don't use regex matching to compute reverse method name

Author: lukasstadler

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/call/special/LookupAndCallBinaryNode.java

@@ -110,9 +110,9 @@ public static LookupAndCallBinaryNode create(String name) {
         return LookupAndCallBinaryNodeGen.create(name, null, null);
     }
 
-    public static LookupAndCallBinaryNode createReversible(String name, Supplier<NotImplementedHandler> handlerFactory) {
-        assert name.startsWith("__");
-        return LookupAndCallBinaryNodeGen.create(name, name.replaceFirst("__", "__r"), handlerFactory);
+    public static LookupAndCallBinaryNode createReversible(String name, String reverseName, Supplier<NotImplementedHandler> handlerFactory) {
+        assert name.startsWith("__") && reverseName.startsWith("__r");
+        return LookupAndCallBinaryNodeGen.create(name, reverseName, handlerFactory);
     }
 
     public static LookupAndCallBinaryNode create(String name, String rname) {

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/expression/BinaryArithmetic.java

@@ -67,11 +67,14 @@ public enum BinaryArithmetic {
     Pow(SpecialMethodNames.__POW__, "**");
 
     private final String methodName;
+    private final String reverseMethodName;
     private final String operator;
     private final Supplier<NotImplementedHandler> notImplementedHandler;
 
     BinaryArithmetic(String methodName, String operator) {
         this.methodName = methodName;
+        assert methodName.startsWith("__");
+        this.reverseMethodName = "__r" + methodName.substring(2);
         this.operator = operator;
         this.notImplementedHandler = () -> new NotImplementedHandler() {
             @Override
@@ -112,10 +115,10 @@ public NodeCost getCost() {
     }
 
     public ExpressionNode create(ExpressionNode left, ExpressionNode right) {
-        return new BinaryArithmeticExpression(LookupAndCallBinaryNode.createReversible(methodName, notImplementedHandler), left, right);
+        return new BinaryArithmeticExpression(LookupAndCallBinaryNode.createReversible(methodName, reverseMethodName, notImplementedHandler), left, right);
     }
 
     public LookupAndCallBinaryNode create() {
-        return LookupAndCallBinaryNode.createReversible(methodName, notImplementedHandler);
+        return LookupAndCallBinaryNode.createReversible(methodName, reverseMethodName, notImplementedHandler);
     }
 }