8355299: [lworld] C2 compilation fails with "unexpected yanked node"

Author: TobiHartmann

src/hotspot/share/opto/inlinetypenode.cpp

@@ -617,10 +617,12 @@ void InlineTypeNode::convert_from_payload(GraphKit* kit, BasicType bt, Node* pay
         }
         value = gvn->transform(new CastI2NNode(kit->control(), value));
         value = gvn->transform(new DecodeNNode(value, val_type->make_narrowoop()));
-        // TODO 8350865 Should we add the membar to the CastI2N and give it a type?
         value = gvn->transform(new CastPPNode(kit->control(), value, val_type, ConstraintCastNode::UnconditionalDependency));
-        // Prevent the CastI2N from floating below a safepoint
-        kit->insert_mem_bar(Op_MemBarVolatile, value);
+
+        // Similar to CheckCastPP nodes with raw input, CastI2N nodes require special handling in 'PhaseCFG::schedule_late' to ensure the
+        // register allocator does not move the CastI2N below a safepoint. This is necessary to avoid having the raw pointer span a safepoint,
+        // making it opaque to the GC. Unlike CheckCastPPs, which need extra handling in 'Scheduling::ComputeRegisterAntidependencies' due to
+        // scalarization, CastI2N nodes are always used by a load if scalarization happens which inherently keeps them pinned above the safepoint.
 
         if (ft->is_inlinetype()) {
           GrowableArray<ciType*> visited;

test/hotspot/jtreg/compiler/valhalla/inlinetypes/TestGenerated.java

@@ -23,7 +23,7 @@
 
 /**
  * @test
- * @bug 8260034 8260225 8260283 8261037 8261874 8262128 8262831 8306986
+ * @bug 8260034 8260225 8260283 8261037 8261874 8262128 8262831 8306986 8355299
  * @summary A selection of generated tests that triggered bugs not covered by other tests.
  * @enablePreview
  * @modules java.base/jdk.internal.value
@@ -32,6 +32,8 @@
  *                   compiler.valhalla.inlinetypes.TestGenerated
  * @run main/othervm -Xbatch -XX:-UseArrayFlattening
  *                   compiler.valhalla.inlinetypes.TestGenerated
+ * @run main/othervm -Xbatch -XX:+UseNullableValueFlattening -XX:+UseAtomicValueFlattening -XX:+UseNonAtomicValueFlattening
+ *                   compiler.valhalla.inlinetypes.TestGenerated
  */
 
 package compiler.valhalla.inlinetypes;