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 * 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).
 *
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package com.sun.tools.javac.comp;

import com.sun.tools.javac.code.*;
import com.sun.tools.javac.jvm.*;
import com.sun.tools.javac.util.*;

import static com.sun.tools.javac.code.TypeTag.BOOLEAN;

import static com.sun.tools.javac.jvm.ByteCodes.*;

Helper class for constant folding, used by the attribution phase.
 This class is marked strictfp as mandated by JLS 15.4.
 
This is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.
/** Helper class for constant folding, used by the attribution phase.
 *  This class is marked strictfp as mandated by JLS 15.4.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
strictfp class ConstFold {
    protected static final Context.Key<ConstFold> constFoldKey = new Context.Key<>();

    private Symtab syms;

    public static ConstFold instance(Context context) {
        ConstFold instance = context.get(constFoldKey);
        if (instance == null)
            instance = new ConstFold(context);
        return instance;
    }

    private ConstFold(Context context) {
        context.put(constFoldKey, this);

        syms = Symtab.instance(context);
    }

    static final Integer minusOne = -1;
    static final Integer zero     = 0;
    static final Integer one      = 1;

   
Convert boolean to integer (true = 1, false = 0).
/** Convert boolean to integer (true = 1, false = 0).
    */
    private static Integer b2i(boolean b) {
        return b ? one : zero;
    }
    private static int intValue(Object x) { return ((Number)x).intValue(); }
    private static long longValue(Object x) { return ((Number)x).longValue(); }
    private static float floatValue(Object x) { return ((Number)x).floatValue(); }
    private static double doubleValue(Object x) { return ((Number)x).doubleValue(); }

    
Fold binary or unary operation, returning constant type reflecting the
 operations result. Return null if fold failed due to an
 arithmetic exception.
 @param opcode    The operation's opcode instruction (usually a byte code),
                  as entered by class Symtab.
 @param argtypes  The operation's argument types (a list of length 1 or 2).
                  Argument types are assumed to have non-null constValue's.
/** Fold binary or unary operation, returning constant type reflecting the
     *  operations result. Return null if fold failed due to an
     *  arithmetic exception.
     *  @param opcode    The operation's opcode instruction (usually a byte code),
     *                   as entered by class Symtab.
     *  @param argtypes  The operation's argument types (a list of length 1 or 2).
     *                   Argument types are assumed to have non-null constValue's.
     */
    Type fold(int opcode, List<Type> argtypes) {
        int argCount = argtypes.length();
        if (argCount == 1)
            return fold1(opcode, argtypes.head);
        else if (argCount == 2)
            return fold2(opcode, argtypes.head, argtypes.tail.head);
        else
            throw new AssertionError();
    }

    
Fold unary operation.
 @param opcode    The operation's opcode instruction (usually a byte code),
                  as entered by class Symtab.
                  opcode's ifeq to ifge are for postprocessing
                  xcmp; ifxx pairs of instructions.
 @param operand   The operation's operand type.
                  Argument types are assumed to have non-null constValue's.
/** Fold unary operation.
     *  @param opcode    The operation's opcode instruction (usually a byte code),
     *                   as entered by class Symtab.
     *                   opcode's ifeq to ifge are for postprocessing
     *                   xcmp; ifxx pairs of instructions.
     *  @param operand   The operation's operand type.
     *                   Argument types are assumed to have non-null constValue's.
     */
    Type fold1(int opcode, Type operand) {
        try {
            Object od = operand.constValue();
            switch (opcode) {
            case nop:
                return operand;
            case ineg: // unary -
                return syms.intType.constType(-intValue(od));
            case ixor: // ~
                return syms.intType.constType(~intValue(od));
            case bool_not: // !
                return syms.booleanType.constType(b2i(intValue(od) == 0));
            case ifeq:
                return syms.booleanType.constType(b2i(intValue(od) == 0));
            case ifne:
                return syms.booleanType.constType(b2i(intValue(od) != 0));
            case iflt:
                return syms.booleanType.constType(b2i(intValue(od) < 0));
            case ifgt:
                return syms.booleanType.constType(b2i(intValue(od) > 0));
            case ifle:
                return syms.booleanType.constType(b2i(intValue(od) <= 0));
            case ifge:
                return syms.booleanType.constType(b2i(intValue(od) >= 0));

            case lneg: // unary -
                return syms.longType.constType(Long.valueOf(-longValue(od)));
            case lxor: // ~
                return syms.longType.constType(Long.valueOf(~longValue(od)));

            case fneg: // unary -
                return syms.floatType.constType(Float.valueOf(-floatValue(od)));

            case dneg: // ~
                return syms.doubleType.constType(Double.valueOf(-doubleValue(od)));

            default:
                return null;
            }
        } catch (ArithmeticException e) {
            return null;
        }
    }

    
Fold binary operation.
 @param opcode    The operation's opcode instruction (usually a byte code),
                  as entered by class Symtab.
                  opcode's ifeq to ifge are for postprocessing
                  xcmp; ifxx pairs of instructions.
 @param left      The type of the operation's left operand.
 @param right     The type of the operation's right operand.
/** Fold binary operation.
     *  @param opcode    The operation's opcode instruction (usually a byte code),
     *                   as entered by class Symtab.
     *                   opcode's ifeq to ifge are for postprocessing
     *                   xcmp; ifxx pairs of instructions.
     *  @param left      The type of the operation's left operand.
     *  @param right     The type of the operation's right operand.
     */
    Type fold2(int opcode, Type left, Type right) {
        try {
            if (opcode > ByteCodes.preMask) {
                // we are seeing a composite instruction of the form xcmp; ifxx.
                // In this case fold both instructions separately.
                Type t1 = fold2(opcode >> ByteCodes.preShift, left, right);
                return (t1.constValue() == null) ? t1
                    : fold1(opcode & ByteCodes.preMask, t1);
            } else {
                Object l = left.constValue();
                Object r = right.constValue();
                switch (opcode) {
                case iadd:
                    return syms.intType.constType(intValue(l) + intValue(r));
                case isub:
                    return syms.intType.constType(intValue(l) - intValue(r));
                case imul:
                    return syms.intType.constType(intValue(l) * intValue(r));
                case idiv:
                    return syms.intType.constType(intValue(l) / intValue(r));
                case imod:
                    return syms.intType.constType(intValue(l) % intValue(r));
                case iand:
                    return (left.hasTag(BOOLEAN)
                      ? syms.booleanType : syms.intType)
                      .constType(intValue(l) & intValue(r));
                case bool_and:
                    return syms.booleanType.constType(b2i((intValue(l) & intValue(r)) != 0));
                case ior:
                    return (left.hasTag(BOOLEAN)
                      ? syms.booleanType : syms.intType)
                      .constType(intValue(l) | intValue(r));
                case bool_or:
                    return syms.booleanType.constType(b2i((intValue(l) | intValue(r)) != 0));
                case ixor:
                    return (left.hasTag(BOOLEAN)
                      ? syms.booleanType : syms.intType)
                      .constType(intValue(l) ^ intValue(r));
                case ishl: case ishll:
                    return syms.intType.constType(intValue(l) << intValue(r));
                case ishr: case ishrl:
                    return syms.intType.constType(intValue(l) >> intValue(r));
                case iushr: case iushrl:
                    return syms.intType.constType(intValue(l) >>> intValue(r));
                case if_icmpeq:
                    return syms.booleanType.constType(
                        b2i(intValue(l) == intValue(r)));
                case if_icmpne:
                    return syms.booleanType.constType(
                        b2i(intValue(l) != intValue(r)));
                case if_icmplt:
                    return syms.booleanType.constType(
                        b2i(intValue(l) < intValue(r)));
                case if_icmpgt:
                    return syms.booleanType.constType(
                        b2i(intValue(l) > intValue(r)));
                case if_icmple:
                    return syms.booleanType.constType(
                        b2i(intValue(l) <= intValue(r)));
                case if_icmpge:
                    return syms.booleanType.constType(
                        b2i(intValue(l) >= intValue(r)));

                case ladd:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) + longValue(r)));
                case lsub:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) - longValue(r)));
                case lmul:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) * longValue(r)));
                case ldiv:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) / longValue(r)));
                case lmod:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) % longValue(r)));
                case land:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) & longValue(r)));
                case lor:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) | longValue(r)));
                case lxor:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) ^ longValue(r)));
                case lshl: case lshll:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) << intValue(r)));
                case lshr: case lshrl:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) >> intValue(r)));
                case lushr:
                    return syms.longType.constType(
                        Long.valueOf(longValue(l) >>> intValue(r)));
                case lcmp:
                    if (longValue(l) < longValue(r))
                        return syms.intType.constType(minusOne);
                    else if (longValue(l) > longValue(r))
                        return syms.intType.constType(one);
                    else
                        return syms.intType.constType(zero);
                case fadd:
                    return syms.floatType.constType(
                        Float.valueOf(floatValue(l) + floatValue(r)));
                case fsub:
                    return syms.floatType.constType(
                        Float.valueOf(floatValue(l) - floatValue(r)));
                case fmul:
                    return syms.floatType.constType(
                        Float.valueOf(floatValue(l) * floatValue(r)));
                case fdiv:
                    return syms.floatType.constType(
                        Float.valueOf(floatValue(l) / floatValue(r)));
                case fmod:
                    return syms.floatType.constType(
                        Float.valueOf(floatValue(l) % floatValue(r)));
                case fcmpg: case fcmpl:
                    if (floatValue(l) < floatValue(r))
                        return syms.intType.constType(minusOne);
                    else if (floatValue(l) > floatValue(r))
                        return syms.intType.constType(one);
                    else if (floatValue(l) == floatValue(r))
                        return syms.intType.constType(zero);
                    else if (opcode == fcmpg)
                        return syms.intType.constType(one);
                    else
                        return syms.intType.constType(minusOne);
                case dadd:
                    return syms.doubleType.constType(
                        Double.valueOf(doubleValue(l) + doubleValue(r)));
                case dsub:
                    return syms.doubleType.constType(
                        Double.valueOf(doubleValue(l) - doubleValue(r)));
                case dmul:
                    return syms.doubleType.constType(
                        Double.valueOf(doubleValue(l) * doubleValue(r)));
                case ddiv:
                    return syms.doubleType.constType(
                        Double.valueOf(doubleValue(l) / doubleValue(r)));
                case dmod:
                    return syms.doubleType.constType(
                        Double.valueOf(doubleValue(l) % doubleValue(r)));
                case dcmpg: case dcmpl:
                    if (doubleValue(l) < doubleValue(r))
                        return syms.intType.constType(minusOne);
                    else if (doubleValue(l) > doubleValue(r))
                        return syms.intType.constType(one);
                    else if (doubleValue(l) == doubleValue(r))
                        return syms.intType.constType(zero);
                    else if (opcode == dcmpg)
                        return syms.intType.constType(one);
                    else
                        return syms.intType.constType(minusOne);
                case if_acmpeq:
                    return syms.booleanType.constType(b2i(l.equals(r)));
                case if_acmpne:
                    return syms.booleanType.constType(b2i(!l.equals(r)));
                case string_add:
                    return syms.stringType.constType(
                        left.stringValue() + right.stringValue());
                default:
                    return null;
                }
            }
        } catch (ArithmeticException e) {
            return null;
        }
    }

    
Coerce constant type to target type.
 @param etype      The source type of the coercion,
                   which is assumed to be a constant type compatible with
                   ttype.
 @param ttype      The target type of the coercion.
/** Coerce constant type to target type.
     *  @param etype      The source type of the coercion,
     *                    which is assumed to be a constant type compatible with
     *                    ttype.
     *  @param ttype      The target type of the coercion.
     */
     Type coerce(Type etype, Type ttype) {
         // WAS if (etype.baseType() == ttype.baseType())
         if (etype.tsym.type == ttype.tsym.type)
             return etype;
         if (etype.isNumeric()) {
             Object n = etype.constValue();
             switch (ttype.getTag()) {
             case BYTE:
                 return syms.byteType.constType(0 + (byte)intValue(n));
             case CHAR:
                 return syms.charType.constType(0 + (char)intValue(n));
             case SHORT:
                 return syms.shortType.constType(0 + (short)intValue(n));
             case INT:
                 return syms.intType.constType(intValue(n));
             case LONG:
                 return syms.longType.constType(longValue(n));
             case FLOAT:
                 return syms.floatType.constType(floatValue(n));
             case DOUBLE:
                 return syms.doubleType.constType(doubleValue(n));
             }
         }
         return ttype;
     }
}