RFR: 8350563: C2 compilation fails because PhaseCCP does not reach a fixpoint [v8]

[Liam Miller-Cushon]

On Mon, 7 Apr 2025 07:01:57 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Liam Miller-Cushon has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 15 additional commits since the last revision:
>> 
>>  - Add -XX:+UnlockDiagnosticVMOptions
>>  - Check type before uncasting
>>    
>>    A child phi node may transition from con to non-con, making the AND node transition back from "0" to its current type. If that current type is still TOP we're in violation of monotonicity. Therefore, don't apply optimization if AND is not integer yet.
>>  - Merge commit '9bb804b14e1' into JDK-8350563
>>  - Explicitly check for OP_Con instead of TypeInteger::is_con.
>>    
>>     322  Phi  === 303 119 255  [[ 399 388 351 751 366 377 ]]  #int:-256..127 !jvms: Integer::parseInt @ bci:151 (line 625)
>>    
>>     While this Phi dumps as "#int:-256..127", `phase->type(expr)` returns a type that is_con -256.
>>  - Update test/hotspot/jtreg/compiler/ccp/TestAndConZeroCCP.java
>>    
>>    Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>
>>  - Merge remote-tracking branch 'origin/master' into JDK-8350563
>>  - Reformat test and update package to ccp
>>  - Review comments
>>  - Update test/hotspot/jtreg/compiler/c2/TestAndConZeroCCP.java
>>    
>>    Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
>>  - copyright
>>  - ... and 5 more: https://git.openjdk.org/jdk/compare/5f51fee4...23119e18
>
> test/hotspot/jtreg/compiler/ccp/TestAndConZeroMonotonic.java line 35:
> 
>> 33: public class TestAndConZeroMonotonic {
>> 34: 
>> 35:     public static void main(String[] args) {
> 
> Since it's quite an easy test, I suggest to merge the two test files together by calling `Integer::parseInt()` directly instead. You can just add another `@run` statement.

Done

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PR Review Comment: https://git.openjdk.org/jdk/pull/23871#discussion_r2031450257