org.objectweb.asm.commons.JSRInlinerAdapter Maven / Gradle / Ivy
// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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package org.objectweb.asm.commons;
import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.LabelNode;
import org.objectweb.asm.tree.LocalVariableNode;
import org.objectweb.asm.tree.LookupSwitchInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TableSwitchInsnNode;
import org.objectweb.asm.tree.TryCatchBlockNode;
/**
* A {@link org.objectweb.asm.MethodVisitor} that removes JSR instructions and inlines the
* referenced subroutines.
*
* Explanation of how it works TODO
*
* @author Niko Matsakis
*/
public class JSRInlinerAdapter extends MethodNode implements Opcodes {
private static final boolean LOGGING = false;
/** For each label that is jumped to by a JSR, we create a BitSet instance. */
private final Map subroutineHeads = new HashMap();
/**
* This subroutine instance denotes the line of execution that is not contained within any
* subroutine; i.e., the "subroutine" that is executing when a method first begins.
*/
private final BitSet mainSubroutine = new BitSet();
/**
* This BitSet contains the index of every instruction that belongs to more than one subroutine.
* This should not happen often.
*/
final BitSet dualCitizens = new BitSet();
/**
* Constructs a new JSRInliner. Subclasses must not use this constructor. Instead, they must
* use the {@link #JSRInlinerAdapter(int, MethodVisitor, int, String, String, String, String[])}
* version.
*
* @param mv the MethodVisitor to send the resulting inlined method code to (use
* null for none).
* @param access the method's access flags (see {@link Opcodes}). This parameter also indicates if
* the method is synthetic and/or deprecated.
* @param name the method's name.
* @param desc the method's descriptor (see {@link Type}).
* @param signature the method's signature. May be null.
* @param exceptions the internal names of the method's exception classes (see {@link
* Type#getInternalName() getInternalName}). May be null.
* @throws IllegalStateException If a subclass calls this constructor.
*/
public JSRInlinerAdapter(
final MethodVisitor mv,
final int access,
final String name,
final String desc,
final String signature,
final String[] exceptions) {
this(Opcodes.ASM6, mv, access, name, desc, signature, exceptions);
if (getClass() != JSRInlinerAdapter.class) {
throw new IllegalStateException();
}
}
/**
* Constructs a new JSRInliner.
*
* @param api the ASM API version implemented by this visitor. Must be one of {@link
* Opcodes#ASM4}, {@link Opcodes#ASM5} or {@link Opcodes#ASM6}.
* @param mv the MethodVisitor to send the resulting inlined method code to (use
* null for none).
* @param access the method's access flags (see {@link Opcodes}). This parameter also indicates if
* the method is synthetic and/or deprecated.
* @param name the method's name.
* @param desc the method's descriptor (see {@link Type}).
* @param signature the method's signature. May be null.
* @param exceptions the internal names of the method's exception classes (see {@link
* Type#getInternalName() getInternalName}). May be null.
*/
protected JSRInlinerAdapter(
final int api,
final MethodVisitor mv,
final int access,
final String name,
final String desc,
final String signature,
final String[] exceptions) {
super(api, access, name, desc, signature, exceptions);
this.mv = mv;
}
/** Detects a JSR instruction and sets a flag to indicate we will need to do inlining. */
@Override
public void visitJumpInsn(final int opcode, final Label lbl) {
super.visitJumpInsn(opcode, lbl);
LabelNode ln = ((JumpInsnNode) instructions.getLast()).label;
if (opcode == JSR && !subroutineHeads.containsKey(ln)) {
subroutineHeads.put(ln, new BitSet());
}
}
/**
* If any JSRs were seen, triggers the inlining process. Otherwise, forwards the byte codes
* untouched.
*/
@Override
public void visitEnd() {
if (!subroutineHeads.isEmpty()) {
markSubroutines();
if (LOGGING) {
log(mainSubroutine.toString());
Iterator it = subroutineHeads.values().iterator();
while (it.hasNext()) {
BitSet sub = it.next();
log(sub.toString());
}
}
emitCode();
}
// Forward the translate opcodes on if appropriate:
if (mv != null) {
accept(mv);
}
}
/**
* Walks the method and determines which internal subroutine(s), if any, each instruction is a
* method of.
*/
private void markSubroutines() {
BitSet anyvisited = new BitSet();
// First walk the main subroutine and find all those instructions which
// can be reached without invoking any JSR at all
markSubroutineWalk(mainSubroutine, 0, anyvisited);
// Go through the head of each subroutine and find any nodes reachable
// to that subroutine without following any JSR links.
for (Iterator> it = subroutineHeads.entrySet().iterator();
it.hasNext();
) {
Map.Entry entry = it.next();
LabelNode lab = entry.getKey();
BitSet sub = entry.getValue();
int index = instructions.indexOf(lab);
markSubroutineWalk(sub, index, anyvisited);
}
}
/**
* Performs a depth first search walking the normal byte code path starting at index,
* and adding each instruction encountered into the subroutine sub. After this walk
* is complete, iterates over the exception handlers to ensure that we also include those byte
* codes which are reachable through an exception that may be thrown during the execution of the
* subroutine. Invoked from markSubroutines().
*
* @param sub the subroutine whose instructions must be computed.
* @param index an instruction of this subroutine.
* @param anyvisited indexes of the already visited instructions, i.e. marked as part of this
* subroutine or any previously computed subroutine.
*/
private void markSubroutineWalk(final BitSet sub, final int index, final BitSet anyvisited) {
if (LOGGING) {
log("markSubroutineWalk: sub=" + sub + " index=" + index);
}
// First find those instructions reachable via normal execution
markSubroutineWalkDFS(sub, index, anyvisited);
// Now, make sure we also include any applicable exception handlers
boolean loop = true;
while (loop) {
loop = false;
for (Iterator it = tryCatchBlocks.iterator(); it.hasNext(); ) {
TryCatchBlockNode trycatch = it.next();
if (LOGGING) {
// TODO use of default toString().
log("Scanning try/catch " + trycatch);
}
// If the handler has already been processed, skip it.
int handlerindex = instructions.indexOf(trycatch.handler);
if (sub.get(handlerindex)) {
continue;
}
int startindex = instructions.indexOf(trycatch.start);
int endindex = instructions.indexOf(trycatch.end);
int nextbit = sub.nextSetBit(startindex);
if (nextbit != -1 && nextbit < endindex) {
if (LOGGING) {
log(
"Adding exception handler: "
+ startindex
+ '-'
+ endindex
+ " due to "
+ nextbit
+ " handler "
+ handlerindex);
}
markSubroutineWalkDFS(sub, handlerindex, anyvisited);
loop = true;
}
}
}
}
/**
* Performs a simple DFS of the instructions, assigning each to the subroutine sub.
* Starts from index. Invoked only by markSubroutineWalk().
*
* @param sub the subroutine whose instructions must be computed.
* @param index an instruction of this subroutine.
* @param anyvisited indexes of the already visited instructions, i.e. marked as part of this
* subroutine or any previously computed subroutine.
*/
private void markSubroutineWalkDFS(final BitSet sub, int index, final BitSet anyvisited) {
while (true) {
AbstractInsnNode node = instructions.get(index);
// don't visit a node twice
if (sub.get(index)) {
return;
}
sub.set(index);
// check for those nodes already visited by another subroutine
if (anyvisited.get(index)) {
dualCitizens.set(index);
if (LOGGING) {
log("Instruction #" + index + " is dual citizen.");
}
}
anyvisited.set(index);
if (node.getType() == AbstractInsnNode.JUMP_INSN && node.getOpcode() != JSR) {
// we do not follow recursively called subroutines here; but any
// other sort of branch we do follow
JumpInsnNode jnode = (JumpInsnNode) node;
int destidx = instructions.indexOf(jnode.label);
markSubroutineWalkDFS(sub, destidx, anyvisited);
}
if (node.getType() == AbstractInsnNode.TABLESWITCH_INSN) {
TableSwitchInsnNode tsnode = (TableSwitchInsnNode) node;
int destidx = instructions.indexOf(tsnode.dflt);
markSubroutineWalkDFS(sub, destidx, anyvisited);
for (int i = tsnode.labels.size() - 1; i >= 0; --i) {
LabelNode l = tsnode.labels.get(i);
destidx = instructions.indexOf(l);
markSubroutineWalkDFS(sub, destidx, anyvisited);
}
}
if (node.getType() == AbstractInsnNode.LOOKUPSWITCH_INSN) {
LookupSwitchInsnNode lsnode = (LookupSwitchInsnNode) node;
int destidx = instructions.indexOf(lsnode.dflt);
markSubroutineWalkDFS(sub, destidx, anyvisited);
for (int i = lsnode.labels.size() - 1; i >= 0; --i) {
LabelNode l = lsnode.labels.get(i);
destidx = instructions.indexOf(l);
markSubroutineWalkDFS(sub, destidx, anyvisited);
}
}
// check to see if this opcode falls through to the next instruction
// or not; if not, return.
switch (instructions.get(index).getOpcode()) {
case GOTO:
case RET:
case TABLESWITCH:
case LOOKUPSWITCH:
case IRETURN:
case LRETURN:
case FRETURN:
case DRETURN:
case ARETURN:
case RETURN:
case ATHROW:
/*
* note: this either returns from this subroutine, or a parent
* subroutine which invoked it
*/
return;
}
// Use tail recursion here in the form of an outer while loop to
// avoid our stack growing needlessly:
index++;
// We implicitly assumed above that execution can always fall
// through to the next instruction after a JSR. But a subroutine may
// never return, in which case the code after the JSR is unreachable
// and can be anything. In particular, it can seem to fall off the
// end of the method, so we must handle this case here (we could
// instead detect whether execution can return or not from a JSR,
// but this is more complicated).
if (index >= instructions.size()) {
return;
}
}
}
/**
* Creates the new instructions, inlining each instantiation of each subroutine until the code is
* fully elaborated.
*/
private void emitCode() {
LinkedList worklist = new LinkedList();
// Create an instantiation of the "root" subroutine, which is just the
// main routine
worklist.add(new Instantiation(null, mainSubroutine));
// Emit instantiations of each subroutine we encounter, including the
// main subroutine
InsnList newInstructions = new InsnList();
List newTryCatchBlocks = new ArrayList();
List newLocalVariables = new ArrayList();
while (!worklist.isEmpty()) {
Instantiation inst = worklist.removeFirst();
emitSubroutine(inst, worklist, newInstructions, newTryCatchBlocks, newLocalVariables);
}
instructions = newInstructions;
tryCatchBlocks = newTryCatchBlocks;
localVariables = newLocalVariables;
}
/**
* Emits one instantiation of one subroutine, specified by instant. May add new
* instantiations that are invoked by this one to the worklist parameter, and new
* try/catch blocks to newTryCatchBlocks.
*
* @param instant the instantiation that must be performed.
* @param worklist list of the instantiations that remain to be done.
* @param newInstructions the instruction list to which the instantiated code must be appended.
* @param newTryCatchBlocks the exception handler list to which the instantiated handlers must be
* appended.
* @param newLocalVariables the local variables list to which the instantiated local variables
* must be appended.
*/
private void emitSubroutine(
final Instantiation instant,
final List worklist,
final InsnList newInstructions,
final List newTryCatchBlocks,
final List newLocalVariables) {
LabelNode duplbl = null;
if (LOGGING) {
log("--------------------------------------------------------");
log("Emitting instantiation of subroutine " + instant.subroutine);
}
// Emit the relevant instructions for this instantiation, translating
// labels and jump targets as we go:
for (int i = 0, c = instructions.size(); i < c; i++) {
AbstractInsnNode insn = instructions.get(i);
Instantiation owner = instant.findOwner(i);
// Always remap labels:
if (insn.getType() == AbstractInsnNode.LABEL) {
// Translate labels into their renamed equivalents.
// Avoid adding the same label more than once. Note
// that because we own this instruction the gotoTable
// and the rangeTable will always agree.
LabelNode ilbl = (LabelNode) insn;
LabelNode remap = instant.rangeLabel(ilbl);
if (LOGGING) {
// TODO use of default toString().
log("Translating lbl #" + i + ':' + ilbl + " to " + remap);
}
if (remap != duplbl) {
newInstructions.add(remap);
duplbl = remap;
}
continue;
}
// We don't want to emit instructions that were already
// emitted by a subroutine higher on the stack. Note that
// it is still possible for a given instruction to be
// emitted twice because it may belong to two subroutines
// that do not invoke each other.
if (owner != instant) {
continue;
}
if (LOGGING) {
log("Emitting inst #" + i);
}
if (insn.getOpcode() == RET) {
// Translate RET instruction(s) to a jump to the return label
// for the appropriate instantiation. The problem is that the
// subroutine may "fall through" to the ret of a parent
// subroutine; therefore, to find the appropriate ret label we
// find the lowest subroutine on the stack that claims to own
// this instruction. See the class javadoc comment for an
// explanation on why this technique is safe (note: it is only
// safe if the input is verifiable).
LabelNode retlabel = null;
for (Instantiation p = instant; p != null; p = p.previous) {
if (p.subroutine.get(i)) {
retlabel = p.returnLabel;
}
}
if (retlabel == null) {
// This is only possible if the mainSubroutine owns a RET
// instruction, which should never happen for verifiable
// code.
throw new RuntimeException("Instruction #" + i + " is a RET not owned by any subroutine");
}
newInstructions.add(new JumpInsnNode(GOTO, retlabel));
} else if (insn.getOpcode() == JSR) {
LabelNode lbl = ((JumpInsnNode) insn).label;
BitSet sub = subroutineHeads.get(lbl);
Instantiation newinst = new Instantiation(instant, sub);
LabelNode startlbl = newinst.gotoLabel(lbl);
if (LOGGING) {
log(" Creating instantiation of subr " + sub);
}
// Rather than JSRing, we will jump to the inline version and
// push NULL for what was once the return value. This hack
// allows us to avoid doing any sort of data flow analysis to
// figure out which instructions manipulate the old return value
// pointer which is now known to be unneeded.
newInstructions.add(new InsnNode(ACONST_NULL));
newInstructions.add(new JumpInsnNode(GOTO, startlbl));
newInstructions.add(newinst.returnLabel);
// Insert this new instantiation into the queue to be emitted
// later.
worklist.add(newinst);
} else {
newInstructions.add(insn.clone(instant));
}
}
// Emit try/catch blocks that are relevant to this method.
for (Iterator it = tryCatchBlocks.iterator(); it.hasNext(); ) {
TryCatchBlockNode trycatch = it.next();
if (LOGGING) {
// TODO use of default toString().
log(
"try catch block original labels="
+ trycatch.start
+ '-'
+ trycatch.end
+ "->"
+ trycatch.handler);
}
final LabelNode start = instant.rangeLabel(trycatch.start);
final LabelNode end = instant.rangeLabel(trycatch.end);
// Ignore empty try/catch regions
if (start == end) {
if (LOGGING) {
log(" try catch block empty in this subroutine");
}
continue;
}
final LabelNode handler = instant.gotoLabel(trycatch.handler);
if (LOGGING) {
// TODO use of default toString().
log(" try catch block new labels=" + start + '-' + end + "->" + handler);
}
if (start == null || end == null || handler == null) {
throw new RuntimeException("Internal error!");
}
newTryCatchBlocks.add(new TryCatchBlockNode(start, end, handler, trycatch.type));
}
for (Iterator it = localVariables.iterator(); it.hasNext(); ) {
LocalVariableNode lvnode = it.next();
if (LOGGING) {
log("local var " + lvnode.name);
}
final LabelNode start = instant.rangeLabel(lvnode.start);
final LabelNode end = instant.rangeLabel(lvnode.end);
if (start == end) {
if (LOGGING) {
log(" local variable empty in this sub");
}
continue;
}
newLocalVariables.add(
new LocalVariableNode(
lvnode.name, lvnode.desc, lvnode.signature, start, end, lvnode.index));
}
}
private static void log(final String str) {
System.err.println(str);
}
/**
* A class that represents an instantiation of a subroutine. Each instantiation has an associate
* "stack" --- which is a listing of those instantiations that were active when this particular
* instance of this subroutine was invoked. Each instantiation also has a map from the original
* labels of the program to the labels appropriate for this instantiation, and finally a label to
* return to.
*/
private class Instantiation extends AbstractMap {
/** Previous instantiations; the stack must be statically predictable to be inlinable. */
final Instantiation previous;
/** The subroutine this is an instantiation of. */
public final BitSet subroutine;
/**
* This table maps Labels from the original source to Labels pointing at code specific to this
* instantiation, for use in remapping try/catch blocks,as well as gotos.
*
* Note that in the presence of dual citizens instructions, that is, instructions which
* belong to more than one subroutine due to the merging of control flow without a RET
* instruction, we will map the target label of a GOTO to the label used by the instantiation
* lowest on the stack. This avoids code duplication during inlining in most cases.
*
* @see #findOwner(int)
*/
public final Map rangeTable = new HashMap();
/** All returns for this instantiation will be mapped to this label */
public final LabelNode returnLabel;
Instantiation(final Instantiation prev, final BitSet sub) {
previous = prev;
subroutine = sub;
for (Instantiation p = prev; p != null; p = p.previous) {
if (p.subroutine == sub) {
throw new RuntimeException("Recursive invocation of " + sub);
}
}
// Determine the label to return to when this subroutine terminates
// via RET: note that the main subroutine never terminates via RET.
if (prev != null) {
returnLabel = new LabelNode();
} else {
returnLabel = null;
}
// Each instantiation will remap the labels from the code above to
// refer to its particular copy of its own instructions. Note that
// we collapse labels which point at the same instruction into one:
// this is fairly common as we are often ignoring large chunks of
// instructions, so what were previously distinct labels become
// duplicates.
LabelNode duplbl = null;
for (int i = 0, c = instructions.size(); i < c; i++) {
AbstractInsnNode insn = instructions.get(i);
if (insn.getType() == AbstractInsnNode.LABEL) {
LabelNode ilbl = (LabelNode) insn;
if (duplbl == null) {
// if we already have a label pointing at this spot,
// don't recreate it.
duplbl = new LabelNode();
}
// Add an entry in the rangeTable for every label
// in the original code which points at the next
// instruction of our own to be emitted.
rangeTable.put(ilbl, duplbl);
} else if (findOwner(i) == this) {
// We will emit this instruction, so clear the 'duplbl' flag
// since the next Label will refer to a distinct
// instruction.
duplbl = null;
}
}
}
/**
* Returns the "owner" of a particular instruction relative to this instantiation: the owner
* referes to the Instantiation which will emit the version of this instruction that we will
* execute.
*
* Typically, the return value is either this or null. this
* indicates that this instantiation will generate the version of this instruction that
* we will execute, and null indicates that this instantiation never executes the
* given instruction.
*
*
Sometimes, however, an instruction can belong to multiple subroutines; this is called a
* "dual citizen" instruction (though it may belong to more than 2 subroutines), and occurs when
* multiple subroutines branch to common points of control. In this case, the owner is the
* subroutine that appears lowest on the stack, and which also owns the instruction in question.
*
* @param i the index of the instruction in the original code
* @return the "owner" of a particular instruction relative to this instantiation.
*/
public Instantiation findOwner(final int i) {
if (!subroutine.get(i)) {
return null;
}
if (!dualCitizens.get(i)) {
return this;
}
Instantiation own = this;
for (Instantiation p = previous; p != null; p = p.previous) {
if (p.subroutine.get(i)) {
own = p;
}
}
return own;
}
/**
* Looks up the label l in the gotoTable, thus translating it from a
* Label in the original code, to a Label in the inlined code that is appropriate for use by an
* instruction that branched to the original label.
*
* @param l The label we will be translating
* @return a label for use by a branch instruction in the inlined code
* @see #rangeLabel
*/
public LabelNode gotoLabel(final LabelNode l) {
// owner should never be null, because owner is only null
// if an instruction cannot be reached from this subroutine
Instantiation owner = findOwner(instructions.indexOf(l));
return owner.rangeTable.get(l);
}
/**
* Looks up the label l in the rangeTable, thus translating it from a
* Label in the original code, to a Label in the inlined code that is appropriate for use by an
* try/catch or variable use annotation.
*
* @param l The label we will be translating
* @return a label for use by a try/catch or variable annotation in the original code
* @see #rangeTable
*/
public LabelNode rangeLabel(final LabelNode l) {
return rangeTable.get(l);
}
// AbstractMap implementation
@Override
public Set> entrySet() {
return null;
}
@Override
public LabelNode get(final Object o) {
return gotoLabel((LabelNode) o);
}
}
}