Remove constant folding in Painless user tree (#52783)

This change removes constant folding from the Painless user tree. This 
accomplishes two goals. The first is to remove all optimizations from the 
user tree which will at a later time become optimization phases for the ir 
tree. The second is to make the user tree immutable, and this is a step 
toward that since we will no longer remove/modify/replace nodes in the 
user tree during the process of constant folding.

One important note is that the conditional promotion code has changed, 
since the promoteConditional method considered constants (similarly to 
the JVM spec) that are now removed, but this code path was unreachable 
to begin with so the constants were never actually used to determine the 
appropriate promotion.

Author: jdconrad

modules/lang-painless/src/main/java/org/elasticsearch/painless/AnalyzerCaster.java

@@ -520,7 +520,7 @@ public static Class<?> promoteEquality(Class<?> from0, Class<?> from1) {
         return Object.class;
     }
 
-    public static Class<?> promoteConditional(Class<?> from0, Class<?> from1, Object const0, Object const1) {
+    public static Class<?> promoteConditional(Class<?> from0, Class<?> from1) {
         if (from0 == from1) {
             return from0;
         }
@@ -529,123 +529,29 @@ public static Class<?> promoteConditional(Class<?> from0, Class<?> from1, Object
             return def.class;
         }
 
-        if (from0.isPrimitive() && from1.isPrimitive()) {
-            if (from0 == boolean.class && from1 == boolean.class) {
-                return boolean.class;
-            }
-
+        if (from0.isPrimitive() && from0 != boolean.class && from1.isPrimitive() && from1 != boolean.class) {
             if (from0 == double.class || from1 == double.class) {
                 return double.class;
             } else if (from0 == float.class || from1 == float.class) {
                 return float.class;
             } else if (from0 == long.class || from1 == long.class) {
                 return long.class;
+            } else if (from0 == int.class || from1 == int.class) {
+                return int.class;
+            } else if (from0 == char.class) {
+                if (from1 == short.class || from1 == byte.class) {
+                    return int.class;
+                } else {
+                    return null;
+                }
+            } else if (from1 == char.class) {
+                if (from0 == short.class || from0 == byte.class) {
+                return int.class;
             } else {
-                if (from0 == byte.class) {
-                    if (from1 == byte.class) {
-                        return byte.class;
-                    } else if (from1 == short.class) {
-                        if (const1 != null) {
-                            final short constant = (short)const1;
-
-                            if (constant <= Byte.MAX_VALUE && constant >= Byte.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return short.class;
-                    } else if (from1 == char.class) {
-                        return int.class;
-                    } else if (from1 == int.class) {
-                        if (const1 != null) {
-                            final int constant = (int)const1;
-
-                            if (constant <= Byte.MAX_VALUE && constant >= Byte.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return int.class;
-                    }
-                } else if (from0 == short.class) {
-                    if (from1 == byte.class) {
-                        if (const0 != null) {
-                            final short constant = (short)const0;
-
-                            if (constant <= Byte.MAX_VALUE && constant >= Byte.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return short.class;
-                    } else if (from1 == short.class) {
-                        return short.class;
-                    } else if (from1 == char.class) {
-                        return int.class;
-                    } else if (from1 == int.class) {
-                        if (const1 != null) {
-                            final int constant = (int)const1;
-
-                            if (constant <= Short.MAX_VALUE && constant >= Short.MIN_VALUE) {
-                                return short.class;
-                            }
-                        }
-
-                        return int.class;
-                    }
-                } else if (from0 == char.class) {
-                    if (from1 == byte.class) {
-                        return int.class;
-                    } else if (from1 == short.class) {
-                        return int.class;
-                    } else if (from1 == char.class) {
-                        return char.class;
-                    } else if (from1 == int.class) {
-                        if (const1 != null) {
-                            final int constant = (int)const1;
-
-                            if (constant <= Character.MAX_VALUE && constant >= Character.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return int.class;
-                    }
-                } else if (from0 == int.class) {
-                    if (from1 == byte.class) {
-                        if (const0 != null) {
-                            final int constant = (int)const0;
-
-                            if (constant <= Byte.MAX_VALUE && constant >= Byte.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return int.class;
-                    } else if (from1 == short.class) {
-                        if (const0 != null) {
-                            final int constant = (int)const0;
-
-                            if (constant <= Short.MAX_VALUE && constant >= Short.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return int.class;
-                    } else if (from1 == char.class) {
-                        if (const0 != null) {
-                            final int constant = (int)const0;
-
-                            if (constant <= Character.MAX_VALUE && constant >= Character.MIN_VALUE) {
-                                return byte.class;
-                            }
-                        }
-
-                        return int.class;
-                    } else if (from1 == int.class) {
-                        return int.class;
-                    }
+                    return null;
                 }
+            } else {
+                return null;
             }
         }
 

modules/lang-painless/src/main/java/org/elasticsearch/painless/node/AExpression.java

@@ -25,7 +25,6 @@
 import org.elasticsearch.painless.ir.ClassNode;
 import org.elasticsearch.painless.ir.ExpressionNode;
 import org.elasticsearch.painless.lookup.PainlessCast;
-import org.elasticsearch.painless.lookup.PainlessLookupUtility;
 import org.elasticsearch.painless.symbol.ScriptRoot;
 
 import java.util.Objects;
@@ -84,14 +83,6 @@ public abstract class AExpression extends ANode {
      */
     boolean internal = false;
 
-    /**
-     * Set to the value of the constant this expression node represents if
-     * and only if the node represents a constant.  If this is not null
-     * this node will be replaced by an {@link EConstant} during casting
-     * if it's not already one.
-     */
-    Object constant = null;
-
     /**
      * Set to true by {@link ENull} to represent a null value.
      */
@@ -134,97 +125,14 @@ AExpression cast(ScriptRoot scriptRoot, Scope scope) {
         PainlessCast cast = AnalyzerCaster.getLegalCast(location, actual, expected, explicit, internal);
 
         if (cast == null) {
-            if (constant == null || this instanceof EConstant) {
-                // For the case where a cast is not required and a constant is not set
-                // or the node is already an EConstant no changes are required to the tree.
-
-                return this;
-            } else {
-                // For the case where a cast is not required but a
-                // constant is set, an EConstant replaces this node
-                // with the constant copied from this node.  Note that
-                // for constants output data does not need to be copied
-                // from this node because the output data for the EConstant
-                // will already be the same.
-
-                EConstant econstant = new EConstant(location, constant);
-                econstant.analyze(scriptRoot, scope);
-
-                if (!expected.equals(econstant.actual)) {
-                    throw createError(new IllegalStateException("Illegal tree structure."));
-                }
-
-                return econstant;
-            }
+            return this;
         } else {
-            if (constant == null) {
-                // For the case where a cast is required and a constant is not set.
-                // Modify the tree to add an ECast between this node and its parent.
-                // The output data from this node is copied to the ECast for
-                // further reads done by the parent.
-
-                ECast ecast = new ECast(location, this, cast);
-                ecast.statement = statement;
-                ecast.actual = expected;
-                ecast.isNull = isNull;
-
-                return ecast;
-            } else {
-                if (PainlessLookupUtility.isConstantType(expected)) {
-                    // For the case where a cast is required, a constant is set,
-                    // and the constant can be immediately cast to the expected type.
-                    // An EConstant replaces this node with the constant cast appropriately
-                    // from the constant value defined by this node.  Note that
-                    // for constants output data does not need to be copied
-                    // from this node because the output data for the EConstant
-                    // will already be the same.
-
-                    constant = AnalyzerCaster.constCast(location, constant, cast);
-
-                    EConstant econstant = new EConstant(location, constant);
-                    econstant.analyze(scriptRoot, scope);
-
-                    if (!expected.equals(econstant.actual)) {
-                        throw createError(new IllegalStateException("Illegal tree structure."));
-                    }
-
-                    return econstant;
-                } else if (this instanceof EConstant) {
-                    // For the case where a cast is required, a constant is set,
-                    // the constant cannot be immediately cast to the expected type,
-                    // and this node is already an EConstant.  Modify the tree to add
-                    // an ECast between this node and its parent.  Note that
-                    // for constants output data does not need to be copied
-                    // from this node because the output data for the EConstant
-                    // will already be the same.
-
-                    ECast ecast = new ECast(location, this, cast);
-                    ecast.actual = expected;
-
-                    return ecast;
-                } else {
-                    // For the case where a cast is required, a constant is set,
-                    // the constant cannot be immediately cast to the expected type,
-                    // and this node is not an EConstant.  Replace this node with
-                    // an Econstant node copying the constant from this node.
-                    // Modify the tree to add an ECast between the EConstant node
-                    // and its parent.  Note that for constants output data does not
-                    // need to be copied from this node because the output data for
-                    // the EConstant will already be the same.
-
-                    EConstant econstant = new EConstant(location, constant);
-                    econstant.analyze(scriptRoot, scope);
-
-                    if (!actual.equals(econstant.actual)) {
-                        throw createError(new IllegalStateException("Illegal tree structure."));
-                    }
-
-                    ECast ecast = new ECast(location, econstant, cast);
-                    ecast.actual = expected;
-
-                    return ecast;
-                }
-            }
+            ECast ecast = new ECast(location, this, cast);
+            ecast.statement = statement;
+            ecast.actual = expected;
+            ecast.isNull = isNull;
+
+            return ecast;
         }
     }
 }