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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
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* published by the Free Software Foundation.
*
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* 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.
*
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package org.graalvm.compiler.lir;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* A buffer to enqueue updates to a list. This avoids frequent re-sizing of the list and copying of
* list elements when insertions are done at multiple positions of the list. Additionally, it
* ensures that the list is not modified while it is, e.g., iterated, and instead only modified once
* after the iteration is done.
* <p>
* The buffer uses internal data structures to store the enqueued updates. To avoid allocations, a
* buffer can be re-used. Call the methods in the following order: {@link #init}, {@link #append},
* {@link #append}, ..., {@link #finish()}, {@link #init}, ...
* <p>
* Note: This class does not depend on LIRInstruction, so we could make it a generic utility class.
*/
public final class LIRInsertionBuffer {
/**
* The lir list where ops of this buffer should be inserted later (null when uninitialized).
*/
private List<LIRInstruction> lir;
/**
* List of insertion points. index and count are stored alternately: indexAndCount[i * 2]: the
* index into lir list where "count" ops should be inserted indexAndCount[i * 2 + 1]: the number
* of ops to be inserted at index
*/
private int[] indexAndCount;
private int indexAndCountSize;
/**
* The LIROps to be inserted.
*/
private final List<LIRInstruction> ops;
public LIRInsertionBuffer() {
indexAndCount = new int[8];
ops = new ArrayList<>(4);
}
/**
* Initialize this buffer. This method must be called before using {@link #append}.
*/
public void init(List<LIRInstruction> newLir) {
assert !initialized() : "already initialized";
assert indexAndCountSize == 0 && ops.size() == 0;
this.lir = newLir;
}
public boolean initialized() {
return lir != null;
}
public List<LIRInstruction> lirList() {
return lir;
}
/**
* Enqueue a new instruction that will be appended to the instruction list when
* {@link #finish()} is called. The new instruction is added <b>before</b> the existing
* instruction with the given index. This method can only be called with increasing values of
* index, e.g., once an instruction was appended with index 4, subsequent instructions can only
* be appended with index 4 or higher.
*/
public void append(int index, LIRInstruction op) {
int i = numberOfInsertionPoints() - 1;
if (i < 0 || indexAt(i) < index) {
appendNew(index, 1);
} else {
assert indexAt(i) == index : "can append LIROps in ascending order only";
assert countAt(i) > 0 : "check";
setCountAt(i, countAt(i) + 1);
}
ops.add(op);
assert verify();
}
/**
* Append all enqueued instructions to the instruction list. After that, {@link #init(List)} can
* be called again to re-use this buffer.
*/
public void finish() {
if (ops.size() > 0) {
int n = lir.size();
// increase size of instructions list
for (int i = 0; i < ops.size(); i++) {
lir.add(null);
}
// insert ops from buffer into instructions list
int opIndex = ops.size() - 1;
int ipIndex = numberOfInsertionPoints() - 1;
int fromIndex = n - 1;
int toIndex = lir.size() - 1;
while (ipIndex >= 0) {
int index = indexAt(ipIndex);
// make room after insertion point
while (fromIndex >= index) {
lir.set(toIndex--, lir.get(fromIndex--));
}
// insert ops from buffer
for (int i = countAt(ipIndex); i > 0; i--) {
lir.set(toIndex--, ops.get(opIndex--));
}
ipIndex--;
}
indexAndCountSize = 0;
ops.clear();
}
lir = null;
}
private void appendNew(int index, int count) {
int oldSize = indexAndCountSize;
int newSize = oldSize + 2;
if (newSize > this.indexAndCount.length) {
indexAndCount = Arrays.copyOf(indexAndCount, newSize * 2);
}
indexAndCount[oldSize] = index;
indexAndCount[oldSize + 1] = count;
this.indexAndCountSize = newSize;
}
private void setCountAt(int i, int value) {
indexAndCount[(i << 1) + 1] = value;
}
private int numberOfInsertionPoints() {
assert indexAndCount.length % 2 == 0 : "must have a count for each index";
return indexAndCountSize >> 1;
}
private int indexAt(int i) {
return indexAndCount[(i << 1)];
}
private int countAt(int i) {
return indexAndCount[(i << 1) + 1];
}
private boolean verify() {
int sum = 0;
int prevIdx = -1;
for (int i = 0; i < numberOfInsertionPoints(); i++) {
assert prevIdx < indexAt(i) : "index must be ordered ascending";
sum += countAt(i);
}
assert sum == ops.size() : "wrong total sum";
return true;
}
}