bool
GreedyAllocator::buildPhiMoves(LBlock *block)
{
IonSpew(IonSpew_RegAlloc, " Merging phi state.");
phiMoves = Mover();
MBasicBlock *mblock = block->mir();
if (!mblock->successorWithPhis())
return true;
// Insert moves from our state into our successor's phi.
uint32 pos = mblock->positionInPhiSuccessor();
LBlock *successor = mblock->successorWithPhis()->lir();
for (size_t i = 0; i < successor->numPhis(); i++) {
LPhi *phi = successor->getPhi(i);
JS_ASSERT(phi->numDefs() == 1);
VirtualRegister *phiReg = getVirtualRegister(phi->getDef(0));
allocateStack(phiReg);
LAllocation *in = phi->getOperand(pos);
VirtualRegister *inReg = getVirtualRegister(in->toUse());
allocateStack(inReg);
// Try to get a register for the input.
if (!inReg->hasRegister() && !allocatableRegs().empty(inReg->isDouble())) {
if (!allocateReg(inReg))
return false;
}
// Add a move from the input to the phi.
if (inReg->hasRegister()) {
if (!phiMoves.move(inReg->reg(), phiReg->backingStack()))
return false;
} else {
if (!phiMoves.move(inReg->backingStack(), phiReg->backingStack()))
return false;
}
}
return true;
}
void
GreedyAllocator::informSnapshot(LInstruction *ins)
{
LSnapshot *snapshot = ins->snapshot();
for (size_t i = 0; i < snapshot->numEntries(); i++) {
LAllocation *a = snapshot->getEntry(i);
if (!a->isUse())
continue;
// Every definition in a snapshot gets a stack slot. This
// simplification means we can treat normal snapshots and LOsiPoint
// snapshots (which follow calls) the same, without adding a special
// exception to note that registers are spilled at the LOsiPoint.
VirtualRegister *vr = getVirtualRegister(a->toUse());
allocateStack(vr);
*a = vr->backingStack();
}
}
bool
GreedyAllocator::evict(AnyRegister reg)
{
VirtualRegister *vr = state[reg];
JS_ASSERT(vr->reg() == reg);
// If the virtual register does not have a stack slot, allocate one now.
allocateStack(vr);
// We're allocating bottom-up, so eviction *restores* a register, otherwise
// it could not be used downstream.
if (!restore(vr->backingStack(), reg))
return false;
freeReg(reg);
vr->unsetRegister();
return true;
}
bool
GreedyAllocator::spillDefinition(LDefinition *def)
{
if (def->policy() == LDefinition::PASSTHROUGH)
return true;
VirtualRegister *vr = getVirtualRegister(def);
const LAllocation *output = def->output();
if (output->isRegister()) {
if (vr->hasRegister()) {
// If the returned register is different from the output
// register, a move is required.
AnyRegister out = GetAllocatedRegister(output);
if (out != vr->reg()) {
if (!spill(*output, vr->reg()))
return false;
}
}
// Spill to the stack if needed.
if (vr->hasStackSlot() && vr->backingStackUsed()) {
if (!spill(*output, vr->backingStack()))
return false;
}
} else if (vr->hasRegister()) {
// This definition has a canonical spill location, so make sure to
// load it to the resulting register, if any.
JS_ASSERT(!vr->hasStackSlot());
JS_ASSERT(vr->hasBackingStack());
if (!spill(*output, vr->reg()))
return false;
}
return true;
}
bool
GreedyAllocator::allocateRegisters()
{
// Allocate registers bottom-up, such that we see all uses before their
// definitions.
for (size_t i = graph.numBlocks() - 1; i < graph.numBlocks(); i--) {
LBlock *block = graph.getBlock(i);
IonSpew(IonSpew_RegAlloc, "Allocating block %d", (uint32)i);
// All registers should be free.
JS_ASSERT(state.free == RegisterSet::All());
// Allocate stack for any phis.
for (size_t j = 0; j < block->numPhis(); j++) {
LPhi *phi = block->getPhi(j);
VirtualRegister *vreg = getVirtualRegister(phi->getDef(0));
allocateStack(vreg);
}
// Allocate registers.
if (!allocateRegistersInBlock(block))
return false;
LMoveGroup *entrySpills = block->getEntryMoveGroup();
// We've reached the top of the block. Spill all registers by inserting
// moves from their stack locations.
for (AnyRegisterIterator iter(RegisterSet::All()); iter.more(); iter++) {
VirtualRegister *vreg = state[*iter];
if (!vreg) {
JS_ASSERT(state.free.has(*iter));
continue;
}
JS_ASSERT(vreg->reg() == *iter);
JS_ASSERT(!state.free.has(vreg->reg()));
allocateStack(vreg);
LAllocation *from = LAllocation::New(vreg->backingStack());
LAllocation *to = LAllocation::New(vreg->reg());
if (!entrySpills->add(from, to))
return false;
killReg(vreg);
vreg->unsetRegister();
}
// Before killing phis, ensure that each phi input has its own stack
// allocation. This ensures we won't allocate the same slot for any phi
// as its input, which technically may be legal (since the phi becomes
// the last use of the slot), but we avoid for sanity.
for (size_t i = 0; i < block->numPhis(); i++) {
LPhi *phi = block->getPhi(i);
for (size_t j = 0; j < phi->numOperands(); j++) {
VirtualRegister *in = getVirtualRegister(phi->getOperand(j)->toUse());
allocateStack(in);
}
}
// Kill phis.
for (size_t i = 0; i < block->numPhis(); i++) {
LPhi *phi = block->getPhi(i);
VirtualRegister *vr = getVirtualRegister(phi->getDef(0));
JS_ASSERT(!vr->hasRegister());
killStack(vr);
}
}
return true;
}
