/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.dx.cf.code;
import com.android.dx.rop.type.Type;
import com.android.dx.rop.type.TypeBearer;
/**
* Utility methods to merge various frame information.
*/
public final class Merger {
/**
* Merges two frame types.
*
* @param ft1 {@code non-null;} a frame type
* @param ft2 {@code non-null;} another frame type
* @return {@code non-null;} the result of merging the two types
*/
public static TypeBearer mergeType(TypeBearer ft1, TypeBearer ft2) {
if ((ft1 == null) || ft1.equals(ft2)) {
return ft1;
} else if (ft2 == null) {
return null;
} else {
Type type1 = ft1.getType();
Type type2 = ft2.getType();
if (type1 == type2) {
return type1;
} else if (type1.isReference() && type2.isReference()) {
if (type1 == Type.KNOWN_NULL) {
/*
* A known-null merges with any other reference type to
* be that reference type.
*/
return type2;
} else if (type2 == Type.KNOWN_NULL) {
/*
* The same as above, but this time it's type2 that's
* the known-null.
*/
return type1;
} else if (type1.isArray() && type2.isArray()) {
TypeBearer componentUnion =
mergeType(type1.getComponentType(),
type2.getComponentType());
if (componentUnion == null) {
/*
* At least one of the types is a primitive type,
* so the merged result is just Object.
*/
return Type.OBJECT;
}
return ((Type) componentUnion).getArrayType();
} else {
/*
* All other unequal reference types get merged to be
* Object in this phase. This is fine here, but it
* won't be the right thing to do in the verifier.
*/
return Type.OBJECT;
}
} else if (type1.isIntlike() && type2.isIntlike()) {
/*
* Merging two non-identical int-like types results in
* the type int.
*/
return Type.INT;
} else {
return null;
}
}
}
}