) to `private` ones, and wrap them with a `public` ["front door" method](https://github.com/openjdk/jdk/pull/24982#discussion_r2087493446)
> 2. Since we moved the `@IntrinsicCandidate` annotation to a new method, intrinsic mappings – i.e., associated `do_intrinsic()` calls in `vmIntrinsics.hpp` – need to be updated too
> 3. Add necessary input validation (range, null, etc.) checks to the newly created public front door method
> 4. Place all input validation checks in the intrinsic code (add if missing!) behind a `VerifyIntrinsicChecks` VM flag
> 
> Following preliminary work needs to be carried out as well:
> 
> 1. Add a new `VerifyIntrinsicChecks` VM flag
> 2. Update `generate_string_range_check` to produce a `HaltNode`.  That is, crash the VM if `VerifyIntrinsicChecks` is set and a Java wrapper fails to spot an invalid input.
> 
> <sup>1</sup>  `@IntrinsicCandidate`-annotated constructors are not subject to this change, since they are a special case.
> 
> ## Functional and performance tests
> 
> - `tier1` (which includes `test/hotspot/jtreg/compiler/intrinsics/string`) passes on several platforms. Further tiers will be executed after integrating reviewer feedback.
> 
> - Performance impact is still actively monitored using `test/micro/org/openjdk/bench/java/lang/String{En,De}code.java`, among other tests. If you have suggestions on benchmarks, please share in the comments.
> 
> ## Verification of the VM crash
> 
> I've tested the VM crash scenario as follows:
> 
> 1. Created the following test program:
> 
> public class StrIntri {
>     public static void main(String[] args) {
>         Exception lastException = null;
>         for (int i = 0; i < 1_000_000; i++) {
>             try {
>                 jdk.internal.access.SharedSecrets.getJavaLangAccess().countPositives(new byte[]{1,2,3}, 2, 5);
>             } catch (Exception exception) {
>                 lastException = exception;
>             }
>         }
>         if (lastException != null) {
>             lastException.printStackTrace();
>         } else {
>             System.out.println("completed");
>         }
>     }
> }
> ...

Volkan Yazici has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Add test verifying the effectiveness of `VerifyIntrinsicChecks`

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25998/files
  - new: https://git.openjdk.org/jdk/pull/25998/files/8941e6b6..bcb073cb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25998&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25998&range=04-05

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25998.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25998/head:pull/25998

PR: https://git.openjdk.org/jdk/pull/25998