/**
* Copy numbytes from src to dst. Assumption either the ranges are non overlapping, or src >= dst
* + 4. Also, src and dst are 4 byte aligned and numBytes is a multiple of 4.
*
* @param dst the destination addr
* @param src the source addr
* @param numBytes the number of bytes top copy
*/
@Inline
public static void aligned32Copy(Address dst, Address src, Offset numBytes) {
if (USE_NATIVE && numBytes.sGT(Offset.fromIntSignExtend(NATIVE_THRESHOLD))) {
memcopy(dst, src, numBytes.toWord().toExtent());
} else {
if (VM.BuildFor64Addr) {
Word wordMask = Word.one().lsh(LOG_BYTES_IN_ADDRESS).minus(Word.one());
Word srcAlignment = src.toWord().and(wordMask);
if (srcAlignment.EQ(dst.toWord().and(wordMask))) {
Offset i = Offset.zero();
if (srcAlignment.EQ(Word.fromIntZeroExtend(BYTES_IN_INT))) {
dst.store(src.loadInt(i), i);
i = i.plus(BYTES_IN_INT);
}
Word endAlignment =
srcAlignment.plus(numBytes).and(Word.fromIntSignExtend(BYTES_IN_ADDRESS - 1));
numBytes = numBytes.minus(endAlignment.toOffset());
for (; i.sLT(numBytes); i = i.plus(BYTES_IN_ADDRESS)) {
dst.store(src.loadWord(i), i);
}
if (!endAlignment.isZero()) {
dst.store(src.loadInt(i), i);
}
return;
}
}
// normal case: 32 bit or (64 bit not aligned)
for (Offset i = Offset.zero(); i.sLT(numBytes); i = i.plus(BYTES_IN_INT)) {
dst.store(src.loadInt(i), i);
}
}
}
@NoInline
@Unpreemptible
public static boolean casFromBiased(
Object o, Offset lockOffset, Word oldLockWord, Word changed, int cnt) {
RVMThread me = RVMThread.getCurrentThread();
Word id = oldLockWord.and(TL_THREAD_ID_MASK);
if (id.isZero()) {
if (false) VM.sysWriteln("id is zero - easy case.");
return Synchronization.tryCompareAndSwap(o, lockOffset, oldLockWord, changed);
} else {
if (false) VM.sysWriteln("id = ", id);
int slot = id.toInt() >> TL_THREAD_ID_SHIFT;
if (false) VM.sysWriteln("slot = ", slot);
RVMThread owner = RVMThread.threadBySlot[slot];
if (owner == me /* I own it, so I can unbias it trivially. This occurs
when we are inflating due to, for example, wait() */
|| owner == null /* the thread that owned it is dead, so it's safe to
unbias. */) {
// note that we use a CAS here, but it's only needed in the case
// that owner==null, since in that case some other thread may also
// be unbiasing.
return Synchronization.tryCompareAndSwap(o, lockOffset, oldLockWord, changed);
} else {
boolean result = false;
// NB. this may stop a thread other than the one that had the bias,
// if that thread died and some other thread took its slot. that's
// why we do a CAS below. it's only needed if some other thread
// had seen the owner be null (which may happen if we came here after
// a new thread took the slot while someone else came here when the
// slot was still null). if it was the case that everyone else had
// seen a non-null owner, then the pair handshake would serve as
// sufficient synchronization (the id would identify the set of threads
// that shared that id's communicationLock). oddly, that means that
// this whole thing could be "simplified" to acquire the
// communicationLock even if the owner was null. but that would be
// goofy.
if (false) VM.sysWriteln("entering pair handshake");
owner.beginPairHandshake();
if (false) VM.sysWriteln("done with that");
Word newLockWord = Magic.getWordAtOffset(o, lockOffset);
result = Synchronization.tryCompareAndSwap(o, lockOffset, oldLockWord, changed);
owner.endPairHandshake();
if (false) VM.sysWriteln("that worked.");
return result;
}
}
}
/**
* Copy copyBytes from src to dst. Assumption: either the ranges are non overlapping, or {@code
* src >= dst + 4}. Also, src and dst are 4 byte aligned and numBytes is a multiple of 4.
*
* @param dst the destination addr
* @param src the source addr
* @param copyBytes the number of bytes top copy
*/
public static void aligned32Copy(Address dst, Address src, int copyBytes) {
if (VM.VerifyAssertions) {
VM._assert(copyBytes >= 0);
VM._assert((copyBytes & (BYTES_IN_INT - 1)) == 0);
VM._assert(src.toWord().and(Word.fromIntZeroExtend(BYTES_IN_INT - 1)).isZero());
VM._assert(dst.toWord().and(Word.fromIntZeroExtend(BYTES_IN_INT - 1)).isZero());
VM._assert(src.plus(copyBytes).LE(dst) || src.GE(dst.plus(BYTES_IN_INT)));
}
if (USE_NATIVE && copyBytes > NATIVE_THRESHOLD) {
memcopy(dst, src, copyBytes);
} else {
Offset numBytes = Offset.fromIntSignExtend(copyBytes);
if (BYTES_IN_COPY == 8 && copyBytes != 0) {
Word wordMask = Word.fromIntZeroExtend(BYTES_IN_COPY - 1);
Word srcAlignment = src.toWord().and(wordMask);
if (srcAlignment.EQ(dst.toWord().and(wordMask))) {
Offset i = Offset.zero();
if (srcAlignment.EQ(Word.fromIntZeroExtend(BYTES_IN_INT))) {
copy4Bytes(dst.plus(i), src.plus(i));
i = i.plus(BYTES_IN_INT);
}
Word endAlignment = srcAlignment.plus(numBytes).and(wordMask);
numBytes = numBytes.minus(endAlignment.toOffset());
for (; i.sLT(numBytes); i = i.plus(BYTES_IN_COPY)) {
copy8Bytes(dst.plus(i), src.plus(i));
}
if (!endAlignment.isZero()) {
copy4Bytes(dst.plus(i), src.plus(i));
}
return;
}
}
// normal case: 32 bit or (64 bit not aligned)
for (Offset i = Offset.zero(); i.sLT(numBytes); i = i.plus(BYTES_IN_INT)) {
copy4Bytes(dst.plus(i), src.plus(i));
}
}
}
@NoInline
@NoNullCheck
@Unpreemptible
public static void lock(Object o, Offset lockOffset) {
if (STATS) fastLocks++;
Word threadId = Word.fromIntZeroExtend(RVMThread.getCurrentThread().getLockingId());
for (int cnt = 0; ; cnt++) {
Word old = Magic.getWordAtOffset(o, lockOffset);
Word stat = old.and(TL_STAT_MASK);
boolean tryToInflate = false;
if (stat.EQ(TL_STAT_BIASABLE)) {
Word id = old.and(TL_THREAD_ID_MASK);
if (id.isZero()) {
if (ENABLE_BIASED_LOCKING) {
// lock is unbiased, bias it in our favor and grab it
if (Synchronization.tryCompareAndSwap(
o, lockOffset, old, old.or(threadId).plus(TL_LOCK_COUNT_UNIT))) {
Magic.isync();
return;
}
} else {
// lock is unbiased but biasing is NOT allowed, so turn it into
// a thin lock
if (Synchronization.tryCompareAndSwap(
o, lockOffset, old, old.or(threadId).or(TL_STAT_THIN))) {
Magic.isync();
return;
}
}
} else if (id.EQ(threadId)) {
// lock is biased in our favor
Word changed = old.plus(TL_LOCK_COUNT_UNIT);
if (!changed.and(TL_LOCK_COUNT_MASK).isZero()) {
setDedicatedU16(o, lockOffset, changed);
return;
} else {
tryToInflate = true;
}
} else {
if (casFromBiased(o, lockOffset, old, biasBitsToThinBits(old), cnt)) {
continue; // don't spin, since it's thin now
}
}
} else if (stat.EQ(TL_STAT_THIN)) {
Word id = old.and(TL_THREAD_ID_MASK);
if (id.isZero()) {
if (Synchronization.tryCompareAndSwap(o, lockOffset, old, old.or(threadId))) {
Magic.isync();
return;
}
} else if (id.EQ(threadId)) {
Word changed = old.plus(TL_LOCK_COUNT_UNIT);
if (changed.and(TL_LOCK_COUNT_MASK).isZero()) {
tryToInflate = true;
} else if (Synchronization.tryCompareAndSwap(o, lockOffset, old, changed)) {
Magic.isync();
return;
}
} else if (cnt > retryLimit) {
tryToInflate = true;
}
} else {
if (VM.VerifyAssertions) VM._assert(stat.EQ(TL_STAT_FAT));
// lock is fat. contend on it.
if (Lock.getLock(getLockIndex(old)).lockHeavy(o)) {
return;
}
}
if (tryToInflate) {
if (STATS) slowLocks++;
// the lock is not fat, is owned by someone else, or else the count wrapped.
// attempt to inflate it (this may fail, in which case we'll just harmlessly
// loop around) and lock it (may also fail, if we get the wrong lock). if it
// succeeds, we're done.
// NB: this calls into our attemptToMarkInflated() method, which will do the
// Right Thing if the lock is biased to someone else.
if (inflateAndLock(o, lockOffset)) {
return;
}
} else {
RVMThread.yield();
}
}
}