org.mozilla.classfile.SuperBlock Maven / Gradle / Ivy
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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.classfile;
/**
* A super block is defined as a contiguous chunk of code with a single entry point and multiple
* exit points (therefore ending in an unconditional jump or the end of the method). This is used to
* emulate OpenJDK's compiler, which outputs stack map frames at the start of every super block
* except the method start.
*/
final class SuperBlock {
SuperBlock(int index, int start, int end, int[] initialLocals) {
this.index = index;
this.start = start;
this.end = end;
locals = new int[initialLocals.length];
System.arraycopy(initialLocals, 0, locals, 0, initialLocals.length);
stack = new int[0];
isInitialized = false;
isInQueue = false;
}
int getIndex() {
return index;
}
int[] getLocals() {
int[] copy = new int[locals.length];
System.arraycopy(locals, 0, copy, 0, locals.length);
return copy;
}
/**
* Get a copy of the super block's locals without any trailing TOP types.
*
* This is useful for actual writing stack maps; during the computation of stack map types,
* all local arrays have the same size; the max locals for the method. In addition, DOUBLE and
* LONG types have trailing TOP types because they occupy two words. For writing purposes, these
* are not useful.
*/
int[] getTrimmedLocals() {
int last = locals.length - 1;
// Exclude all of the trailing TOPs not bound to a DOUBLE/LONG
while (last >= 0
&& locals[last] == TypeInfo.TOP
&& !TypeInfo.isTwoWords(locals[last - 1])) {
last--;
}
last++;
// Exclude trailing TOPs following a DOUBLE/LONG
int size = last;
for (int i = 0; i < last; i++) {
if (TypeInfo.isTwoWords(locals[i])) {
size--;
}
}
int[] copy = new int[size];
for (int i = 0, j = 0; i < size; i++, j++) {
copy[i] = locals[j];
if (TypeInfo.isTwoWords(locals[j])) {
j++;
}
}
return copy;
}
int[] getStack() {
int[] copy = new int[stack.length];
System.arraycopy(stack, 0, copy, 0, stack.length);
return copy;
}
boolean merge(int[] locals, int localsTop, int[] stack, int stackTop, ConstantPool pool) {
if (!isInitialized) {
System.arraycopy(locals, 0, this.locals, 0, localsTop);
this.stack = new int[stackTop];
System.arraycopy(stack, 0, this.stack, 0, stackTop);
isInitialized = true;
return true;
} else if (this.locals.length == localsTop && this.stack.length == stackTop) {
boolean localsChanged = mergeState(this.locals, locals, localsTop, pool);
boolean stackChanged = mergeState(this.stack, stack, stackTop, pool);
return localsChanged || stackChanged;
} else {
if (ClassFileWriter.StackMapTable.DEBUGSTACKMAP) {
System.out.println("bad merge");
System.out.println("current type state:");
TypeInfo.print(this.locals, this.stack, pool);
System.out.println("incoming type state:");
TypeInfo.print(locals, localsTop, stack, stackTop, pool);
}
throw new IllegalArgumentException("bad merge attempt");
}
}
/**
* Merge an operand stack or local variable array with incoming state.
*
*
They are treated the same way; by this point, it should already be ensured that the array
* sizes are the same, which is the only additional constraint that is imposed on merging
* operand stacks (the local variable array is always the same size).
*/
private static boolean mergeState(int[] current, int[] incoming, int size, ConstantPool pool) {
boolean changed = false;
for (int i = 0; i < size; i++) {
int currentType = current[i];
current[i] = TypeInfo.merge(current[i], incoming[i], pool);
if (currentType != current[i]) {
changed = true;
}
}
return changed;
}
int getStart() {
return start;
}
int getEnd() {
return end;
}
@Override
public String toString() {
return "sb " + index;
}
boolean isInitialized() {
return isInitialized;
}
void setInitialized(boolean b) {
isInitialized = b;
}
boolean isInQueue() {
return isInQueue;
}
void setInQueue(boolean b) {
isInQueue = b;
}
private int index;
private int start;
private int end;
private int[] locals;
private int[] stack;
private boolean isInitialized;
private boolean isInQueue;
}