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/* ************************************************************************
* Pizza constant folder
* by Martin Odersky
*
* Copyright (C) 1996,97 Martin Odersky. All rights reserved.
* Permission is hereby granted to modify and use this software for research
* and teaching purposes. Modification for commercial purposes requires
* prior written permission by the author.
* The software, or modifications thereof, may be redistributed only
* if this copyright notice stays attached.
*************************************************************************/
package scalac.typechecker;
import scalac.Global;
import scalac.ast.Tree;
import scalac.ast.TreeGen;
import scalac.atree.AConstant;
import scalac.atree.ATypeKind;
import scalac.symtab.Definitions;
import scalac.symtab.Type;
import scalac.util.Name;
import scalac.util.Names;
public class ConstantFolder {
//########################################################################
// Private Fields
/** The global definitions */
private final Definitions definitions;
/** The tree generator */
private final TreeGen gen;
//########################################################################
// Public Constructors
/** Initializes this instance. */
public ConstantFolder(Global global) {
this.definitions = global.definitions;
this.gen = global.treeGen;
}
//########################################################################
// Public Methods
/**
* Attempts to constant fold given tree. Returns the input tree if
* constant folding fails.
*/
public Tree tryToFold(Tree tree) {
AConstant value = evaluate(tree);
return value != null ? gen.Literal(tree.pos, value) : tree;
}
/**
* Evaluates the expression represented by the tree and returns
* the resulting value. Returns null if the evaluation can't be
* performed.
*/
public AConstant evaluate(Tree tree) {
switch (tree) {
case TypeApply(Select(Tree qualifier, Name op), Tree[] args):
switch (qualifier.type()) {
case ConstantType(_, AConstant lvalue):
if (args.length == 1 && op == Names.asInstanceOf)
return cast(lvalue, args[0].type());
return null;
default:
return null;
}
case Apply(Select(Tree qualifier, Name op), Tree[] args):
switch (qualifier.type()) {
case ConstantType(_, AConstant lvalue):
switch (args.length) {
case 0:
return evaluate(op, lvalue);
case 1:
switch (args[0].type()) {
case ConstantType(_, AConstant rvalue):
return evaluate(op, lvalue, rvalue);
default:
return null;
}
default:
return null;
}
default:
return null;
}
default:
return null;
}
}
/**
* Evaluates the unary operation and returns the resulting value.
* Returns null if the evaluation can't be performed.
*/
public AConstant evaluate(Name op, AConstant value) {
switch (kind(value)) {
case ATypeKind.BOOL:
boolean v = value.booleanValue();
if (op == Names.ZNOT) return AConstant.BOOLEAN(!v);
return null;
case ATypeKind.I4:
int v = value.intValue();
if (op == Names.ADD) return AConstant.INT(+v);
if (op == Names.SUB) return AConstant.INT(-v);
if (op == Names.NOT) return AConstant.INT(~v);
return null;
case ATypeKind.I8:
long v = value.longValue();
if (op == Names.ADD) return AConstant.LONG(+v);
if (op == Names.SUB) return AConstant.LONG(-v);
if (op == Names.NOT) return AConstant.LONG(~v);
return null;
case ATypeKind.R4:
float v = value.floatValue();
if (op == Names.ADD) return AConstant.FLOAT(+v);
if (op == Names.SUB) return AConstant.FLOAT(-v);
return null;
case ATypeKind.R8:
double v = value.doubleValue();
if (op == Names.ADD) return AConstant.DOUBLE(+v);
if (op == Names.SUB) return AConstant.DOUBLE(-v);
return null;
default:
return null;
}
}
/**
* Evaluates the binary operation and returns the resulting value.
* Returns null if the evaluation can't be performed.
*/
public AConstant evaluate(Name op, AConstant lvalue, AConstant rvalue) {
ATypeKind kind = kind(lvalue, rvalue);
if (kind == null) return null;
switch (kind) {
case ATypeKind.I4:
int l = lvalue.intValue();
int r = rvalue.intValue();
if (op == Names.OR ) return AConstant.INT(l | r);
if (op == Names.AND) return AConstant.INT(l & r);
if (op == Names.XOR) return AConstant.INT(l ^ r);
if (op == Names.ADD) return AConstant.INT(l + r);
if (op == Names.SUB) return AConstant.INT(l - r);
if (op == Names.MUL) return AConstant.INT(l * r);
if (op == Names.DIV) return r == 0 ? null : AConstant.INT(l / r);
if (op == Names.MOD) return r == 0 ? null : AConstant.INT(l % r);
if (op == Names.EQ ) return AConstant.BOOLEAN(l == r);
if (op == Names.NE ) return AConstant.BOOLEAN(l != r);
if (op == Names.LT ) return AConstant.BOOLEAN(l < r);
if (op == Names.GT ) return AConstant.BOOLEAN(l > r);
if (op == Names.LE ) return AConstant.BOOLEAN(l <= r);
if (op == Names.GE ) return AConstant.BOOLEAN(l >= r);
if (op == Names.LSL) return AConstant.INT(l << r);
if (op == Names.LSR) return AConstant.INT(l >>> r);
if (op == Names.ASR) return AConstant.INT(l >> r);
return null;
case ATypeKind.I8:
long l = lvalue.longValue();
long r = rvalue.longValue();
if (op == Names.OR ) return AConstant.LONG(l | r);
if (op == Names.AND) return AConstant.LONG(l & r);
if (op == Names.XOR) return AConstant.LONG(l ^ r);
if (op == Names.ADD) return AConstant.LONG(l + r);
if (op == Names.SUB) return AConstant.LONG(l - r);
if (op == Names.MUL) return AConstant.LONG(l * r);
if (op == Names.DIV) return r == 0 ? null : AConstant.LONG(l / r);
if (op == Names.MOD) return r == 0 ? null : AConstant.LONG(l % r);
if (op == Names.EQ ) return AConstant.BOOLEAN(l == r);
if (op == Names.NE ) return AConstant.BOOLEAN(l != r);
if (op == Names.LT ) return AConstant.BOOLEAN(l < r);
if (op == Names.GT ) return AConstant.BOOLEAN(l > r);
if (op == Names.LE ) return AConstant.BOOLEAN(l <= r);
if (op == Names.GE ) return AConstant.BOOLEAN(l >= r);
if (kind(lvalue) == ATypeKind.I4) {
int li = lvalue.intValue();
if (op == Names.LSL) return AConstant.INT(li << r);
if (op == Names.LSR) return AConstant.INT(li >>> r);
if (op == Names.ASR) return AConstant.INT(li >> r);
} else {
if (op == Names.LSL) return AConstant.LONG(l << r);
if (op == Names.LSR) return AConstant.LONG(l >>> r);
if (op == Names.ASR) return AConstant.LONG(l >> r);
}
return null;
case ATypeKind.R4:
float l = lvalue.floatValue();
float r = rvalue.floatValue();
if (op == Names.ADD) return AConstant.FLOAT(l + r);
if (op == Names.SUB) return AConstant.FLOAT(l - r);
if (op == Names.MUL) return AConstant.FLOAT(l * r);
if (op == Names.DIV) return AConstant.FLOAT(l / r);
if (op == Names.MOD) return AConstant.FLOAT(l % r);
if (op == Names.EQ ) return AConstant.BOOLEAN(l == r);
if (op == Names.NE ) return AConstant.BOOLEAN(l != r);
if (op == Names.LT ) return AConstant.BOOLEAN(l < r);
if (op == Names.GT ) return AConstant.BOOLEAN(l > r);
if (op == Names.LE ) return AConstant.BOOLEAN(l <= r);
if (op == Names.GE ) return AConstant.BOOLEAN(l >= r);
return null;
case ATypeKind.R8:
double l = lvalue.doubleValue();
double r = rvalue.doubleValue();
if (op == Names.ADD) return AConstant.DOUBLE(l + r);
if (op == Names.SUB) return AConstant.DOUBLE(l - r);
if (op == Names.MUL) return AConstant.DOUBLE(l * r);
if (op == Names.DIV) return AConstant.DOUBLE(l / r);
if (op == Names.MOD) return AConstant.DOUBLE(l % r);
if (op == Names.EQ ) return AConstant.BOOLEAN(l == r);
if (op == Names.NE ) return AConstant.BOOLEAN(l != r);
if (op == Names.LT ) return AConstant.BOOLEAN(l < r);
if (op == Names.GT ) return AConstant.BOOLEAN(l > r);
if (op == Names.LE ) return AConstant.BOOLEAN(l <= r);
if (op == Names.GE ) return AConstant.BOOLEAN(l >= r);
return null;
case ATypeKind.BOOL:
boolean l = lvalue.booleanValue();
boolean r = rvalue.booleanValue();
if (op == Names.ZOR ) return AConstant.BOOLEAN(l | r);
if (op == Names.OR ) return AConstant.BOOLEAN(l | r);
if (op == Names.ZAND) return AConstant.BOOLEAN(l & r);
if (op == Names.AND ) return AConstant.BOOLEAN(l & r);
if (op == Names.XOR ) return AConstant.BOOLEAN(l ^ r);
if (op == Names.EQ ) return AConstant.BOOLEAN(l == r);
if (op == Names.NE ) return AConstant.BOOLEAN(l != r);
return null;
case ATypeKind.STR:
if (op == Names.ADD)
return AConstant.STRING(lvalue.stringValue()+rvalue.stringValue());
return null;
default:
return null;
}
}
/**
* Casts the value to given type and returns the resulting value.
* Returns null if the cast can't be performed.
*/
public AConstant cast(AConstant value, Type type) {
switch (value.kind()) {
case UNIT:
if (type.isSameAs(definitions.void_TYPE())) // !!! -> UNIT_TYPE()
return value;
return null;
case BOOL:
if (type.isSameAs(definitions.boolean_TYPE()))
return value;
return null;
case U1:
case U2:
case U4:
case U8:
case I1:
case I2:
case I4:
case I8:
case R4:
case R8:
if (type.isSameAs(definitions.byte_TYPE()))
return AConstant.BYTE(value.byteValue());
if (type.isSameAs(definitions.short_TYPE()))
return AConstant.SHORT(value.shortValue());
if (type.isSameAs(definitions.char_TYPE()))
return AConstant.CHAR(value.charValue());
if (type.isSameAs(definitions.int_TYPE()))
return AConstant.INT(value.intValue());
if (type.isSameAs(definitions.long_TYPE()))
return AConstant.LONG(value.longValue());
if (type.isSameAs(definitions.float_TYPE()))
return AConstant.FLOAT(value.floatValue());
if (type.isSameAs(definitions.double_TYPE()))
return AConstant.DOUBLE(value.doubleValue());
return null;
case STR:
if (type.isSameAs(definitions.STRING_TYPE()))
return value;
return null;
default:
return null;
}
}
//########################################################################
// Private Methods
/** Returns the kind of given value. */
private ATypeKind kind(AConstant value) {
ATypeKind kind = value.kind();
switch (kind) {
case I1:
case I2:
case U2:
return ATypeKind.I4;
default:
return kind;
}
}
/**
* Returns the combined kind of given values or null if the values
* can't be combined.
*/
private ATypeKind kind(AConstant lvalue, AConstant rvalue) {
ATypeKind lkind = kind(lvalue);
ATypeKind rkind = kind(rvalue);
if (lkind == rkind) return lkind;
if (lkind == ATypeKind.ZERO) return null;
if (rkind == ATypeKind.ZERO) return null;
if (lkind == ATypeKind.STR) return lkind;
if (rkind == ATypeKind.STR) return rkind;
switch (lkind) {
case I4:
switch (rkind) {
case I4: return lkind;
case I8: return rkind;
case R4: return rkind;
case R8: return rkind;
default: return null;
}
case I8:
switch (rkind) {
case I4: return lkind;
case I8: return lkind;
case R4: return rkind;
case R8: return rkind;
default: return null;
}
case R4:
switch (rkind) {
case I4: return lkind;
case I8: return lkind;
case R4: return lkind;
case R8: return rkind;
default: return null;
}
case R8:
switch (rkind) {
case I4: return lkind;
case I8: return lkind;
case R4: return lkind;
case R8: return lkind;
default: return null;
}
default:
return null;
}
}
//########################################################################
}
|
