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; }