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Description: [s390x] G1 barrier compareAndExchange does not return old value when compareExchange fails
Correct typo in g1CompareAndExchangeP
Author: Vladimir Petko <vladimir.petko@canonical.com>
Origin: upstream, https://github.com/openjdk/jdk/pull/27857
Bug: https://bugs.openjdk.org/browse/JDK-8370049
Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/openjdk-25/+bug/2127750
Last-Update: 2025-10-20
diff --git a/src/hotspot/cpu/s390/gc/g1/g1_s390.ad b/src/hotspot/cpu/s390/gc/g1/g1_s390.ad
index 7aed374fdae..000ac3bc5ba 100644
--- a/src/hotspot/cpu/s390/gc/g1/g1_s390.ad
+++ b/src/hotspot/cpu/s390/gc/g1/g1_s390.ad
@@ -356,7 +356,7 @@ instruct g1CompareAndExchangeP(iRegP mem_ptr, rarg5RegP oldval, iRegP_N2P newval
__ z_lgr($res$$Register, $oldval$$Register); // previous content
- __ z_csg($oldval$$Register, $newval$$Register, 0, $mem_ptr$$reg);
+ __ z_csg($res$$Register, $newval$$Register, 0, $mem_ptr$$reg);
write_barrier_post(masm, this,
$mem_ptr$$Register /* store_addr */,
diff --git a/test/hotspot/jtreg/compiler/gcbarriers/TestG1BarrierGeneration.java b/test/hotspot/jtreg/compiler/gcbarriers/TestG1BarrierGeneration.java
index 01e015d50cb..c1e2dd7a112 100644
--- a/test/hotspot/jtreg/compiler/gcbarriers/TestG1BarrierGeneration.java
+++ b/test/hotspot/jtreg/compiler/gcbarriers/TestG1BarrierGeneration.java
@@ -880,6 +880,16 @@ public void runAtomicTests() {
Asserts.assertEquals(oldVal, oldVal2);
Asserts.assertEquals(o.f, newVal);
}
+ {
+ Outer o = new Outer();
+ Object oldVal = new Object();
+ o.f = oldVal;
+ Object cmpVal = new Object();
+ Object newVal = new Object();
+ Object oldVal2 = testCompareAndExchange(o, cmpVal, newVal);
+ Asserts.assertEquals(oldVal2, oldVal);
+ Asserts.assertEquals(o.f, oldVal);
+ }
{
Outer o = new Outer();
Object oldVal = new Object();
@@ -889,6 +899,16 @@ public void runAtomicTests() {
Asserts.assertTrue(b);
Asserts.assertEquals(o.f, newVal);
}
+ {
+ Outer o = new Outer();
+ Object oldVal = new Object();
+ o.f = oldVal;
+ Object cmpVal = new Object();
+ Object newVal = new Object();
+ boolean b = testCompareAndSwap(o, cmpVal, newVal);
+ Asserts.assertFalse(b);
+ Asserts.assertEquals(o.f, oldVal);
+ }
{
Outer o = new Outer();
Object oldVal = new Object();
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