Only use uncached instance of JNI helper node

Author: fangerer

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/hpy/jni/GraalHPyJNICallHelperFunctionNode.java

@@ -55,6 +55,9 @@ final class GraalHPyJNICallHelperFunctionNode extends HPyCallHelperFunctionNode
 
     static final GraalHPyJNICallHelperFunctionNode UNCACHED = new GraalHPyJNICallHelperFunctionNode();
 
+    private GraalHPyJNICallHelperFunctionNode() {
+    }
+
     @Override
     protected Object execute(GraalHPyContext context, GraalHPyNativeSymbol name, Object[] args) {
         assert context.getBackend() instanceof GraalHPyJNIContext;
@@ -67,11 +70,11 @@ protected Object execute(GraalHPyContext context, GraalHPyNativeSymbol name, Obj
 
     @Override
     public NodeCost getCost() {
-        return this == UNCACHED ? NodeCost.MEGAMORPHIC : NodeCost.NONE;
+        return NodeCost.MONOMORPHIC;
     }
 
     @Override
     public boolean isAdoptable() {
-        return this != UNCACHED;
+        return false;
     }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/hpy/jni/GraalHPyJNIContext.java

@@ -487,7 +487,7 @@ protected void setNativeCache(long cachePtr) {
 
     @Override
     public HPyCallHelperFunctionNode createCallHelperFunctionNode() {
-        return new GraalHPyJNICallHelperFunctionNode();
+        return GraalHPyJNICallHelperFunctionNode.UNCACHED;
     }
 
     @Override
@@ -497,7 +497,7 @@ public HPyCallHelperFunctionNode getUncachedCallHelperFunctionNode() {
 
     @Override
     public HPyFromCharPointerNode createFromCharPointerNode() {
-        throw CompilerDirectives.shouldNotReachHere("cached HPyJNIFromCharPointerNode is not available");
+        return HPyJNIFromCharPointerNode.UNCACHED;
     }
 
     @Override