Java example source code file (Items.java)
The Items.java Java example source code
/*
* Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
* 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.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.tools.javac.jvm;
import com.sun.tools.javac.code.*;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.code.Type.*;
import com.sun.tools.javac.jvm.Code.*;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.util.Assert;
import static com.sun.tools.javac.jvm.ByteCodes.*;
/** A helper class for code generation. Items are objects
* that stand for addressable entities in the bytecode. Each item
* supports a fixed protocol for loading the item on the stack, storing
* into it, converting it into a jump condition, and several others.
* There are many individual forms of items, such as local, static,
* indexed, or instance variables, values on the top of stack, the
* special values this or super, etc. Individual items are represented as
* inner classes in class Items.
*
* <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>
*/
public class Items {
/** The current constant pool.
*/
Pool pool;
/** The current code buffer.
*/
Code code;
/** The current symbol table.
*/
Symtab syms;
/** Type utilities. */
Types types;
/** Items that exist only once (flyweight pattern).
*/
private final Item voidItem;
private final Item thisItem;
private final Item superItem;
private final Item[] stackItem = new Item[TypeCodeCount];
public Items(Pool pool, Code code, Symtab syms, Types types) {
this.code = code;
this.pool = pool;
this.types = types;
voidItem = new Item(VOIDcode) {
public String toString() { return "void"; }
};
thisItem = new SelfItem(false);
superItem = new SelfItem(true);
for (int i = 0; i < VOIDcode; i++) stackItem[i] = new StackItem(i);
stackItem[VOIDcode] = voidItem;
this.syms = syms;
}
/** Make a void item
*/
Item makeVoidItem() {
return voidItem;
}
/** Make an item representing `this'.
*/
Item makeThisItem() {
return thisItem;
}
/** Make an item representing `super'.
*/
Item makeSuperItem() {
return superItem;
}
/** Make an item representing a value on stack.
* @param type The value's type.
*/
Item makeStackItem(Type type) {
return stackItem[Code.typecode(type)];
}
/** Make an item representing a dynamically invoked method.
* @param member The represented symbol.
*/
Item makeDynamicItem(Symbol member) {
return new DynamicItem(member);
}
/** Make an item representing an indexed expression.
* @param type The expression's type.
*/
Item makeIndexedItem(Type type) {
return new IndexedItem(type);
}
/** Make an item representing a local variable.
* @param v The represented variable.
*/
LocalItem makeLocalItem(VarSymbol v) {
return new LocalItem(v.erasure(types), v.adr);
}
/** Make an item representing a local anonymous variable.
* @param type The represented variable's type.
* @param reg The represented variable's register.
*/
private LocalItem makeLocalItem(Type type, int reg) {
return new LocalItem(type, reg);
}
/** Make an item representing a static variable or method.
* @param member The represented symbol.
*/
Item makeStaticItem(Symbol member) {
return new StaticItem(member);
}
/** Make an item representing an instance variable or method.
* @param member The represented symbol.
* @param nonvirtual Is the reference not virtual? (true for constructors
* and private members).
*/
Item makeMemberItem(Symbol member, boolean nonvirtual) {
return new MemberItem(member, nonvirtual);
}
/** Make an item representing a literal.
* @param type The literal's type.
* @param value The literal's value.
*/
Item makeImmediateItem(Type type, Object value) {
return new ImmediateItem(type, value);
}
/** Make an item representing an assignment expression.
* @param lhs The item representing the assignment's left hand side.
*/
Item makeAssignItem(Item lhs) {
return new AssignItem(lhs);
}
/** Make an item representing a conditional or unconditional jump.
* @param opcode The jump's opcode.
* @param trueJumps A chain encomassing all jumps that can be taken
* if the condition evaluates to true.
* @param falseJumps A chain encomassing all jumps that can be taken
* if the condition evaluates to false.
*/
CondItem makeCondItem(int opcode, Chain trueJumps, Chain falseJumps) {
return new CondItem(opcode, trueJumps, falseJumps);
}
/** Make an item representing a conditional or unconditional jump.
* @param opcode The jump's opcode.
*/
CondItem makeCondItem(int opcode) {
return makeCondItem(opcode, null, null);
}
/** The base class of all items, which implements default behavior.
*/
abstract class Item {
/** The type code of values represented by this item.
*/
int typecode;
Item(int typecode) {
this.typecode = typecode;
}
/** Generate code to load this item onto stack.
*/
Item load() {
throw new AssertionError();
}
/** Generate code to store top of stack into this item.
*/
void store() {
throw new AssertionError("store unsupported: " + this);
}
/** Generate code to invoke method represented by this item.
*/
Item invoke() {
throw new AssertionError(this);
}
/** Generate code to use this item twice.
*/
void duplicate() {}
/** Generate code to avoid having to use this item.
*/
void drop() {}
/** Generate code to stash a copy of top of stack - of typecode toscode -
* under this item.
*/
void stash(int toscode) {
stackItem[toscode].duplicate();
}
/** Generate code to turn item into a testable condition.
*/
CondItem mkCond() {
load();
return makeCondItem(ifne);
}
/** Generate code to coerce item to given type code.
* @param targetcode The type code to coerce to.
*/
Item coerce(int targetcode) {
if (typecode == targetcode)
return this;
else {
load();
int typecode1 = Code.truncate(typecode);
int targetcode1 = Code.truncate(targetcode);
if (typecode1 != targetcode1) {
int offset = targetcode1 > typecode1 ? targetcode1 - 1
: targetcode1;
code.emitop0(i2l + typecode1 * 3 + offset);
}
if (targetcode != targetcode1) {
code.emitop0(int2byte + targetcode - BYTEcode);
}
return stackItem[targetcode];
}
}
/** Generate code to coerce item to given type.
* @param targettype The type to coerce to.
*/
Item coerce(Type targettype) {
return coerce(Code.typecode(targettype));
}
/** Return the width of this item on stack as a number of words.
*/
int width() {
return 0;
}
public abstract String toString();
}
/** An item representing a value on stack.
*/
class StackItem extends Item {
StackItem(int typecode) {
super(typecode);
}
Item load() {
return this;
}
void duplicate() {
code.emitop0(width() == 2 ? dup2 : dup);
}
void drop() {
code.emitop0(width() == 2 ? pop2 : pop);
}
void stash(int toscode) {
code.emitop0(
(width() == 2 ? dup_x2 : dup_x1) + 3 * (Code.width(toscode) - 1));
}
int width() {
return Code.width(typecode);
}
public String toString() {
return "stack(" + typecodeNames[typecode] + ")";
}
}
/** An item representing an indexed expression.
*/
class IndexedItem extends Item {
IndexedItem(Type type) {
super(Code.typecode(type));
}
Item load() {
code.emitop0(iaload + typecode);
return stackItem[typecode];
}
void store() {
code.emitop0(iastore + typecode);
}
void duplicate() {
code.emitop0(dup2);
}
void drop() {
code.emitop0(pop2);
}
void stash(int toscode) {
code.emitop0(dup_x2 + 3 * (Code.width(toscode) - 1));
}
int width() {
return 2;
}
public String toString() {
return "indexed(" + ByteCodes.typecodeNames[typecode] + ")";
}
}
/** An item representing `this' or `super'.
*/
class SelfItem extends Item {
/** Flag which determines whether this item represents `this' or `super'.
*/
boolean isSuper;
SelfItem(boolean isSuper) {
super(OBJECTcode);
this.isSuper = isSuper;
}
Item load() {
code.emitop0(aload_0);
return stackItem[typecode];
}
public String toString() {
return isSuper ? "super" : "this";
}
}
/** An item representing a local variable.
*/
class LocalItem extends Item {
/** The variable's register.
*/
int reg;
/** The variable's type.
*/
Type type;
LocalItem(Type type, int reg) {
super(Code.typecode(type));
Assert.check(reg >= 0);
this.type = type;
this.reg = reg;
}
Item load() {
if (reg <= 3)
code.emitop0(iload_0 + Code.truncate(typecode) * 4 + reg);
else
code.emitop1w(iload + Code.truncate(typecode), reg);
return stackItem[typecode];
}
void store() {
if (reg <= 3)
code.emitop0(istore_0 + Code.truncate(typecode) * 4 + reg);
else
code.emitop1w(istore + Code.truncate(typecode), reg);
code.setDefined(reg);
}
void incr(int x) {
if (typecode == INTcode && x >= -32768 && x <= 32767) {
code.emitop1w(iinc, reg, x);
} else {
load();
if (x >= 0) {
makeImmediateItem(syms.intType, x).load();
code.emitop0(iadd);
} else {
makeImmediateItem(syms.intType, -x).load();
code.emitop0(isub);
}
makeStackItem(syms.intType).coerce(typecode);
store();
}
}
public String toString() {
return "localItem(type=" + type + "; reg=" + reg + ")";
}
}
/** An item representing a static variable or method.
*/
class StaticItem extends Item {
/** The represented symbol.
*/
Symbol member;
StaticItem(Symbol member) {
super(Code.typecode(member.erasure(types)));
this.member = member;
}
Item load() {
code.emitop2(getstatic, pool.put(member));
return stackItem[typecode];
}
void store() {
code.emitop2(putstatic, pool.put(member));
}
Item invoke() {
MethodType mtype = (MethodType)member.erasure(types);
int rescode = Code.typecode(mtype.restype);
code.emitInvokestatic(pool.put(member), mtype);
return stackItem[rescode];
}
public String toString() {
return "static(" + member + ")";
}
}
/** An item representing a dynamic call site.
*/
class DynamicItem extends StaticItem {
DynamicItem(Symbol member) {
super(member);
}
Item load() {
assert false;
return null;
}
void store() {
assert false;
}
Item invoke() {
// assert target.hasNativeInvokeDynamic();
MethodType mtype = (MethodType)member.erasure(types);
int rescode = Code.typecode(mtype.restype);
code.emitInvokedynamic(pool.put(member), mtype);
return stackItem[rescode];
}
public String toString() {
return "dynamic(" + member + ")";
}
}
/** An item representing an instance variable or method.
*/
class MemberItem extends Item {
/** The represented symbol.
*/
Symbol member;
/** Flag that determines whether or not access is virtual.
*/
boolean nonvirtual;
MemberItem(Symbol member, boolean nonvirtual) {
super(Code.typecode(member.erasure(types)));
this.member = member;
this.nonvirtual = nonvirtual;
}
Item load() {
code.emitop2(getfield, pool.put(member));
return stackItem[typecode];
}
void store() {
code.emitop2(putfield, pool.put(member));
}
Item invoke() {
MethodType mtype = (MethodType)member.externalType(types);
int rescode = Code.typecode(mtype.restype);
if ((member.owner.flags() & Flags.INTERFACE) != 0 && !nonvirtual) {
code.emitInvokeinterface(pool.put(member), mtype);
} else if (nonvirtual) {
code.emitInvokespecial(pool.put(member), mtype);
} else {
code.emitInvokevirtual(pool.put(member), mtype);
}
return stackItem[rescode];
}
void duplicate() {
stackItem[OBJECTcode].duplicate();
}
void drop() {
stackItem[OBJECTcode].drop();
}
void stash(int toscode) {
stackItem[OBJECTcode].stash(toscode);
}
int width() {
return 1;
}
public String toString() {
return "member(" + member + (nonvirtual ? " nonvirtual)" : ")");
}
}
/** An item representing a literal.
*/
class ImmediateItem extends Item {
/** The literal's value.
*/
Object value;
ImmediateItem(Type type, Object value) {
super(Code.typecode(type));
this.value = value;
}
private void ldc() {
int idx = pool.put(value);
if (typecode == LONGcode || typecode == DOUBLEcode) {
code.emitop2(ldc2w, idx);
} else {
code.emitLdc(idx);
}
}
Item load() {
switch (typecode) {
case INTcode: case BYTEcode: case SHORTcode: case CHARcode:
int ival = ((Number)value).intValue();
if (-1 <= ival && ival <= 5)
code.emitop0(iconst_0 + ival);
else if (Byte.MIN_VALUE <= ival && ival <= Byte.MAX_VALUE)
code.emitop1(bipush, ival);
else if (Short.MIN_VALUE <= ival && ival <= Short.MAX_VALUE)
code.emitop2(sipush, ival);
else
ldc();
break;
case LONGcode:
long lval = ((Number)value).longValue();
if (lval == 0 || lval == 1)
code.emitop0(lconst_0 + (int)lval);
else
ldc();
break;
case FLOATcode:
float fval = ((Number)value).floatValue();
if (isPosZero(fval) || fval == 1.0 || fval == 2.0)
code.emitop0(fconst_0 + (int)fval);
else {
ldc();
}
break;
case DOUBLEcode:
double dval = ((Number)value).doubleValue();
if (isPosZero(dval) || dval == 1.0)
code.emitop0(dconst_0 + (int)dval);
else
ldc();
break;
case OBJECTcode:
ldc();
break;
default:
Assert.error();
}
return stackItem[typecode];
}
//where
/** Return true iff float number is positive 0.
*/
private boolean isPosZero(float x) {
return x == 0.0f && 1.0f / x > 0.0f;
}
/** Return true iff double number is positive 0.
*/
private boolean isPosZero(double x) {
return x == 0.0d && 1.0d / x > 0.0d;
}
CondItem mkCond() {
int ival = ((Number)value).intValue();
return makeCondItem(ival != 0 ? goto_ : dontgoto);
}
Item coerce(int targetcode) {
if (typecode == targetcode) {
return this;
} else {
switch (targetcode) {
case INTcode:
if (Code.truncate(typecode) == INTcode)
return this;
else
return new ImmediateItem(
syms.intType,
((Number)value).intValue());
case LONGcode:
return new ImmediateItem(
syms.longType,
((Number)value).longValue());
case FLOATcode:
return new ImmediateItem(
syms.floatType,
((Number)value).floatValue());
case DOUBLEcode:
return new ImmediateItem(
syms.doubleType,
((Number)value).doubleValue());
case BYTEcode:
return new ImmediateItem(
syms.byteType,
(int)(byte)((Number)value).intValue());
case CHARcode:
return new ImmediateItem(
syms.charType,
(int)(char)((Number)value).intValue());
case SHORTcode:
return new ImmediateItem(
syms.shortType,
(int)(short)((Number)value).intValue());
default:
return super.coerce(targetcode);
}
}
}
public String toString() {
return "immediate(" + value + ")";
}
}
/** An item representing an assignment expressions.
*/
class AssignItem extends Item {
/** The item representing the assignment's left hand side.
*/
Item lhs;
AssignItem(Item lhs) {
super(lhs.typecode);
this.lhs = lhs;
}
Item load() {
lhs.stash(typecode);
lhs.store();
return stackItem[typecode];
}
void duplicate() {
load().duplicate();
}
void drop() {
lhs.store();
}
void stash(int toscode) {
Assert.error();
}
int width() {
return lhs.width() + Code.width(typecode);
}
public String toString() {
return "assign(lhs = " + lhs + ")";
}
}
/** An item representing a conditional or unconditional jump.
*/
class CondItem extends Item {
/** A chain encomassing all jumps that can be taken
* if the condition evaluates to true.
*/
Chain trueJumps;
/** A chain encomassing all jumps that can be taken
* if the condition evaluates to false.
*/
Chain falseJumps;
/** The jump's opcode.
*/
int opcode;
/*
* An abstract syntax tree of this item. It is needed
* for branch entries in 'CharacterRangeTable' attribute.
*/
JCTree tree;
CondItem(int opcode, Chain truejumps, Chain falsejumps) {
super(BYTEcode);
this.opcode = opcode;
this.trueJumps = truejumps;
this.falseJumps = falsejumps;
}
Item load() {
Chain trueChain = null;
Chain falseChain = jumpFalse();
if (!isFalse()) {
code.resolve(trueJumps);
code.emitop0(iconst_1);
trueChain = code.branch(goto_);
}
if (falseChain != null) {
code.resolve(falseChain);
code.emitop0(iconst_0);
}
code.resolve(trueChain);
return stackItem[typecode];
}
void duplicate() {
load().duplicate();
}
void drop() {
load().drop();
}
void stash(int toscode) {
Assert.error();
}
CondItem mkCond() {
return this;
}
Chain jumpTrue() {
if (tree == null) return Code.mergeChains(trueJumps, code.branch(opcode));
// we should proceed further in -Xjcov mode only
int startpc = code.curCP();
Chain c = Code.mergeChains(trueJumps, code.branch(opcode));
code.crt.put(tree, CRTable.CRT_BRANCH_TRUE, startpc, code.curCP());
return c;
}
Chain jumpFalse() {
if (tree == null) return Code.mergeChains(falseJumps, code.branch(Code.negate(opcode)));
// we should proceed further in -Xjcov mode only
int startpc = code.curCP();
Chain c = Code.mergeChains(falseJumps, code.branch(Code.negate(opcode)));
code.crt.put(tree, CRTable.CRT_BRANCH_FALSE, startpc, code.curCP());
return c;
}
CondItem negate() {
CondItem c = new CondItem(Code.negate(opcode), falseJumps, trueJumps);
c.tree = tree;
return c;
}
int width() {
// a CondItem doesn't have a size on the stack per se.
throw new AssertionError();
}
boolean isTrue() {
return falseJumps == null && opcode == goto_;
}
boolean isFalse() {
return trueJumps == null && opcode == dontgoto;
}
public String toString() {
return "cond(" + Code.mnem(opcode) + ")";
}
}
}
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