1 /*
   2  * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.tools.javac.comp;
  27 
  28 import com.sun.tools.javac.code.*;
  29 import com.sun.tools.javac.jvm.*;
  30 import com.sun.tools.javac.util.*;
  31 
  32 import static com.sun.tools.javac.code.TypeTag.BOOLEAN;
  33 
  34 import static com.sun.tools.javac.jvm.ByteCodes.*;
  35 
  36 /** Helper class for constant folding, used by the attribution phase.
  37  *  This class is marked strictfp as mandated by JLS 15.4.
  38  *
  39  *  <p><b>This is NOT part of any supported API.
  40  *  If you write code that depends on this, you do so at your own risk.
  41  *  This code and its internal interfaces are subject to change or
  42  *  deletion without notice.</b>
  43  */
  44 strictfp class ConstFold {
  45     protected static final Context.Key<ConstFold> constFoldKey = new Context.Key<>();
  46 
  47     private Symtab syms;
  48 
  49     public static ConstFold instance(Context context) {
  50         ConstFold instance = context.get(constFoldKey);
  51         if (instance == null)
  52             instance = new ConstFold(context);
  53         return instance;
  54     }
  55 
  56     private ConstFold(Context context) {
  57         context.put(constFoldKey, this);
  58 
  59         syms = Symtab.instance(context);
  60     }
  61 
  62     static final Integer minusOne = -1;
  63     static final Integer zero     = 0;
  64     static final Integer one      = 1;
  65 
  66    /** Convert boolean to integer (true = 1, false = 0).
  67     */
  68     private static Integer b2i(boolean b) {
  69         return b ? one : zero;
  70     }
  71     private static int intValue(Object x) { return ((Number)x).intValue(); }
  72     private static long longValue(Object x) { return ((Number)x).longValue(); }
  73     private static float floatValue(Object x) { return ((Number)x).floatValue(); }
  74     private static double doubleValue(Object x) { return ((Number)x).doubleValue(); }
  75 
  76     /** Fold unary operation.
  77      *  @param opcode    The operation's opcode instruction (usually a byte code),
  78      *                   as entered by class Symtab.
  79      *                   opcode's ifeq to ifge are for postprocessing
  80      *                   xcmp; ifxx pairs of instructions.
  81      *  @param operand   The operation's operand type.
  82      *                   Argument types are assumed to have non-null constValue's.
  83      */
  84     Type fold1(int opcode, Type operand) {
  85         try {
  86             Object od = operand.constValue();
  87             switch (opcode) {
  88             case nop:
  89                 return operand;
  90             case ineg: // unary -
  91                 return syms.intType.constType(-intValue(od));
  92             case ixor: // ~
  93                 return syms.intType.constType(~intValue(od));
  94             case bool_not: // !
  95                 return syms.booleanType.constType(b2i(intValue(od) == 0));
  96             case ifeq:
  97                 return syms.booleanType.constType(b2i(intValue(od) == 0));
  98             case ifne:
  99                 return syms.booleanType.constType(b2i(intValue(od) != 0));
 100             case iflt:
 101                 return syms.booleanType.constType(b2i(intValue(od) < 0));
 102             case ifgt:
 103                 return syms.booleanType.constType(b2i(intValue(od) > 0));
 104             case ifle:
 105                 return syms.booleanType.constType(b2i(intValue(od) <= 0));
 106             case ifge:
 107                 return syms.booleanType.constType(b2i(intValue(od) >= 0));
 108 
 109             case lneg: // unary -
 110                 return syms.longType.constType(Long.valueOf(-longValue(od)));
 111             case lxor: // ~
 112                 return syms.longType.constType(Long.valueOf(~longValue(od)));
 113 
 114             case fneg: // unary -
 115                 return syms.floatType.constType(Float.valueOf(-floatValue(od)));
 116 
 117             case dneg: // ~
 118                 return syms.doubleType.constType(Double.valueOf(-doubleValue(od)));
 119 
 120             default:
 121                 return null;
 122             }
 123         } catch (ArithmeticException e) {
 124             return null;
 125         }
 126     }
 127 
 128     /** Fold binary operation.
 129      *  @param opcode    The operation's opcode instruction (usually a byte code),
 130      *                   as entered by class Symtab.
 131      *                   opcode's ifeq to ifge are for postprocessing
 132      *                   xcmp; ifxx pairs of instructions.
 133      *  @param left      The type of the operation's left operand.
 134      *  @param right     The type of the operation's right operand.
 135      */
 136     Type fold2(int opcode, Type left, Type right) {
 137         try {
 138             if (opcode > ByteCodes.preMask) {
 139                 // we are seeing a composite instruction of the form xcmp; ifxx.
 140                 // In this case fold both instructions separately.
 141                 Type t1 = fold2(opcode >> ByteCodes.preShift, left, right);
 142                 return (t1.constValue() == null) ? t1
 143                     : fold1(opcode & ByteCodes.preMask, t1);
 144             } else {
 145                 Object l = left.constValue();
 146                 Object r = right.constValue();
 147                 switch (opcode) {
 148                 case iadd:
 149                     return syms.intType.constType(intValue(l) + intValue(r));
 150                 case isub:
 151                     return syms.intType.constType(intValue(l) - intValue(r));
 152                 case imul:
 153                     return syms.intType.constType(intValue(l) * intValue(r));
 154                 case idiv:
 155                     return syms.intType.constType(intValue(l) / intValue(r));
 156                 case imod:
 157                     return syms.intType.constType(intValue(l) % intValue(r));
 158                 case iand:
 159                     return (left.hasTag(BOOLEAN)
 160                       ? syms.booleanType : syms.intType)
 161                       .constType(intValue(l) & intValue(r));
 162                 case bool_and:
 163                     return syms.booleanType.constType(b2i((intValue(l) & intValue(r)) != 0));
 164                 case ior:
 165                     return (left.hasTag(BOOLEAN)
 166                       ? syms.booleanType : syms.intType)
 167                       .constType(intValue(l) | intValue(r));
 168                 case bool_or:
 169                     return syms.booleanType.constType(b2i((intValue(l) | intValue(r)) != 0));
 170                 case ixor:
 171                     return (left.hasTag(BOOLEAN)
 172                       ? syms.booleanType : syms.intType)
 173                       .constType(intValue(l) ^ intValue(r));
 174                 case ishl: case ishll:
 175                     return syms.intType.constType(intValue(l) << intValue(r));
 176                 case ishr: case ishrl:
 177                     return syms.intType.constType(intValue(l) >> intValue(r));
 178                 case iushr: case iushrl:
 179                     return syms.intType.constType(intValue(l) >>> intValue(r));
 180                 case if_icmpeq:
 181                     return syms.booleanType.constType(
 182                         b2i(intValue(l) == intValue(r)));
 183                 case if_icmpne:
 184                     return syms.booleanType.constType(
 185                         b2i(intValue(l) != intValue(r)));
 186                 case if_icmplt:
 187                     return syms.booleanType.constType(
 188                         b2i(intValue(l) < intValue(r)));
 189                 case if_icmpgt:
 190                     return syms.booleanType.constType(
 191                         b2i(intValue(l) > intValue(r)));
 192                 case if_icmple:
 193                     return syms.booleanType.constType(
 194                         b2i(intValue(l) <= intValue(r)));
 195                 case if_icmpge:
 196                     return syms.booleanType.constType(
 197                         b2i(intValue(l) >= intValue(r)));
 198 
 199                 case ladd:
 200                     return syms.longType.constType(
 201                         Long.valueOf(longValue(l) + longValue(r)));
 202                 case lsub:
 203                     return syms.longType.constType(
 204                         Long.valueOf(longValue(l) - longValue(r)));
 205                 case lmul:
 206                     return syms.longType.constType(
 207                         Long.valueOf(longValue(l) * longValue(r)));
 208                 case ldiv:
 209                     return syms.longType.constType(
 210                         Long.valueOf(longValue(l) / longValue(r)));
 211                 case lmod:
 212                     return syms.longType.constType(
 213                         Long.valueOf(longValue(l) % longValue(r)));
 214                 case land:
 215                     return syms.longType.constType(
 216                         Long.valueOf(longValue(l) & longValue(r)));
 217                 case lor:
 218                     return syms.longType.constType(
 219                         Long.valueOf(longValue(l) | longValue(r)));
 220                 case lxor:
 221                     return syms.longType.constType(
 222                         Long.valueOf(longValue(l) ^ longValue(r)));
 223                 case lshl: case lshll:
 224                     return syms.longType.constType(
 225                         Long.valueOf(longValue(l) << intValue(r)));
 226                 case lshr: case lshrl:
 227                     return syms.longType.constType(
 228                         Long.valueOf(longValue(l) >> intValue(r)));
 229                 case lushr:
 230                     return syms.longType.constType(
 231                         Long.valueOf(longValue(l) >>> intValue(r)));
 232                 case lcmp:
 233                     if (longValue(l) < longValue(r))
 234                         return syms.intType.constType(minusOne);
 235                     else if (longValue(l) > longValue(r))
 236                         return syms.intType.constType(one);
 237                     else
 238                         return syms.intType.constType(zero);
 239                 case fadd:
 240                     return syms.floatType.constType(
 241                         Float.valueOf(floatValue(l) + floatValue(r)));
 242                 case fsub:
 243                     return syms.floatType.constType(
 244                         Float.valueOf(floatValue(l) - floatValue(r)));
 245                 case fmul:
 246                     return syms.floatType.constType(
 247                         Float.valueOf(floatValue(l) * floatValue(r)));
 248                 case fdiv:
 249                     return syms.floatType.constType(
 250                         Float.valueOf(floatValue(l) / floatValue(r)));
 251                 case fmod:
 252                     return syms.floatType.constType(
 253                         Float.valueOf(floatValue(l) % floatValue(r)));
 254                 case fcmpg: case fcmpl:
 255                     if (floatValue(l) < floatValue(r))
 256                         return syms.intType.constType(minusOne);
 257                     else if (floatValue(l) > floatValue(r))
 258                         return syms.intType.constType(one);
 259                     else if (floatValue(l) == floatValue(r))
 260                         return syms.intType.constType(zero);
 261                     else if (opcode == fcmpg)
 262                         return syms.intType.constType(one);
 263                     else
 264                         return syms.intType.constType(minusOne);
 265                 case dadd:
 266                     return syms.doubleType.constType(
 267                         Double.valueOf(doubleValue(l) + doubleValue(r)));
 268                 case dsub:
 269                     return syms.doubleType.constType(
 270                         Double.valueOf(doubleValue(l) - doubleValue(r)));
 271                 case dmul:
 272                     return syms.doubleType.constType(
 273                         Double.valueOf(doubleValue(l) * doubleValue(r)));
 274                 case ddiv:
 275                     return syms.doubleType.constType(
 276                         Double.valueOf(doubleValue(l) / doubleValue(r)));
 277                 case dmod:
 278                     return syms.doubleType.constType(
 279                         Double.valueOf(doubleValue(l) % doubleValue(r)));
 280                 case dcmpg: case dcmpl:
 281                     if (doubleValue(l) < doubleValue(r))
 282                         return syms.intType.constType(minusOne);
 283                     else if (doubleValue(l) > doubleValue(r))
 284                         return syms.intType.constType(one);
 285                     else if (doubleValue(l) == doubleValue(r))
 286                         return syms.intType.constType(zero);
 287                     else if (opcode == dcmpg)
 288                         return syms.intType.constType(one);
 289                     else
 290                         return syms.intType.constType(minusOne);
 291                 case if_acmpeq:
 292                     return syms.booleanType.constType(b2i(l.equals(r)));
 293                 case if_acmpne:
 294                     return syms.booleanType.constType(b2i(!l.equals(r)));
 295                 case string_add:
 296                     return syms.stringType.constType(
 297                         left.stringValue() + right.stringValue());
 298                 default:
 299                     return null;
 300                 }
 301             }
 302         } catch (ArithmeticException e) {
 303             return null;
 304         }
 305     }
 306 
 307     /** Coerce constant type to target type.
 308      *  @param etype      The source type of the coercion,
 309      *                    which is assumed to be a constant type compatible with
 310      *                    ttype.
 311      *  @param ttype      The target type of the coercion.
 312      */
 313      Type coerce(Type etype, Type ttype) {
 314          // WAS if (etype.baseType() == ttype.baseType())
 315          if (etype.tsym.type == ttype.tsym.type)
 316              return etype;
 317          if (etype.isNumeric()) {
 318              Object n = etype.constValue();
 319              switch (ttype.getTag()) {
 320              case BYTE:
 321                  return syms.byteType.constType(0 + (byte)intValue(n));
 322              case CHAR:
 323                  return syms.charType.constType(0 + (char)intValue(n));
 324              case SHORT:
 325                  return syms.shortType.constType(0 + (short)intValue(n));
 326              case INT:
 327                  return syms.intType.constType(intValue(n));
 328              case LONG:
 329                  return syms.longType.constType(longValue(n));
 330              case FLOAT:
 331                  return syms.floatType.constType(floatValue(n));
 332              case DOUBLE:
 333                  return syms.doubleType.constType(doubleValue(n));
 334              }
 335          }
 336          return ttype;
 337      }
 338 }