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com.sun.tools.javac.comp
class: ConstFold [javadoc | source]

java.lang.Object
   com.sun.tools.javac.comp.ConstFold

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.

Field Summary
protected static final  Key<ConstFold>	constFoldKey
static  Integer	minusOne
static  Integer	zero
static  Integer	one

Method from com.sun.tools.javac.comp.ConstFold Summary:
coerce,   fold,   fold1,   fold2,   instance

Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait

Method from com.sun.tools.javac.comp.ConstFold Detail:
Type coerce(Type etype, Type ttype) { // WAS if (etype.baseType() == ttype.baseType()) if (etype.tsym.type == ttype.tsym.type) return etype; if (etype.tag < = DOUBLE) { Object n = etype.constValue(); switch (ttype.tag) { 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; } Coerce constant type to target type.
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 binary or unary operation, returning constant type reflecting the operations result. Return null if fold failed due to an arithmetic exception.
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 unary operation.
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.tag == 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.tag == 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.tag == 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; } } Fold binary operation.
public static ConstFold instance(Context context) { ConstFold instance = context.get(constFoldKey); if (instance == null) instance = new ConstFold(context); return instance; }