Java example source code file (ConstFold.java)
The ConstFold.java Java example source code
/*
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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).
*
* 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.
*
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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.
*
* <p>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<ConstFold>();
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).
*/
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.
*/
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.
*/
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(new Long(-longValue(od)));
case lxor: // ~
return syms.longType.constType(new Long(~longValue(od)));
case fneg: // unary -
return syms.floatType.constType(new Float(-floatValue(od)));
case dneg: // ~
return syms.doubleType.constType(new Double(-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.
*/
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(
new Long(longValue(l) + longValue(r)));
case lsub:
return syms.longType.constType(
new Long(longValue(l) - longValue(r)));
case lmul:
return syms.longType.constType(
new Long(longValue(l) * longValue(r)));
case ldiv:
return syms.longType.constType(
new Long(longValue(l) / longValue(r)));
case lmod:
return syms.longType.constType(
new Long(longValue(l) % longValue(r)));
case land:
return syms.longType.constType(
new Long(longValue(l) & longValue(r)));
case lor:
return syms.longType.constType(
new Long(longValue(l) | longValue(r)));
case lxor:
return syms.longType.constType(
new Long(longValue(l) ^ longValue(r)));
case lshl: case lshll:
return syms.longType.constType(
new Long(longValue(l) << intValue(r)));
case lshr: case lshrl:
return syms.longType.constType(
new Long(longValue(l) >> intValue(r)));
case lushr:
return syms.longType.constType(
new Long(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(
new Float(floatValue(l) + floatValue(r)));
case fsub:
return syms.floatType.constType(
new Float(floatValue(l) - floatValue(r)));
case fmul:
return syms.floatType.constType(
new Float(floatValue(l) * floatValue(r)));
case fdiv:
return syms.floatType.constType(
new Float(floatValue(l) / floatValue(r)));
case fmod:
return syms.floatType.constType(
new Float(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(
new Double(doubleValue(l) + doubleValue(r)));
case dsub:
return syms.doubleType.constType(
new Double(doubleValue(l) - doubleValue(r)));
case dmul:
return syms.doubleType.constType(
new Double(doubleValue(l) * doubleValue(r)));
case ddiv:
return syms.doubleType.constType(
new Double(doubleValue(l) / doubleValue(r)));
case dmod:
return syms.doubleType.constType(
new Double(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.
*/
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;
}
}
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