Pass-thru ShenandoahLoadRefBarrier and ShenandoahSATBBarrier flags from HotSpot

Author: Roman Kennke

compiler/src/org.graalvm.compiler.hotspot/src/org/graalvm/compiler/hotspot/GraalHotSpotVMConfig.java

@@ -197,6 +197,8 @@ public boolean inlineNotifyAll() {
     public final boolean useG1GC = getFlag("UseG1GC", Boolean.class);
     public final boolean useCMSGC = getFlag("UseConcMarkSweepGC", Boolean.class, false, JDK < 14); // JDK-8231559
     public final boolean useShenandoahGC = getFlag("UseShenandoahGC", Boolean.class);
+    public final boolean shenandoahLoadRefBarrier = getFlag("ShenandoahLoadRefBarrier", Boolean.class);
+    public final boolean shenandoahSATBBarrier = getFlag("ShenandoahSATBBarrier", Boolean.class);
 
     public final int allocatePrefetchStyle = getFlag("AllocatePrefetchStyle", Integer.class);
     public final int allocatePrefetchInstr = getFlag("AllocatePrefetchInstr", Integer.class);

compiler/src/org.graalvm.compiler.hotspot/src/org/graalvm/compiler/hotspot/HotSpotGraalRuntime.java

@@ -254,7 +254,7 @@ public enum HotSpotGC {
         Parallel(true, JDK >= 11, "UseParallelGC", true, "UseParallelOldGC", JDK < 15, "UseParNewGC", JDK < 10),
         CMS(true, JDK >= 11 && JDK <= 14, "UseConcMarkSweepGC", JDK < 14),
         G1(true, JDK >= 11, "UseG1GC", true),
-        Shenandoah(true, JDK >= 11, "UseShenandoahGC", true),
+        Shenandoah(true, JDK >= 11, "UseShenandoahGC", JDK >= 11),
 
         // Unsupported GCs
         Epsilon(false, JDK >= 11, "UseEpsilonGC", JDK >= 11),

compiler/src/org.graalvm.compiler.hotspot/src/org/graalvm/compiler/hotspot/meta/HotSpotPlatformConfigurationProvider.java

@@ -76,7 +76,7 @@ protected boolean writeRequiresPostBarrier(FixedAccessNode node, ValueNode writt
                 }
             };
         } else if (config.useShenandoahGC) {
-            return new ShenandoahBarrierSet(config, objectArrayType, referentField);
+            return new ShenandoahBarrierSet(config.shenandoahSATBBarrier, config.shenandoahLoadRefBarrier, objectArrayType, referentField);
         } else {
             return new CardTableBarrierSet(objectArrayType) {
                 @Override

compiler/src/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/gc/ShenandoahBarrierSet.java

@@ -51,10 +51,14 @@
 public class ShenandoahBarrierSet implements BarrierSet {
     private final ResolvedJavaType objectArrayType;
     private final ResolvedJavaField referentField;
+    private final boolean useLRB;
+    private final boolean useSATB;
 
-    public ShenandoahBarrierSet(GraalHotSpotVMConfig config, ResolvedJavaType objectArrayType, ResolvedJavaField referentField) {
+    public ShenandoahBarrierSet(boolean useSATB, boolean useLRB, ResolvedJavaType objectArrayType, ResolvedJavaField referentField) {
         this.objectArrayType = objectArrayType;
         this.referentField = referentField;
+        this.useSATB = useSATB;
+        this.useLRB = useLRB;
     }
 
     @Override
@@ -68,18 +72,20 @@ public void addBarriers(FixedAccessNode n) {
             LoweredAtomicReadAndWriteNode atomic = (LoweredAtomicReadAndWriteNode) n;
             addWriteBarriers(atomic, atomic.getNewValue(), null, true, atomic.getNullCheck());
         } else if (n instanceof AbstractCompareAndSwapNode) {
+            GraalError.unimplemented();
             AbstractCompareAndSwapNode cmpSwap = (AbstractCompareAndSwapNode) n;
             addWriteBarriers(cmpSwap, cmpSwap.getNewValue(), cmpSwap.getExpectedValue(), false, false);
         } else if (n instanceof ArrayRangeWrite) {
+            GraalError.unimplemented();
             addArrayRangeBarriers((ArrayRangeWrite) n);
         } else {
             GraalError.guarantee(n.getBarrierType() == BarrierType.NONE, "missed a node that requires a GC barrier: %s", n.getClass());
         }
     }
 
-    private static void addReadNodeBarriers(ReadNode node) {
+    private void addReadNodeBarriers(ReadNode node) {
         ValueNode value = node;
-        if (node.getBarrierType() != BarrierType.NONE) {
+        if (node.getBarrierType() != BarrierType.NONE && useLRB) {
             StructuredGraph graph = node.graph();
             ShenandoahLoadReferenceBarrier lrb = graph.add(new ShenandoahLoadReferenceBarrier(node));
             value = lrb;
@@ -105,7 +111,7 @@ private void addWriteBarriers(FixedAccessNode node, ValueNode writtenValue, Valu
                 if (isObjectValue(writtenValue)) {
                     StructuredGraph graph = node.graph();
                     boolean init = node.getLocationIdentity().isInit();
-                    if (!init) {
+                    if (!init && useSATB) {
                         // The pre barrier does nothing if the value being read is null, so it can
                         // be explicitly skipped when this is an initializing store.
                         addPreWriteBarrier(node, node.getAddress(), expectedValue, doLoad, nullCheck, graph);

compiler/src/org.graalvm.compiler.replacements/src/org/graalvm/compiler/replacements/gc/ShenandoahBarrierSnippets.java

@@ -172,10 +172,10 @@ public void shenandoahArrayRangePreWriteBarrier(AddressNode.Address address, int
     public Object shenandoahLoadReferenceBarrier(Object value) {
         Word thread = getThread();
         verifyOop(value);
-        byte gcStateValue = thread.readByte(gcStateOffset(), GC_STATE_LOCATION);
-        if (probability(NOT_FREQUENT_PROBABILITY, (gcStateValue & HAS_FORWORDED) != (byte) 0)) {
-            return shenandoahLoadReferenceBarrierStub(value);
-        }
+//        byte gcStateValue = thread.readByte(gcStateOffset(), GC_STATE_LOCATION);
+//        if (probability(NOT_FREQUENT_PROBABILITY, (gcStateValue & HAS_FORWORDED) != (byte) 0)) {
+//            return shenandoahLoadReferenceBarrierStub(value);
+//        }
         return value;
     }