diff -r 000000000000 -r c880a8a8803b rt/emul/compact/src/main/java/sun/invoke/util/VerifyType.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/sun/invoke/util/VerifyType.java Sat Aug 09 11:11:13 2014 +0200 @@ -0,0 +1,194 @@ +/* + * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. Oracle designates this + * particular file as subject to the "Classpath" exception as provided + * by Oracle in the LICENSE file that accompanied this code. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ + +package sun.invoke.util; + +import java.lang.invoke.MethodType; +import sun.invoke.empty.Empty; + +/** + * This class centralizes information about the JVM verifier + * and its requirements about type correctness. + * @author jrose + */ +public class VerifyType { + + private VerifyType() { } // cannot instantiate + + /** + * True if a value can be stacked as the source type and unstacked as the + * destination type, without violating the JVM's type consistency. + * + * @param src the type of a stacked value + * @param dst the type by which we'd like to treat it + * @return whether the retyping can be done without motion or reformatting + */ + public static boolean isNullConversion(Class src, Class dst) { + if (src == dst) return true; + // Verifier allows any interface to be treated as Object: + if (dst.isInterface()) dst = Object.class; + if (src.isInterface()) src = Object.class; + if (src == dst) return true; // check again + if (dst == void.class) return true; // drop any return value + if (isNullType(src)) return !dst.isPrimitive(); + if (!src.isPrimitive()) return dst.isAssignableFrom(src); + if (!dst.isPrimitive()) return false; + // Verifier allows an int to carry byte, short, char, or even boolean: + Wrapper sw = Wrapper.forPrimitiveType(src); + if (dst == int.class) return sw.isSubwordOrInt(); + Wrapper dw = Wrapper.forPrimitiveType(dst); + if (!sw.isSubwordOrInt()) return false; + if (!dw.isSubwordOrInt()) return false; + if (!dw.isSigned() && sw.isSigned()) return false; + return dw.bitWidth() > sw.bitWidth(); + } + + /** + * Specialization of isNullConversion to reference types. + * @param src the type of a stacked value + * @param dst the reference type by which we'd like to treat it + * @return whether the retyping can be done without a cast + */ + public static boolean isNullReferenceConversion(Class src, Class dst) { + assert(!dst.isPrimitive()); + if (dst.isInterface()) return true; // verifier allows this + if (isNullType(src)) return true; + return dst.isAssignableFrom(src); + } + + /** + * Is the given type java.lang.Null or an equivalent null-only type? + */ + public static boolean isNullType(Class type) { + if (type == null) return false; + return type == NULL_CLASS + // This one may also be used as a null type. + // TO DO: Decide if we really want to legitimize it here. + // Probably we do, unless java.lang.Null really makes it into Java 7 + //|| type == Void.class + // Locally known null-only class: + || type == Empty.class + ; + } + private static final Class NULL_CLASS; + static { + Class nullClass = null; + try { + nullClass = Class.forName("java.lang.Null"); + } catch (ClassNotFoundException ex) { + // OK, we'll cope + } + NULL_CLASS = nullClass; + } + + /** + * True if a method handle can receive a call under a slightly different + * method type, without moving or reformatting any stack elements. + * + * @param call the type of call being made + * @param recv the type of the method handle receiving the call + * @return whether the retyping can be done without motion or reformatting + */ + public static boolean isNullConversion(MethodType call, MethodType recv) { + if (call == recv) return true; + int len = call.parameterCount(); + if (len != recv.parameterCount()) return false; + for (int i = 0; i < len; i++) + if (!isNullConversion(call.parameterType(i), recv.parameterType(i))) + return false; + return isNullConversion(recv.returnType(), call.returnType()); + } + + /** + * Determine if the JVM verifier allows a value of type call to be + * passed to a formal parameter (or return variable) of type recv. + * Returns 1 if the verifier allows the types to match without conversion. + * Returns -1 if the types can be made to match by a JVM-supported adapter. + * Cases supported are: + * + * (Autoboxing is not supported here; it must be done via Java code.) + * Returns 0 otherwise. + */ + public static int canPassUnchecked(Class src, Class dst) { + if (src == dst) + return 1; + + if (dst.isPrimitive()) { + if (dst == void.class) + // Return anything to a caller expecting void. + // This is a property of the implementation, which links + // return values via a register rather than via a stack push. + // This makes it possible to ignore cleanly. + return 1; + if (src == void.class) + return 0; // void-to-something? + if (!src.isPrimitive()) + // Cannot pass a reference to any primitive type (exc. void). + return 0; + Wrapper sw = Wrapper.forPrimitiveType(src); + Wrapper dw = Wrapper.forPrimitiveType(dst); + if (sw.isSubwordOrInt() && dw.isSubwordOrInt()) { + if (sw.bitWidth() >= dw.bitWidth()) + return -1; // truncation may be required + if (!dw.isSigned() && sw.isSigned()) + return -1; // sign elimination may be required + return 1; + } + if (src == float.class || dst == float.class) { + if (src == double.class || dst == double.class) + return -1; // floating conversion may be required + else + return 0; // other primitive conversions NYI + } else { + // all fixed-point conversions are supported + return 0; + } + } else if (src.isPrimitive()) { + // Cannot pass a primitive to any reference type. + // (Maybe allow null.class?) + return 0; + } + + // Handle reference types in the rest of the block: + + // The verifier treats interfaces exactly like Object. + if (isNullReferenceConversion(src, dst)) + // pass any reference to object or an arb. interface + return 1; + // else it's a definite "maybe" (cast is required) + return -1; + } + + public static boolean isSpreadArgType(Class spreadArg) { + return spreadArg.isArray(); + } + public static Class spreadArgElementType(Class spreadArg, int i) { + return spreadArg.getComponentType(); + } +}