RFR: 8309266: C2: assert(final_con == (jlong)final_int) failed: final value should be integer

[Daohan Qu]

This patch should fix [JDK-8309266](https://bugs.openjdk.org/browse/JDK-8309266). A `jtreg` test is also added. I'd appreciate any comments and reviews. Thanks in advance!

## Problem Analysis

For the following program,

public class Test {

    static boolean flag;

    public static void main(String[] args) {
        for (int i = 0; i < 10000; i++) {
            flag = !flag;
            test();
        }
    }

    public static void test() {
        int limit = flag ? Integer.MAX_VALUE : 1000;

        int i = 0;
        while (i < limit) {
            i += 3;
            if (flag) {
                return;
            }
        }
    }
}

A `LoopLimitNode` will be generated and its `Limit` input is a `PhiNode`, as depicted in the following picture.

<img width="384" alt="phi_as_limit" src="https://github.com/openjdk/jdk/assets/18374295/c561bb09-9789-45c2-8fa8-5bc690ea8046">

During `PhaseCCP`, the `LoopLimitNode::Value()` tries to calculate the constant final value:
https://github.com/openjdk/jdk/blob/16ebf47fe3b0fac7b67acfa589a26abf8843306b/src/hotspot/share/opto/loopnode.cpp#L2289-L2301

The problem is that the assertion in `line 2299` could fail during CCP though it must hold true at the end of CCP. Here is the reason: `PhaseCCP` initializes all nodes with the type `TOP` and iterates in an "arbitrary" order. The following order may happen:

28 IfTrue => 34 Region => 36 Phi => 195 LoopLimit => ... => 29 IfFalse

1. In `ProjNode::Value()` (`IfTrue` inherits it), the type of `IfTrue` is set to `Type::CONTROL`
https://github.com/openjdk/jdk/blob/fa791119f0b73cd1e110d6a62d3bed58fee5740a/src/hotspot/share/opto/multnode.cpp#L168-L171

2. In `PhiNode::Value()`, only `28 IfTrue`'s correspondence `33 ConI` gets merged (as `29 IfFalse` has not been dealt with yet), then it has a value of `int:max`.
https://github.com/openjdk/jdk/blob/fa791119f0b73cd1e110d6a62d3bed58fee5740a/src/hotspot/share/opto/cfgnode.cpp#L1269-L1277

3. In `LoopLimitNode::Value()`, it finds its `Limit` input `36 Phi` is constant, which triggers the assertion, and the assertion fails since the final value calculated from that constant limit (`int:max`) overflows.

## Solution
Move the overflow check to the end of CCP, where it must not fail.

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

Commit messages:
 - Add a jtreg test for this bug
 - Move final value overflow check of LoopLimitNode to the end of CCP
 - Add query and cast method for LoopLimitNode

Changes: https://git.openjdk.org/jdk/pull/14353/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14353&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309266
  Stats: 119 lines in 5 files changed: 110 ins; 4 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/14353.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14353/head:pull/14353

PR: https://git.openjdk.org/jdk/pull/14353