8202095: JFR TestBiasedLockRevocationEvents should cope with multiple events during a single safepoint
Reviewed-by: mgronlun, egahlin
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/*
* @test TestMembarDependencies
* @bug 8172850
* @summary Tests correct scheduling of memory loads around MembarVolatile emitted by GC barriers.
* @library /test/lib /
* @modules java.base/jdk.internal.misc
* java.management
* @run driver compiler.membars.TestMembarDependencies
*/
package compiler.membars;
import jdk.test.lib.process.OutputAnalyzer;
import jdk.test.lib.process.ProcessTools;
public class TestMembarDependencies {
private static TestMembarDependencies f1;
private static TestMembarDependencies f2;
public static void main(String args[]) throws Exception {
if (args.length == 0) {
// For debugging, add "-XX:+TraceOptoPipelining"
OutputAnalyzer oa = ProcessTools.executeTestJvm("-XX:+IgnoreUnrecognizedVMOptions",
"-XX:-TieredCompilation", "-XX:-BackgroundCompilation", "-XX:+PrintOpto",
"-XX:CompileCommand=compileonly,compiler.membars.TestMembarDependencies::test*",
"-XX:CompileCommand=dontinline,compiler.membars.TestMembarDependencies::test_m1",
TestMembarDependencies.class.getName(), "run");
// C2 should not crash or bail out from compilation
oa.shouldHaveExitValue(0);
oa.shouldNotMatch("Bailout: Recompile without subsuming loads");
System.out.println(oa.getOutput());
} else {
f2 = new TestMembarDependencies();
// Trigger compilation of test1 and test2
for (int i = 0; i < 10_000; ++i) {
f2.test1(f2);
f2.test2(f2);
}
}
}
public void test_m1() { }
public void test_m2() { }
public void test1(TestMembarDependencies obj) {
// Try/catch/finally is used to create a CFG block without a test + jmpCon
// allowing GCM to schedule the testN_mem_reg0 instruction into that block.
try {
// Method call defines memory state that is then
// used by subsequent instructions/blocks (see below).
test_m1();
} catch (Exception e) {
} finally {
// Oop write to field emits a GC post-barrier with a MembarVolatile
// which has a wide memory effect (kills all memory). This creates an
// anti-dependency on all surrounding memory loads.
f1 = obj;
}
// The empty method m2 is inlined but the null check of f2 remains. It is encoded
// as CmpN(LoadN(MEM), NULL) where MEM is the memory after the call to test_m1().
// This is matched to testN_mem_reg0 on x86 which is scheduled before the barrier
// in the try/catch block due to the anti-dependency on the MembarVolatile.
// C2 crashes in the register allocator when trying to spill the flag register
// to keep the result of the testN instruction live from the try/catch block
// until it is here.
f2.test_m2();
}
public void test2(TestMembarDependencies obj) {
// Same as test1 but without try/catch/finally.
// This causes C2 to bail out in block local scheduling because testN_mem_reg0 is
// scheduled into a block that already contains another test + jmpCon instruction.
test_m1();
f1 = obj;
f2.test_m2();
}
}