Adapt JDK-8323497: On x64, use 32-bit immediate moves for narrow klass base if possible

Author: mur47x111

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/schedule/SchedulePhase.java

@@ -735,16 +735,12 @@ protected static boolean isImplicitNullOpportunity(Node currentNode, HIRBlock bl
             if (!supportsImplicitNullChecks) {
                 return false;
             }
-            if (currentNode instanceof FloatingReadNode) {
-                FloatingReadNode floatingReadNode = (FloatingReadNode) currentNode;
+            if (currentNode instanceof FloatingReadNode floatingReadNode) {
                 Node pred = block.getBeginNode().predecessor();
-                if (pred instanceof IfNode) {
-                    IfNode ifNode = (IfNode) pred;
-                    if (ifNode.condition() instanceof IsNullNode && ifNode.getTrueSuccessorProbability() == 0.0) {
-                        IsNullNode isNullNode = (IsNullNode) ifNode.condition();
-                        if (getUnproxifiedUncompressed(floatingReadNode.getAddress().getBase()) == getUnproxifiedUncompressed(isNullNode.getValue())) {
-                            return true;
-                        }
+                if (pred instanceof IfNode ifNode) {
+                    if (ifNode.condition() instanceof IsNullNode isNullNode && ifNode.getTrueSuccessorProbability() == 0.0) {
+                        ValueNode base = floatingReadNode.getAddress().getBase();
+                        return base != null && getUnproxifiedUncompressed(base) == getUnproxifiedUncompressed(isNullNode.getValue());
                     }
                 }
             }