void
MBasicBlock::inheritPhis(MBasicBlock *header)
{
MResumePoint *headerRp = header->entryResumePoint();
size_t stackDepth = headerRp->numOperands();
for (size_t slot = 0; slot < stackDepth; slot++) {
MDefinition *exitDef = getSlot(slot);
MDefinition *loopDef = headerRp->getOperand(slot);
if (!loopDef->isPhi()) {
MOZ_ASSERT(loopDef->block()->id() < header->id());
MOZ_ASSERT(loopDef == exitDef);
continue;
}
// Phis are allocated by NewPendingLoopHeader.
MPhi *phi = loopDef->toPhi();
MOZ_ASSERT(phi->numOperands() == 2);
// The entry definition is always the leftmost input to the phi.
MDefinition *entryDef = phi->getOperand(0);
if (entryDef != exitDef)
continue;
// If the entryDef is the same as exitDef, then we must propagate the
// phi down to this successor. This chance was missed as part of
// setBackedge() because exits are not captured in resume points.
setSlot(slot, phi);
}
}
MBasicBlock *
MBasicBlock::NewAsmJS(MIRGraph &graph, CompileInfo &info, MBasicBlock *pred, Kind kind)
{
MBasicBlock *block = new MBasicBlock(graph, info, /* entryPC = */ NULL, kind);
if (!block->init())
return NULL;
if (pred) {
block->stackPosition_ = pred->stackPosition_;
if (block->kind_ == PENDING_LOOP_HEADER) {
for (size_t i = 0; i < block->stackPosition_; i++) {
MDefinition *predSlot = pred->getSlot(i);
JS_ASSERT(predSlot->type() != MIRType_Value);
MPhi *phi = MPhi::New(i, predSlot->type());
JS_ALWAYS_TRUE(phi->reserveLength(2));
phi->addInput(predSlot);
block->addPhi(phi);
block->setSlot(i, phi);
}
} else {
block->copySlots(pred);
}
if (!block->predecessors_.append(pred))
return NULL;
}
return block;
}
// Remove the CFG edge between |pred| and |block|, after releasing the phi
// operands on that edge and discarding any definitions consequently made dead.
bool
ValueNumberer::removePredecessorAndDoDCE(MBasicBlock *block, MBasicBlock *pred)
{
MOZ_ASSERT(!block->isMarked(),
"Block marked unreachable should have predecessors removed already");
// Before removing the predecessor edge, scan the phi operands for that edge
// for dead code before they get removed.
if (!block->phisEmpty()) {
uint32_t index = pred->positionInPhiSuccessor();
for (MPhiIterator iter(block->phisBegin()), end(block->phisEnd()); iter != end; ++iter) {
MPhi *phi = *iter;
MOZ_ASSERT(!values_.has(phi), "Visited phi in block having predecessor removed");
MDefinition *op = phi->getOperand(index);
if (op == phi)
continue;
// Set the operand to the phi itself rather than just releasing it
// because removePredecessor expects to have something to release.
phi->replaceOperand(index, phi);
if (!handleUseReleased(op, DontSetUseRemoved) || !processDeadDefs())
return false;
}
}
block->removePredecessor(pred);
return true;
}
bool
MBasicBlock::inherit(MBasicBlock *pred, uint32_t popped)
{
if (pred) {
stackPosition_ = pred->stackPosition_;
JS_ASSERT(stackPosition_ >= popped);
stackPosition_ -= popped;
if (kind_ != PENDING_LOOP_HEADER)
copySlots(pred);
} else if (pc()) {
uint32_t stackDepth = info().script()->analysis()->getCode(pc()).stackDepth;
stackPosition_ = info().firstStackSlot() + stackDepth;
JS_ASSERT(stackPosition_ >= popped);
stackPosition_ -= popped;
} else {
stackPosition_ = info().firstStackSlot();
}
JS_ASSERT(info_.nslots() >= stackPosition_);
JS_ASSERT(!entryResumePoint_);
if (pc()) {
// Propagate the caller resume point from the inherited block.
MResumePoint *callerResumePoint = pred ? pred->callerResumePoint() : NULL;
// Create a resume point using our initial stack state.
entryResumePoint_ = new MResumePoint(this, pc(), callerResumePoint, MResumePoint::ResumeAt);
if (!entryResumePoint_->init())
return false;
}
if (pred) {
if (!predecessors_.append(pred))
return false;
if (kind_ == PENDING_LOOP_HEADER) {
for (size_t i = 0; i < stackDepth(); i++) {
MPhi *phi = MPhi::New(i);
if (!phi->addInputSlow(pred->getSlot(i)))
return false;
addPhi(phi);
setSlot(i, phi);
if (entryResumePoint())
entryResumePoint()->setOperand(i, phi);
}
} else if (entryResumePoint()) {
for (size_t i = 0; i < stackDepth(); i++)
entryResumePoint()->setOperand(i, getSlot(i));
}
} else if (entryResumePoint()) {
/*
* Don't leave the operands uninitialized for the caller, as it may not
* initialize them later on.
*/
for (size_t i = 0; i < stackDepth(); i++)
entryResumePoint()->clearOperand(i);
}
return true;
}
// Remove the CFG edge between |pred| and |block|, after releasing the phi
// operands on that edge and discarding any definitions consequently made dead.
bool
ValueNumberer::removePredecessorAndDoDCE(MBasicBlock* block, MBasicBlock* pred, size_t predIndex)
{
MOZ_ASSERT(!block->isMarked(),
"Block marked unreachable should have predecessors removed already");
// Before removing the predecessor edge, scan the phi operands for that edge
// for dead code before they get removed.
MOZ_ASSERT(nextDef_ == nullptr);
for (MPhiIterator iter(block->phisBegin()), end(block->phisEnd()); iter != end; ) {
MPhi* phi = *iter++;
MOZ_ASSERT(!values_.has(phi), "Visited phi in block having predecessor removed");
MDefinition* op = phi->getOperand(predIndex);
phi->removeOperand(predIndex);
nextDef_ = iter != end ? *iter : nullptr;
if (!handleUseReleased(op, DontSetUseRemoved) || !processDeadDefs())
return false;
// If |nextDef_| became dead while we had it pinned, advance the iterator
// and discard it now.
while (nextDef_ && !nextDef_->hasUses()) {
phi = nextDef_->toPhi();
iter++;
nextDef_ = iter != end ? *iter : nullptr;
discardDefsRecursively(phi);
}
}
nextDef_ = nullptr;
block->removePredecessorWithoutPhiOperands(pred, predIndex);
return true;
}
// Remove the CFG edge between |pred| and |block|, after releasing the phi
// operands on that edge and discarding any definitions consequently made dead.
bool
ValueNumberer::removePredecessorAndDoDCE(MBasicBlock *block, MBasicBlock *pred, size_t predIndex)
{
MOZ_ASSERT(!block->isMarked(),
"Block marked unreachable should have predecessors removed already");
// Before removing the predecessor edge, scan the phi operands for that edge
// for dead code before they get removed.
MOZ_ASSERT(nextDef_ == nullptr);
for (MPhiIterator iter(block->phisBegin()), end(block->phisEnd()); iter != end; ) {
MPhi *phi = *iter++;
MOZ_ASSERT(!values_.has(phi), "Visited phi in block having predecessor removed");
MDefinition *op = phi->getOperand(predIndex);
phi->removeOperand(predIndex);
nextDef_ = *iter;
if (!handleUseReleased(op, DontSetUseRemoved) || !processDeadDefs())
return false;
}
nextDef_ = nullptr;
block->removePredecessorWithoutPhiOperands(pred, predIndex);
return true;
}
// Determine whether the possible value of start (a phi node within the loop)
// can become smaller than an initial value at loop entry.
bool
Loop::nonDecreasing(MDefinition *initial, MDefinition *start)
{
MDefinitionVector worklist;
MDefinitionVector seen;
if (!worklist.append(start))
return false;
while (!worklist.empty()) {
MDefinition *def = worklist.popCopy();
bool duplicate = false;
for (size_t i = 0; i < seen.length() && !duplicate; i++) {
if (seen[i] == def)
duplicate = true;
}
if (duplicate)
continue;
if (!seen.append(def))
return false;
if (def->type() != MIRType_Int32)
return false;
if (!isInLoop(def)) {
if (def != initial)
return false;
continue;
}
if (def->isPhi()) {
MPhi *phi = def->toPhi();
for (size_t i = 0; i < phi->numOperands(); i++) {
if (!worklist.append(phi->getOperand(i)))
return false;
}
continue;
}
if (def->isAdd()) {
if (def->toAdd()->specialization() != MIRType_Int32)
return false;
MDefinition *lhs = def->toAdd()->getOperand(0);
MDefinition *rhs = def->toAdd()->getOperand(1);
if (!rhs->isConstant())
return false;
Value v = rhs->toConstant()->value();
if (!v.isInt32() || v.toInt32() < 0)
return false;
if (!worklist.append(lhs))
return false;
continue;
}
return false;
}
return true;
}
void
MBasicBlock::specializePhis()
{
for (MPhiIterator iter = phisBegin(); iter != phisEnd(); iter++) {
MPhi *phi = *iter;
phi->specializeType();
}
}
bool
MBasicBlock::specializePhis()
{
for (MPhiIterator iter = phisBegin(); iter != phisEnd(); iter++) {
MPhi *phi = *iter;
if (!phi->specializeType())
return false;
}
return true;
}
MBasicBlock*
MBasicBlock::New(MIRGraph& graph, const CompileInfo& info, MBasicBlock* pred, Kind kind)
{
BytecodeSite* site = new(graph.alloc()) BytecodeSite();
MBasicBlock* block = new(graph.alloc()) MBasicBlock(graph, info, site, kind);
if (!block->init())
return nullptr;
if (pred) {
block->stackPosition_ = pred->stackPosition_;
if (block->kind_ == PENDING_LOOP_HEADER) {
size_t nphis = block->stackPosition_;
size_t nfree = graph.phiFreeListLength();
TempAllocator& alloc = graph.alloc();
MPhi* phis = nullptr;
if (nphis > nfree) {
phis = alloc.allocateArray<MPhi>(nphis - nfree);
if (!phis)
return nullptr;
}
// Note: Phis are inserted in the same order as the slots.
for (size_t i = 0; i < nphis; i++) {
MDefinition* predSlot = pred->getSlot(i);
MOZ_ASSERT(predSlot->type() != MIRType::Value);
MPhi* phi;
if (i < nfree)
phi = graph.takePhiFromFreeList();
else
phi = phis + (i - nfree);
new(phi) MPhi(alloc, predSlot->type());
phi->addInlineInput(predSlot);
// Add append Phis in the block.
block->addPhi(phi);
block->setSlot(i, phi);
}
} else {
block->copySlots(pred);
}
if (!block->predecessors_.append(pred))
return nullptr;
}
return block;
}
bool
MBasicBlock::addPredecessorPopN(TempAllocator& alloc, MBasicBlock* pred, uint32_t popped)
{
MOZ_ASSERT(pred);
MOZ_ASSERT(predecessors_.length() > 0);
// Predecessors must be finished, and at the correct stack depth.
MOZ_ASSERT(pred->hasLastIns());
MOZ_ASSERT(pred->stackPosition_ == stackPosition_ + popped);
for (uint32_t i = 0, e = stackPosition_; i < e; ++i) {
MDefinition* mine = getSlot(i);
MDefinition* other = pred->getSlot(i);
if (mine != other) {
// If the current instruction is a phi, and it was created in this
// basic block, then we have already placed this phi and should
// instead append to its operands.
if (mine->isPhi() && mine->block() == this) {
MOZ_ASSERT(predecessors_.length());
if (!mine->toPhi()->addInputSlow(other))
return false;
} else {
// Otherwise, create a new phi node.
MPhi* phi;
if (mine->type() == other->type())
phi = MPhi::New(alloc.fallible(), mine->type());
else
phi = MPhi::New(alloc.fallible());
if (!phi)
return false;
addPhi(phi);
// Prime the phi for each predecessor, so input(x) comes from
// predecessor(x).
if (!phi->reserveLength(predecessors_.length() + 1))
return false;
for (size_t j = 0, numPreds = predecessors_.length(); j < numPreds; ++j) {
MOZ_ASSERT(predecessors_[j]->getSlot(i) == mine);
phi->addInput(mine);
}
phi->addInput(other);
setSlot(i, phi);
if (entryResumePoint())
entryResumePoint()->replaceOperand(i, phi);
}
}
}
return predecessors_.append(pred);
}
void
MBasicBlock::discardAllPhiOperands()
{
for (MPhiIterator iter = phisBegin(); iter != phisEnd(); iter++) {
MPhi *phi = *iter;
for (size_t i = 0, e = phi->numOperands(); i < e; i++)
phi->discardOperand(i);
}
for (MBasicBlock **pred = predecessors_.begin(); pred != predecessors_.end(); pred++)
(*pred)->setSuccessorWithPhis(NULL, 0);
}
bool
MBasicBlock::inheritPhisFromBackedge(MBasicBlock* backedge, bool* hadTypeChange)
{
// We must be a pending loop header
MOZ_ASSERT(kind_ == PENDING_LOOP_HEADER);
size_t stackDepth = entryResumePoint()->stackDepth();
for (size_t slot = 0; slot < stackDepth; slot++) {
// Get the value stack-slot of the back edge.
MDefinition* exitDef = backedge->getSlot(slot);
// Get the value of the loop header.
MDefinition* loopDef = entryResumePoint()->getOperand(slot);
if (loopDef->block() != this) {
// If we are finishing a pending loop header, then we need to ensure
// that all operands are phis. This is usualy the case, except for
// object/arrays build with generators, in which case we share the
// same allocations across all blocks.
MOZ_ASSERT(loopDef->block()->id() < id());
MOZ_ASSERT(loopDef == exitDef);
continue;
}
// Phis are allocated by NewPendingLoopHeader.
MPhi* entryDef = loopDef->toPhi();
MOZ_ASSERT(entryDef->block() == this);
if (entryDef == exitDef) {
// If the exit def is the same as the entry def, make a redundant
// phi. Since loop headers have exactly two incoming edges, we
// know that that's just the first input.
//
// Note that we eliminate later rather than now, to avoid any
// weirdness around pending continue edges which might still hold
// onto phis.
exitDef = entryDef->getOperand(0);
}
bool typeChange = false;
if (!entryDef->addInputSlow(exitDef))
return false;
if (!entryDef->checkForTypeChange(exitDef, &typeChange))
return false;
*hadTypeChange |= typeChange;
setSlot(slot, entryDef);
}
return true;
}
bool
MBasicBlock::specializePhis(TempAllocator& alloc)
{
if (specialized_)
return true;
specialized_ = true;
for (MPhiIterator iter = phisBegin(); iter != phisEnd(); iter++) {
MPhi* phi = *iter;
if (!phi->specializeType(alloc))
return false;
}
return true;
}
bool
MBasicBlock::setBackedgeWasm(MBasicBlock* pred)
{
// Predecessors must be finished, and at the correct stack depth.
MOZ_ASSERT(hasLastIns());
MOZ_ASSERT(pred->hasLastIns());
MOZ_ASSERT(stackDepth() == pred->stackDepth());
// We must be a pending loop header
MOZ_ASSERT(kind_ == PENDING_LOOP_HEADER);
// Add exit definitions to each corresponding phi at the entry.
// Note: Phis are inserted in the same order as the slots. (see
// MBasicBlock::New)
size_t slot = 0;
for (MPhiIterator phi = phisBegin(); phi != phisEnd(); phi++, slot++) {
MPhi* entryDef = *phi;
MDefinition* exitDef = pred->getSlot(slot);
// Assert that we already placed phis for each slot.
MOZ_ASSERT(entryDef->block() == this);
// Assert that the phi already has the correct type.
MOZ_ASSERT(entryDef->type() == exitDef->type());
MOZ_ASSERT(entryDef->type() != MIRType::Value);
if (entryDef == exitDef) {
// If the exit def is the same as the entry def, make a redundant
// phi. Since loop headers have exactly two incoming edges, we
// know that that's just the first input.
//
// Note that we eliminate later rather than now, to avoid any
// weirdness around pending continue edges which might still hold
// onto phis.
exitDef = entryDef->getOperand(0);
}
// Phis always have room for 2 operands, so this can't fail.
MOZ_ASSERT(phi->numOperands() == 1);
entryDef->addInlineInput(exitDef);
MOZ_ASSERT(slot < pred->stackDepth());
setSlot(slot, entryDef);
}
// We are now a loop header proper
kind_ = LOOP_HEADER;
return predecessors_.append(pred);
}
bool
MBasicBlock::addPredecessorPopN(MBasicBlock *pred, uint32_t popped)
{
JS_ASSERT(pred);
JS_ASSERT(predecessors_.length() > 0);
// Predecessors must be finished, and at the correct stack depth.
JS_ASSERT(pred->lastIns_);
JS_ASSERT(pred->stackPosition_ == stackPosition_ + popped);
for (uint32_t i = 0; i < stackPosition_; i++) {
MDefinition *mine = getSlot(i);
MDefinition *other = pred->getSlot(i);
if (mine != other) {
// If the current instruction is a phi, and it was created in this
// basic block, then we have already placed this phi and should
// instead append to its operands.
if (mine->isPhi() && mine->block() == this) {
JS_ASSERT(predecessors_.length());
if (!mine->toPhi()->addInputSlow(other))
return false;
} else {
// Otherwise, create a new phi node.
MPhi *phi = MPhi::New(i);
addPhi(phi);
// Prime the phi for each predecessor, so input(x) comes from
// predecessor(x).
if (!phi->initLength(predecessors_.length() + 1))
return false;
for (size_t j = 0; j < predecessors_.length(); j++) {
JS_ASSERT(predecessors_[j]->getSlot(i) == mine);
phi->setOperand(j, mine);
}
phi->setOperand(predecessors_.length(), other);
setSlot(i, phi);
if (entryResumePoint())
entryResumePoint()->replaceOperand(i, phi);
}
}
}
return predecessors_.append(pred);
}
bool
LBlock::init(TempAllocator& alloc)
{
// Count the number of LPhis we'll need.
size_t numLPhis = 0;
for (MPhiIterator i(block_->phisBegin()), e(block_->phisEnd()); i != e; ++i) {
MPhi* phi = *i;
switch (phi->type()) {
case MIRType::Value: numLPhis += BOX_PIECES; break;
case MIRType::Int64: numLPhis += INT64_PIECES; break;
default: numLPhis += 1; break;
}
}
// Allocate space for the LPhis.
if (!phis_.init(alloc, numLPhis))
return false;
// For each MIR phi, set up LIR phis as appropriate. We'll fill in their
// operands on each incoming edge, and set their definitions at the start of
// their defining block.
size_t phiIndex = 0;
size_t numPreds = block_->numPredecessors();
for (MPhiIterator i(block_->phisBegin()), e(block_->phisEnd()); i != e; ++i) {
MPhi* phi = *i;
MOZ_ASSERT(phi->numOperands() == numPreds);
int numPhis;
switch (phi->type()) {
case MIRType::Value: numPhis = BOX_PIECES; break;
case MIRType::Int64: numPhis = INT64_PIECES; break;
default: numPhis = 1; break;
}
for (int i = 0; i < numPhis; i++) {
LAllocation* inputs = alloc.allocateArray<LAllocation>(numPreds);
if (!inputs)
return false;
void* addr = &phis_[phiIndex++];
LPhi* lphi = new (addr) LPhi(phi, inputs);
lphi->setBlock(this);
}
}
return true;
}
// Test whether there are any phis in |header| which are newly optimizable, as a
// result of optimizations done inside the loop. This is not a sparse approach,
// but restarting is rare enough in practice. Termination is ensured by
// discarding the phi triggering the iteration.
bool
ValueNumberer::loopHasOptimizablePhi(MBasicBlock* header) const
{
// If the header is unreachable, don't bother re-optimizing it.
if (header->isMarked())
return false;
// Rescan the phis for any that can be simplified, since they may be reading
// values from backedges.
for (MPhiIterator iter(header->phisBegin()), end(header->phisEnd()); iter != end; ++iter) {
MPhi* phi = *iter;
MOZ_ASSERT(phi->hasUses(), "Missed an unused phi");
if (phi->operandIfRedundant() || hasLeader(phi, header))
return true; // Phi can be simplified.
}
return false;
}
// A loop is about to be made reachable only through an OSR entry into one of
// its nested loops. Fix everything up.
bool
ValueNumberer::fixupOSROnlyLoop(MBasicBlock* block, MBasicBlock* backedge)
{
// Create an empty and unreachable(!) block which jumps to |block|. This
// allows |block| to remain marked as a loop header, so we don't have to
// worry about moving a different block into place as the new loop header,
// which is hard, especially if the OSR is into a nested loop. Doing all
// that would produce slightly more optimal code, but this is so
// extraordinarily rare that it isn't worth the complexity.
MBasicBlock* fake = MBasicBlock::New(graph_, block->info(), nullptr, MBasicBlock::NORMAL);
if (fake == nullptr)
return false;
graph_.insertBlockBefore(block, fake);
fake->setImmediateDominator(fake);
fake->addNumDominated(1);
fake->setDomIndex(fake->id());
fake->setUnreachable();
// Create zero-input phis to use as inputs for any phis in |block|.
// Again, this is a little odd, but it's the least-odd thing we can do
// without significant complexity.
for (MPhiIterator iter(block->phisBegin()), end(block->phisEnd()); iter != end; ++iter) {
MPhi* phi = *iter;
MPhi* fakePhi = MPhi::New(graph_.alloc(), phi->type());
fake->addPhi(fakePhi);
if (!phi->addInputSlow(fakePhi))
return false;
}
fake->end(MGoto::New(graph_.alloc(), block));
if (!block->addPredecessorWithoutPhis(fake))
return false;
// Restore |backedge| as |block|'s loop backedge.
block->clearLoopHeader();
block->setLoopHeader(backedge);
JitSpew(JitSpew_GVN, " Created fake block%u", fake->id());
hasOSRFixups_ = true;
return true;
}
MBasicBlock *
MBasicBlock::NewAsmJS(MIRGraph &graph, CompileInfo &info, MBasicBlock *pred, Kind kind)
{
MBasicBlock *block = new(graph.alloc()) MBasicBlock(graph, info, BytecodeSite(), kind);
if (!block->init())
return nullptr;
if (pred) {
block->stackPosition_ = pred->stackPosition_;
if (block->kind_ == PENDING_LOOP_HEADER) {
size_t nphis = block->stackPosition_;
TempAllocator &alloc = graph.alloc();
MPhi *phis = (MPhi*)alloc.allocateArray<sizeof(MPhi)>(nphis);
if (!phis)
return nullptr;
// Note: Phis are inserted in the same order as the slots.
for (size_t i = 0; i < nphis; i++) {
MDefinition *predSlot = pred->getSlot(i);
JS_ASSERT(predSlot->type() != MIRType_Value);
MPhi *phi = new(phis + i) MPhi(alloc, predSlot->type());
JS_ALWAYS_TRUE(phi->reserveLength(2));
phi->addInput(predSlot);
// Add append Phis in the block.
block->addPhi(phi);
block->setSlot(i, phi);
}
} else {
block->copySlots(pred);
}
if (!block->predecessors_.append(pred))
return nullptr;
}
return block;
}
AbortReason
MBasicBlock::setBackedge(MBasicBlock *pred)
{
// Predecessors must be finished, and at the correct stack depth.
JS_ASSERT(lastIns_);
JS_ASSERT(pred->lastIns_);
JS_ASSERT(pred->stackDepth() == entryResumePoint()->stackDepth());
// We must be a pending loop header
JS_ASSERT(kind_ == PENDING_LOOP_HEADER);
bool hadTypeChange = false;
// Add exit definitions to each corresponding phi at the entry.
for (MPhiIterator phi = phisBegin(); phi != phisEnd(); phi++) {
MPhi *entryDef = *phi;
MDefinition *exitDef = pred->slots_[entryDef->slot()];
// Assert that we already placed phis for each slot.
JS_ASSERT(entryDef->block() == this);
if (entryDef == exitDef) {
// If the exit def is the same as the entry def, make a redundant
// phi. Since loop headers have exactly two incoming edges, we
// know that that's just the first input.
//
// Note that we eliminate later rather than now, to avoid any
// weirdness around pending continue edges which might still hold
// onto phis.
exitDef = entryDef->getOperand(0);
}
bool typeChange = false;
if (!entryDef->addInputSlow(exitDef, &typeChange))
return AbortReason_Alloc;
hadTypeChange |= typeChange;
JS_ASSERT(entryDef->slot() < pred->stackDepth());
setSlot(entryDef->slot(), entryDef);
}
if (hadTypeChange) {
for (MPhiIterator phi = phisBegin(); phi != phisEnd(); phi++)
phi->removeOperand(phi->numOperands() - 1);
return AbortReason_Disable;
}
// We are now a loop header proper
kind_ = LOOP_HEADER;
if (!predecessors_.append(pred))
return AbortReason_Alloc;
return AbortReason_NoAbort;
}
void
MBasicBlock::inheritPhis(MBasicBlock *header)
{
for (MPhiIterator iter = header->phisBegin(); iter != header->phisEnd(); iter++) {
MPhi *phi = *iter;
JS_ASSERT(phi->numOperands() == 2);
// The entry definition is always the leftmost input to the phi.
MDefinition *entryDef = phi->getOperand(0);
MDefinition *exitDef = getSlot(phi->slot());
if (entryDef != exitDef)
continue;
// If the entryDef is the same as exitDef, then we must propagate the
// phi down to this successor. This chance was missed as part of
// setBackedge() because exits are not captured in resume points.
setSlot(phi->slot(), phi);
}
}
bool
MBasicBlock::setBackedge(MBasicBlock *pred)
{
// Predecessors must be finished, and at the correct stack depth.
JS_ASSERT(lastIns_);
JS_ASSERT(pred->lastIns_);
JS_ASSERT(pred->stackDepth() == entryResumePoint()->stackDepth());
// We must be a pending loop header
JS_ASSERT(kind_ == PENDING_LOOP_HEADER);
// Add exit definitions to each corresponding phi at the entry.
for (uint32_t i = 0; i < pred->stackDepth(); i++) {
MPhi *entryDef = entryResumePoint()->getOperand(i)->toPhi();
MDefinition *exitDef = pred->slots_[i];
// Assert that we already placed phis for each slot.
JS_ASSERT(entryDef->block() == this);
if (entryDef == exitDef) {
// If the exit def is the same as the entry def, make a redundant
// phi. Since loop headers have exactly two incoming edges, we
// know that that's just the first input.
//
// Note that we eliminate later rather than now, to avoid any
// weirdness around pending continue edges which might still hold
// onto phis.
exitDef = entryDef->getOperand(0);
}
if (!entryDef->addInput(exitDef))
return false;
setSlot(i, entryDef);
}
// We are now a loop header proper
kind_ = LOOP_HEADER;
return predecessors_.append(pred);
}
bool
LBlock::init(TempAllocator& alloc)
{
// Count the number of LPhis we'll need.
size_t numLPhis = 0;
for (MPhiIterator i(block_->phisBegin()), e(block_->phisEnd()); i != e; ++i) {
MPhi* phi = *i;
numLPhis += (phi->type() == MIRType_Value) ? BOX_PIECES : 1;
}
// Allocate space for the LPhis.
if (!phis_.init(alloc, numLPhis))
return false;
// For each MIR phi, set up LIR phis as appropriate. We'll fill in their
// operands on each incoming edge, and set their definitions at the start of
// their defining block.
size_t phiIndex = 0;
size_t numPreds = block_->numPredecessors();
for (MPhiIterator i(block_->phisBegin()), e(block_->phisEnd()); i != e; ++i) {
MPhi* phi = *i;
MOZ_ASSERT(phi->numOperands() == numPreds);
int numPhis = (phi->type() == MIRType_Value) ? BOX_PIECES : 1;
for (int i = 0; i < numPhis; i++) {
void* array = alloc.allocateArray<sizeof(LAllocation)>(numPreds);
LAllocation* inputs = static_cast<LAllocation*>(array);
if (!inputs)
return false;
// MSVC 2015 cannot handle "new (&phis_[phiIndex++])"
void* addr = &phis_[phiIndex++];
LPhi* lphi = new (addr) LPhi(phi, inputs);
lphi->setBlock(this);
}
}
return true;
}
void
MBasicBlock::setLoopHeader(MBasicBlock* newBackedge)
{
MOZ_ASSERT(!isLoopHeader());
kind_ = LOOP_HEADER;
size_t numPreds = numPredecessors();
MOZ_ASSERT(numPreds != 0);
size_t lastIndex = numPreds - 1;
size_t oldIndex = 0;
for (; ; ++oldIndex) {
MOZ_ASSERT(oldIndex < numPreds);
MBasicBlock* pred = getPredecessor(oldIndex);
if (pred == newBackedge)
break;
}
// Set the loop backedge to be the last element in predecessors_.
Swap(predecessors_[oldIndex], predecessors_[lastIndex]);
// If we have phis, reorder their operands accordingly.
if (!phisEmpty()) {
getPredecessor(oldIndex)->setSuccessorWithPhis(this, oldIndex);
getPredecessor(lastIndex)->setSuccessorWithPhis(this, lastIndex);
for (MPhiIterator iter(phisBegin()), end(phisEnd()); iter != end; ++iter) {
MPhi* phi = *iter;
MDefinition* last = phi->getOperand(oldIndex);
MDefinition* old = phi->getOperand(lastIndex);
phi->replaceOperand(oldIndex, old);
phi->replaceOperand(lastIndex, last);
}
}
MOZ_ASSERT(newBackedge->loopHeaderOfBackedge() == this);
MOZ_ASSERT(backedge() == newBackedge);
}
bool
MBasicBlock::setBackedgeAsmJS(MBasicBlock *pred)
{
// Predecessors must be finished, and at the correct stack depth.
JS_ASSERT(lastIns_);
JS_ASSERT(pred->lastIns_);
JS_ASSERT(stackDepth() == pred->stackDepth());
// We must be a pending loop header
JS_ASSERT(kind_ == PENDING_LOOP_HEADER);
// Add exit definitions to each corresponding phi at the entry.
for (MPhiIterator phi = phisBegin(); phi != phisEnd(); phi++) {
MPhi *entryDef = *phi;
MDefinition *exitDef = pred->getSlot(entryDef->slot());
// Assert that we already placed phis for each slot.
JS_ASSERT(entryDef->block() == this);
// Assert that the phi already has the correct type.
JS_ASSERT(entryDef->type() == exitDef->type());
JS_ASSERT(entryDef->type() != MIRType_Value);
if (entryDef == exitDef) {
// If the exit def is the same as the entry def, make a redundant
// phi. Since loop headers have exactly two incoming edges, we
// know that that's just the first input.
//
// Note that we eliminate later rather than now, to avoid any
// weirdness around pending continue edges which might still hold
// onto phis.
exitDef = entryDef->getOperand(0);
}
// MBasicBlock::NewAsmJS calls reserveLength(2) for loop header phis.
entryDef->addInput(exitDef);
JS_ASSERT(entryDef->slot() < pred->stackDepth());
setSlot(entryDef->slot(), entryDef);
}
// We are now a loop header proper
kind_ = LOOP_HEADER;
return predecessors_.append(pred);
}
bool
TypeAnalyzer::propagateSpecialization(MPhi *phi)
{
JS_ASSERT(phi->type() != MIRType_None);
// Verify that this specialization matches any phis depending on it.
for (MUseDefIterator iter(phi); iter; iter++) {
if (!iter.def()->isPhi())
continue;
MPhi *use = iter.def()->toPhi();
if (!use->triedToSpecialize())
continue;
if (use->type() == MIRType_None) {
// We tried to specialize this phi, but were unable to guess its
// type. Now that we know the type of one of its operands, we can
// specialize it.
if (!respecialize(use, phi->type()))
return false;
continue;
}
if (use->type() != phi->type()) {
// Specialize phis with int32 and double operands as double.
if (IsNumberType(use->type()) && IsNumberType(phi->type())) {
if (!respecialize(use, MIRType_Double))
return false;
continue;
}
// This phi in our use chain can now no longer be specialized.
if (!respecialize(use, MIRType_Value))
return false;
}
}
return true;
}
bool
MBasicBlock::inherit(TempAllocator &alloc, BytecodeAnalysis *analysis, MBasicBlock *pred,
uint32_t popped, unsigned stackPhiCount)
{
if (pred) {
stackPosition_ = pred->stackPosition_;
JS_ASSERT(stackPosition_ >= popped);
stackPosition_ -= popped;
if (kind_ != PENDING_LOOP_HEADER)
copySlots(pred);
} else {
uint32_t stackDepth = analysis->info(pc()).stackDepth;
stackPosition_ = info().firstStackSlot() + stackDepth;
JS_ASSERT(stackPosition_ >= popped);
stackPosition_ -= popped;
}
JS_ASSERT(info_.nslots() >= stackPosition_);
JS_ASSERT(!entryResumePoint_);
// Propagate the caller resume point from the inherited block.
MResumePoint *callerResumePoint = pred ? pred->callerResumePoint() : nullptr;
// Create a resume point using our initial stack state.
entryResumePoint_ = new(alloc) MResumePoint(this, pc(), callerResumePoint, MResumePoint::ResumeAt);
if (!entryResumePoint_->init(alloc))
return false;
if (pred) {
if (!predecessors_.append(pred))
return false;
if (kind_ == PENDING_LOOP_HEADER) {
size_t i = 0;
for (i = 0; i < info().firstStackSlot(); i++) {
MPhi *phi = MPhi::New(alloc, i);
if (!phi->addInputSlow(pred->getSlot(i)))
return false;
addPhi(phi);
setSlot(i, phi);
entryResumePoint()->setOperand(i, phi);
}
JS_ASSERT(stackPhiCount <= stackDepth());
JS_ASSERT(info().firstStackSlot() <= stackDepth() - stackPhiCount);
// Avoid creating new phis for stack values that aren't part of the
// loop. Note that for loop headers that can OSR, all values on the
// stack are part of the loop.
for (; i < stackDepth() - stackPhiCount; i++) {
MDefinition *val = pred->getSlot(i);
setSlot(i, val);
entryResumePoint()->setOperand(i, val);
}
for (; i < stackDepth(); i++) {
MPhi *phi = MPhi::New(alloc, i);
if (!phi->addInputSlow(pred->getSlot(i)))
return false;
addPhi(phi);
setSlot(i, phi);
entryResumePoint()->setOperand(i, phi);
}
} else {
for (size_t i = 0; i < stackDepth(); i++)
entryResumePoint()->setOperand(i, getSlot(i));
}
} else {
/*
* Don't leave the operands uninitialized for the caller, as it may not
* initialize them later on.
*/
for (size_t i = 0; i < stackDepth(); i++)
entryResumePoint()->clearOperand(i);
}
return true;
}
void
LoopUnroller::go(LoopIterationBound *bound)
{
// For now we always unroll loops the same number of times.
static const size_t UnrollCount = 10;
JitSpew(JitSpew_Unrolling, "Attempting to unroll loop");
header = bound->header;
// UCE might have determined this isn't actually a loop.
if (!header->isLoopHeader())
return;
backedge = header->backedge();
oldPreheader = header->loopPredecessor();
JS_ASSERT(oldPreheader->numSuccessors() == 1);
// Only unroll loops with two blocks: an initial one ending with the
// bound's test, and the body ending with the backedge.
MTest *test = bound->test;
if (header->lastIns() != test)
return;
if (test->ifTrue() == backedge) {
if (test->ifFalse()->id() <= backedge->id())
return;
} else if (test->ifFalse() == backedge) {
if (test->ifTrue()->id() <= backedge->id())
return;
} else {
return;
}
if (backedge->numPredecessors() != 1 || backedge->numSuccessors() != 1)
return;
JS_ASSERT(backedge->phisEmpty());
MBasicBlock *bodyBlocks[] = { header, backedge };
// All instructions in the header and body must be clonable.
for (size_t i = 0; i < ArrayLength(bodyBlocks); i++) {
MBasicBlock *block = bodyBlocks[i];
for (MInstructionIterator iter(block->begin()); iter != block->end(); iter++) {
MInstruction *ins = *iter;
if (ins->canClone())
continue;
if (ins->isTest() || ins->isGoto() || ins->isInterruptCheck())
continue;
#ifdef DEBUG
JitSpew(JitSpew_Unrolling, "Aborting: can't clone instruction %s", ins->opName());
#endif
return;
}
}
// Compute the linear inequality we will use for exiting the unrolled loop:
//
// iterationBound - iterationCount - UnrollCount >= 0
//
LinearSum remainingIterationsInequality(bound->boundSum);
if (!remainingIterationsInequality.add(bound->currentSum, -1))
return;
if (!remainingIterationsInequality.add(-int32_t(UnrollCount)))
return;
// Terms in the inequality need to be either loop invariant or phis from
// the original header.
for (size_t i = 0; i < remainingIterationsInequality.numTerms(); i++) {
MDefinition *def = remainingIterationsInequality.term(i).term;
if (def->block()->id() < header->id())
continue;
if (def->block() == header && def->isPhi())
continue;
return;
}
// OK, we've checked everything, now unroll the loop.
JitSpew(JitSpew_Unrolling, "Unrolling loop");
// The old preheader will go before the unrolled loop, and the old loop
// will need a new empty preheader.
CompileInfo &info = oldPreheader->info();
if (header->trackedSite().pc()) {
unrolledHeader =
MBasicBlock::New(graph, nullptr, info,
oldPreheader, header->trackedSite(), MBasicBlock::LOOP_HEADER);
unrolledBackedge =
MBasicBlock::New(graph, nullptr, info,
unrolledHeader, backedge->trackedSite(), MBasicBlock::NORMAL);
newPreheader =
MBasicBlock::New(graph, nullptr, info,
unrolledHeader, oldPreheader->trackedSite(), MBasicBlock::NORMAL);
} else {
unrolledHeader = MBasicBlock::NewAsmJS(graph, info, oldPreheader, MBasicBlock::LOOP_HEADER);
unrolledBackedge = MBasicBlock::NewAsmJS(graph, info, unrolledHeader, MBasicBlock::NORMAL);
newPreheader = MBasicBlock::NewAsmJS(graph, info, unrolledHeader, MBasicBlock::NORMAL);
}
unrolledHeader->discardAllResumePoints();
unrolledBackedge->discardAllResumePoints();
newPreheader->discardAllResumePoints();
// Insert new blocks at their RPO position, and update block ids.
graph.insertBlockAfter(oldPreheader, unrolledHeader);
graph.insertBlockAfter(unrolledHeader, unrolledBackedge);
graph.insertBlockAfter(unrolledBackedge, newPreheader);
graph.renumberBlocksAfter(oldPreheader);
if (!unrolledDefinitions.init())
CrashAtUnhandlableOOM("LoopUnroller::go");
// Add phis to the unrolled loop header which correspond to the phis in the
// original loop header.
JS_ASSERT(header->getPredecessor(0) == oldPreheader);
for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) {
MPhi *old = *iter;
JS_ASSERT(old->numOperands() == 2);
MPhi *phi = MPhi::New(alloc);
phi->setResultType(old->type());
phi->setResultTypeSet(old->resultTypeSet());
phi->setRange(old->range());
unrolledHeader->addPhi(phi);
if (!phi->reserveLength(2))
CrashAtUnhandlableOOM("LoopUnroller::go");
// Set the first input for the phi for now. We'll set the second after
// finishing the unroll.
phi->addInput(old->getOperand(0));
// The old phi will now take the value produced by the unrolled loop.
old->replaceOperand(0, phi);
if (!unrolledDefinitions.putNew(old, phi))
CrashAtUnhandlableOOM("LoopUnroller::go");
}
// The loop condition can bail out on e.g. integer overflow, so make a
// resume point based on the initial resume point of the original header.
MResumePoint *headerResumePoint = header->entryResumePoint();
if (headerResumePoint) {
MResumePoint *rp = makeReplacementResumePoint(unrolledHeader, headerResumePoint);
unrolledHeader->setEntryResumePoint(rp);
// Perform an interrupt check at the start of the unrolled loop.
unrolledHeader->add(MInterruptCheck::New(alloc));
}
// Generate code for the test in the unrolled loop.
for (size_t i = 0; i < remainingIterationsInequality.numTerms(); i++) {
MDefinition *def = remainingIterationsInequality.term(i).term;
MDefinition *replacement = getReplacementDefinition(def);
remainingIterationsInequality.replaceTerm(i, replacement);
}
MCompare *compare = ConvertLinearInequality(alloc, unrolledHeader, remainingIterationsInequality);
MTest *unrolledTest = MTest::New(alloc, compare, unrolledBackedge, newPreheader);
unrolledHeader->end(unrolledTest);
// Make an entry resume point for the unrolled body. The unrolled header
// does not have side effects on stack values, even if the original loop
// header does, so use the same resume point as for the unrolled header.
if (headerResumePoint) {
MResumePoint *rp = makeReplacementResumePoint(unrolledBackedge, headerResumePoint);
unrolledBackedge->setEntryResumePoint(rp);
}
// Make an entry resume point for the new preheader. There are no
// instructions which use this but some other stuff wants one to be here.
if (headerResumePoint) {
MResumePoint *rp = makeReplacementResumePoint(newPreheader, headerResumePoint);
newPreheader->setEntryResumePoint(rp);
}
// Generate the unrolled code.
JS_ASSERT(UnrollCount > 1);
size_t unrollIndex = 0;
while (true) {
// Clone the contents of the original loop into the unrolled loop body.
for (size_t i = 0; i < ArrayLength(bodyBlocks); i++) {
MBasicBlock *block = bodyBlocks[i];
for (MInstructionIterator iter(block->begin()); iter != block->end(); iter++) {
MInstruction *ins = *iter;
if (ins->canClone()) {
makeReplacementInstruction(*iter);
} else {
// Control instructions are handled separately.
JS_ASSERT(ins->isTest() || ins->isGoto() || ins->isInterruptCheck());
}
}
}
// Compute the value of each loop header phi after the execution of
// this unrolled iteration.
MDefinitionVector phiValues(alloc);
JS_ASSERT(header->getPredecessor(1) == backedge);
for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) {
MPhi *old = *iter;
MDefinition *oldInput = old->getOperand(1);
if (!phiValues.append(getReplacementDefinition(oldInput)))
CrashAtUnhandlableOOM("LoopUnroller::go");
}
unrolledDefinitions.clear();
if (unrollIndex == UnrollCount - 1) {
// We're at the end of the last unrolled iteration, set the
// backedge input for the unrolled loop phis.
size_t phiIndex = 0;
for (MPhiIterator iter(unrolledHeader->phisBegin()); iter != unrolledHeader->phisEnd(); iter++) {
MPhi *phi = *iter;
phi->addInput(phiValues[phiIndex++]);
}
JS_ASSERT(phiIndex == phiValues.length());
break;
}
// Update the map for the phis in the next iteration.
size_t phiIndex = 0;
for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) {
MPhi *old = *iter;
if (!unrolledDefinitions.putNew(old, phiValues[phiIndex++]))
CrashAtUnhandlableOOM("LoopUnroller::go");
}
JS_ASSERT(phiIndex == phiValues.length());
unrollIndex++;
}
MGoto *backedgeJump = MGoto::New(alloc, unrolledHeader);
unrolledBackedge->end(backedgeJump);
// Place the old preheader before the unrolled loop.
JS_ASSERT(oldPreheader->lastIns()->isGoto());
oldPreheader->discardLastIns();
oldPreheader->end(MGoto::New(alloc, unrolledHeader));
// Place the new preheader before the original loop.
newPreheader->end(MGoto::New(alloc, header));
// Cleanup the MIR graph.
if (!unrolledHeader->addPredecessorWithoutPhis(unrolledBackedge))
CrashAtUnhandlableOOM("LoopUnroller::go");
header->replacePredecessor(oldPreheader, newPreheader);
oldPreheader->setSuccessorWithPhis(unrolledHeader, 0);
newPreheader->setSuccessorWithPhis(header, 0);
unrolledBackedge->setSuccessorWithPhis(unrolledHeader, 1);
}
MPhi *popPhi() {
MPhi *phi = phiWorklist_.popCopy();
phi->setNotInWorklist();
return phi;
}
