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/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. Alternatively, the contents of this file may be used under
* the terms of the GNU Lesser General Public License Version 2.1 or later,
* or the Apache License Version 2.0.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*/
package javassist.bytecode.stackmap;
import javassist.bytecode.*;
import java.util.HashMap;
import java.util.ArrayList;
/**
* A basic block is a sequence of bytecode that does not contain jump/branch
* instructions except at the last bytecode.
* Since Java7 or later does not allow JSR, this class throws an exception when
* it finds JSR.
*/
public class BasicBlock {
static class JsrBytecode extends BadBytecode {
JsrBytecode() { super("JSR"); }
}
protected int position, length;
protected int incoming; // the number of incoming branches.
protected BasicBlock[] exit; // null if the block is a leaf.
protected boolean stop; // true if the block ends with an unconditional jump.
protected Catch toCatch;
protected BasicBlock(int pos) {
position = pos;
length = 0;
incoming = 0;
}
public static BasicBlock find(BasicBlock[] blocks, int pos)
throws BadBytecode
{
for (int i = 0; i < blocks.length; i++) {
int iPos = blocks[i].position;
if (iPos <= pos && pos < iPos + blocks[i].length)
return blocks[i];
}
throw new BadBytecode("no basic block at " + pos);
}
public static class Catch {
public Catch next;
public BasicBlock body;
public int typeIndex;
Catch(BasicBlock b, int i, Catch c) {
body = b;
typeIndex = i;
next = c;
}
}
public String toString() {
StringBuffer sbuf = new StringBuffer();
String cname = this.getClass().getName();
int i = cname.lastIndexOf('.');
sbuf.append(i < 0 ? cname : cname.substring(i + 1));
sbuf.append("[");
toString2(sbuf);
sbuf.append("]");
return sbuf.toString();
}
protected void toString2(StringBuffer sbuf) {
sbuf.append("pos=").append(position).append(", len=")
.append(length).append(", in=").append(incoming)
.append(", exit{");
if (exit != null) {
for (int i = 0; i < exit.length; i++)
sbuf.append(exit[i].position).append(",");
}
sbuf.append("}, {");
Catch th = toCatch;
while (th != null) {
sbuf.append("(").append(th.body.position).append(", ")
.append(th.typeIndex).append("), ");
th = th.next;
}
sbuf.append("}");
}
/**
* A Mark indicates the position of a branch instruction
* or a branch target.
*/
static class Mark implements Comparable {
int position;
BasicBlock block;
BasicBlock[] jump;
boolean alwaysJmp; // true if an unconditional branch.
int size; // 0 unless the mark indicates RETURN etc.
Catch catcher;
Mark(int p) {
position = p;
block = null;
jump = null;
alwaysJmp = false;
size = 0;
catcher = null;
}
public int compareTo(Object obj) {
if (obj instanceof Mark) {
int pos = ((Mark)obj).position;
return position - pos;
}
return -1;
}
void setJump(BasicBlock[] bb, int s, boolean always) {
jump = bb;
size = s;
alwaysJmp = always;
}
}
public static class Maker {
/* Override these two methods if a subclass of BasicBlock must be
* instantiated.
*/
protected BasicBlock makeBlock(int pos) {
return new BasicBlock(pos);
}
protected BasicBlock[] makeArray(int size) {
return new BasicBlock[size];
}
private BasicBlock[] makeArray(BasicBlock b) {
BasicBlock[] array = makeArray(1);
array[0] = b;
return array;
}
private BasicBlock[] makeArray(BasicBlock b1, BasicBlock b2) {
BasicBlock[] array = makeArray(2);
array[0] = b1;
array[1] = b2;
return array;
}
public BasicBlock[] make(MethodInfo minfo) throws BadBytecode {
CodeAttribute ca = minfo.getCodeAttribute();
if (ca == null)
return null;
CodeIterator ci = ca.iterator();
return make(ci, 0, ci.getCodeLength(), ca.getExceptionTable());
}
public BasicBlock[] make(CodeIterator ci, int begin, int end,
ExceptionTable et)
throws BadBytecode
{
HashMap marks = makeMarks(ci, begin, end, et);
BasicBlock[] bb = makeBlocks(marks);
addCatchers(bb, et);
return bb;
}
/* Branch target
*/
private Mark makeMark(HashMap table, int pos) {
return makeMark0(table, pos, true, true);
}
/* Branch instruction.
* size > 0
*/
private Mark makeMark(HashMap table, int pos, BasicBlock[] jump,
int size, boolean always) {
Mark m = makeMark0(table, pos, false, false);
m.setJump(jump, size, always);
return m;
}
private Mark makeMark0(HashMap table, int pos,
boolean isBlockBegin, boolean isTarget) {
Integer p = new Integer(pos);
Mark m = (Mark)table.get(p);
if (m == null) {
m = new Mark(pos);
table.put(p, m);
}
if (isBlockBegin) {
if (m.block == null)
m.block = makeBlock(pos);
if (isTarget)
m.block.incoming++;
}
return m;
}
private HashMap makeMarks(CodeIterator ci, int begin, int end,
ExceptionTable et)
throws BadBytecode
{
ci.begin();
ci.move(begin);
HashMap marks = new HashMap();
while (ci.hasNext()) {
int index = ci.next();
if (index >= end)
break;
int op = ci.byteAt(index);
if ((Opcode.IFEQ <= op && op <= Opcode.IF_ACMPNE)
|| op == Opcode.IFNULL || op == Opcode.IFNONNULL) {
Mark to = makeMark(marks, index + ci.s16bitAt(index + 1));
Mark next = makeMark(marks, index + 3);
makeMark(marks, index, makeArray(to.block, next.block), 3, false);
}
else if (Opcode.GOTO <= op && op <= Opcode.LOOKUPSWITCH)
switch (op) {
case Opcode.GOTO :
makeGoto(marks, index, index + ci.s16bitAt(index + 1), 3);
break;
case Opcode.JSR :
makeJsr(marks, index, index + ci.s16bitAt(index + 1), 3);
break;
case Opcode.RET :
makeMark(marks, index, null, 2, true);
break;
case Opcode.TABLESWITCH : {
int pos = (index & ~3) + 4;
int low = ci.s32bitAt(pos + 4);
int high = ci.s32bitAt(pos + 8);
int ncases = high - low + 1;
BasicBlock[] to = makeArray(ncases + 1);
to[0] = makeMark(marks, index + ci.s32bitAt(pos)).block; // default branch target
int p = pos + 12;
int n = p + ncases * 4;
int k = 1;
while (p < n) {
to[k++] = makeMark(marks, index + ci.s32bitAt(p)).block;
p += 4;
}
makeMark(marks, index, to, n - index, true);
break; }
case Opcode.LOOKUPSWITCH : {
int pos = (index & ~3) + 4;
int ncases = ci.s32bitAt(pos + 4);
BasicBlock[] to = makeArray(ncases + 1);
to[0] = makeMark(marks, index + ci.s32bitAt(pos)).block; // default branch target
int p = pos + 8 + 4;
int n = p + ncases * 8 - 4;
int k = 1;
while (p < n) {
to[k++] = makeMark(marks, index + ci.s32bitAt(p)).block;
p += 8;
}
makeMark(marks, index, to, n - index, true);
break; }
}
else if ((Opcode.IRETURN <= op && op <= Opcode.RETURN) || op == Opcode.ATHROW)
makeMark(marks, index, null, 1, true);
else if (op == Opcode.GOTO_W)
makeGoto(marks, index, index + ci.s32bitAt(index + 1), 5);
else if (op == Opcode.JSR_W)
makeJsr(marks, index, index + ci.s32bitAt(index + 1), 5);
else if (op == Opcode.WIDE && ci.byteAt(index + 1) == Opcode.RET)
makeMark(marks, index, null, 4, true);
}
if (et != null) {
int i = et.size();
while (--i >= 0) {
makeMark0(marks, et.startPc(i), true, false);
makeMark(marks, et.handlerPc(i));
}
}
return marks;
}
private void makeGoto(HashMap marks, int pos, int target, int size) {
Mark to = makeMark(marks, target);
BasicBlock[] jumps = makeArray(to.block);
makeMark(marks, pos, jumps, size, true);
}
/*
* We could ignore JSR since Java 7 or later does not allow it.
* See The JVM Spec. Sec. 4.10.2.5.
*/
protected void makeJsr(HashMap marks, int pos, int target, int size) throws BadBytecode {
/*
Mark to = makeMark(marks, target);
Mark next = makeMark(marks, pos + size);
BasicBlock[] jumps = makeArray(to.block, next.block);
makeMark(marks, pos, jumps, size, false);
*/
throw new JsrBytecode();
}
private BasicBlock[] makeBlocks(HashMap markTable) {
Mark[] marks = (Mark[])markTable.values()
.toArray(new Mark[markTable.size()]);
java.util.Arrays.sort(marks);
ArrayList blocks = new ArrayList();
int i = 0;
BasicBlock prev;
if (marks.length > 0 && marks[0].position == 0 && marks[0].block != null)
prev = getBBlock(marks[i++]);
else
prev = makeBlock(0);
blocks.add(prev);
while (i < marks.length) {
Mark m = marks[i++];
BasicBlock bb = getBBlock(m);
if (bb == null) {
// the mark indicates a branch instruction
if (prev.length > 0) {
// the previous mark already has exits.
prev = makeBlock(prev.position + prev.length);
blocks.add(prev);
}
prev.length = m.position + m.size - prev.position;
prev.exit = m.jump;
prev.stop = m.alwaysJmp;
}
else {
// the mark indicates a branch target
if (prev.length == 0) {
prev.length = m.position - prev.position;
bb.incoming++;
prev.exit = makeArray(bb);
}
else {
// the previous mark already has exits.
if (prev.position + prev.length < m.position) {
// dead code is found.
prev = makeBlock(prev.position + prev.length);
blocks.add(prev);
prev.length = m.position - prev.position;
// the incoming flow from dead code is not counted
// bb.incoming++;
prev.stop = true; // because the incoming flow is not counted.
prev.exit = makeArray(bb);
}
}
blocks.add(bb);
prev = bb;
}
}
return (BasicBlock[])blocks.toArray(makeArray(blocks.size()));
}
private static BasicBlock getBBlock(Mark m) {
BasicBlock b = m.block;
if (b != null && m.size > 0) {
b.exit = m.jump;
b.length = m.size;
b.stop = m.alwaysJmp;
}
return b;
}
private void addCatchers(BasicBlock[] blocks, ExceptionTable et)
throws BadBytecode
{
if (et == null)
return;
int i = et.size();
while (--i >= 0) {
BasicBlock handler = find(blocks, et.handlerPc(i));
int start = et.startPc(i);
int end = et.endPc(i);
int type = et.catchType(i);
handler.incoming--;
for (int k = 0; k < blocks.length; k++) {
BasicBlock bb = blocks[k];
int iPos = bb.position;
if (start <= iPos && iPos < end) {
bb.toCatch = new Catch(handler, type, bb.toCatch);
handler.incoming++;
}
}
}
}
}
}
