RFR: 8370049: [s390x] G1 barrier compareAndExchange does not return old value when compareExchange fails

[Roberto Castañeda Lozano]

On Thu, 16 Oct 2025 22:55:56 GMT, Vladimir Petko <vpetko at openjdk.org> wrote:

> This PR fixes typo in `src/hotspot/cpu/s390/gc/g1/g1_s390.ad` that caused `compareAndExchange` return expected value instead of old value when compareAndExchange failed.
> It updates jtreg test to include negative tests for compareAndExchange and compareAndSwap g1 barriers.
> 
> Testing (s390x) :
> 
> ==============================
> Test summary
> ==============================
>    TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
>    jtreg:test/hotspot/jtreg/compiler/gcbarriers/TestG1BarrierGeneration.java
>                                                          1     1     0     0     0   
> ==============================
> TEST SUCCESS
> 
> Tier1 summary:
> 
> ==============================
> Test summary
> ==============================
>    TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
>    jtreg:test/hotspot/jtreg:tier1                     3118  2466     0     0   652   
>    jtreg:test/jdk:tier1                               2518  2418     0     0   100   
>    jtreg:test/langtools:tier1                         4672  4662     0     0    10   
>    jtreg:test/jaxp:tier1                                 0     0     0     0     0   
>    jtreg:test/lib-test:tier1                            38    38     0     0     0   
> ==============================
> TEST SUCCESS
> 
> 
> Tier 2 tests contain unrelated failures:
> 
> ==============================
> Test summary
> ==============================
>    TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
>>> jtreg:test/hotspot/jtreg:tier2                      960   766     1     0   193 <<
>>> jtreg:test/jdk:tier2                               4455  4203     5     0   247 <<
>    jtreg:test/langtools:tier2                           14    12     0     0     2   
>    jtreg:test/jaxp:tier2                               517   516     0     0     1   
>    jtreg:test/docs:tier2                                 4     0     0     0     4   
> ==============================
> TEST FAILURE
> 
> jtreg:test/hotspot/jtreg:tier2:
> 1. ``applications/ctw/modules/jdk_jfr.java                                                      Failed. Execution failed: `main' threw exception: java.lang.AssertionError: There were 1 errors:[{modules_jdk_jfr_0: failed during compilation of class #226 : jdk/jfr/internal/jfc/JFC}]`` - existing issue https://bugs.openjdk.org/browse/JDK-8352567 
> 
> jtreg:test/jdk:tier2:
> 1. ``java/net/Inet6Address/B6206527.java                                                                  ...

Test results look good!

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

Marked as reviewed by rcastanedalo (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27857#pullrequestreview-3349854502