// Copyright 2013 the V8 project authors. All rights reserved. // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // * Redistributions in binary form must reproduce the above // copyright notice, this list of conditions and the following // disclaimer in the documentation and/or other materials provided // with the distribution. // * Neither the name of Google Inc. nor the names of its // contributors may be used to endorse or promote products derived // from this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. #include "v8.h" #include "a64/lithium-gap-resolver-a64.h" #include "a64/lithium-codegen-a64.h" namespace v8 { namespace internal { // We use the root register to spill a value while breaking a cycle in parallel // moves. We don't need access to roots while resolving the move list and using // the root register has two advantages: // - It is not in crankshaft allocatable registers list, so it can't interfere // with any of the moves we are resolving. // - We don't need to push it on the stack, as we can reload it with its value // once we have resolved a cycle. #define kSavedValue root LGapResolver::LGapResolver(LCodeGen* owner) : cgen_(owner), moves_(32, owner->zone()), root_index_(0), in_cycle_(false), saved_destination_(NULL), need_to_restore_root_(false) { } #define __ ACCESS_MASM(cgen_->masm()) void LGapResolver::Resolve(LParallelMove* parallel_move) { ASSERT(moves_.is_empty()); // Build up a worklist of moves. BuildInitialMoveList(parallel_move); for (int i = 0; i < moves_.length(); ++i) { LMoveOperands move = moves_[i]; // Skip constants to perform them last. They don't block other moves // and skipping such moves with register destinations keeps those // registers free for the whole algorithm. if (!move.IsEliminated() && !move.source()->IsConstantOperand()) { root_index_ = i; // Any cycle is found when we reach this move again. PerformMove(i); if (in_cycle_) RestoreValue(); } } // Perform the moves with constant sources. for (int i = 0; i < moves_.length(); ++i) { LMoveOperands move = moves_[i]; if (!move.IsEliminated()) { ASSERT(move.source()->IsConstantOperand()); EmitMove(i); } } if (need_to_restore_root_) { ASSERT(kSavedValue.Is(root)); __ InitializeRootRegister(); need_to_restore_root_ = false; } moves_.Rewind(0); } void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) { // Perform a linear sweep of the moves to add them to the initial list of // moves to perform, ignoring any move that is redundant (the source is // the same as the destination, the destination is ignored and // unallocated, or the move was already eliminated). const ZoneList<LMoveOperands>* moves = parallel_move->move_operands(); for (int i = 0; i < moves->length(); ++i) { LMoveOperands move = moves->at(i); if (!move.IsRedundant()) moves_.Add(move, cgen_->zone()); } Verify(); } void LGapResolver::PerformMove(int index) { // Each call to this function performs a move and deletes it from the move // graph. We first recursively perform any move blocking this one. We // mark a move as "pending" on entry to PerformMove in order to detect // cycles in the move graph. LMoveOperands& current_move = moves_[index]; ASSERT(!current_move.IsPending()); ASSERT(!current_move.IsRedundant()); // Clear this move's destination to indicate a pending move. The actual // destination is saved in a stack allocated local. Multiple moves can // be pending because this function is recursive. ASSERT(current_move.source() != NULL); // Otherwise it will look eliminated. LOperand* destination = current_move.destination(); current_move.set_destination(NULL); // Perform a depth-first traversal of the move graph to resolve // dependencies. Any unperformed, unpending move with a source the same // as this one's destination blocks this one so recursively perform all // such moves. for (int i = 0; i < moves_.length(); ++i) { LMoveOperands other_move = moves_[i]; if (other_move.Blocks(destination) && !other_move.IsPending()) { PerformMove(i); // If there is a blocking, pending move it must be moves_[root_index_] // and all other moves with the same source as moves_[root_index_] are // sucessfully executed (because they are cycle-free) by this loop. } } // We are about to resolve this move and don't need it marked as // pending, so restore its destination. current_move.set_destination(destination); // The move may be blocked on a pending move, which must be the starting move. // In this case, we have a cycle, and we save the source of this move to // a scratch register to break it. LMoveOperands other_move = moves_[root_index_]; if (other_move.Blocks(destination)) { ASSERT(other_move.IsPending()); BreakCycle(index); return; } // This move is no longer blocked. EmitMove(index); } void LGapResolver::Verify() { #ifdef ENABLE_SLOW_ASSERTS // No operand should be the destination for more than one move. for (int i = 0; i < moves_.length(); ++i) { LOperand* destination = moves_[i].destination(); for (int j = i + 1; j < moves_.length(); ++j) { SLOW_ASSERT(!destination->Equals(moves_[j].destination())); } } #endif } void LGapResolver::BreakCycle(int index) { ASSERT(moves_[index].destination()->Equals(moves_[root_index_].source())); ASSERT(!in_cycle_); // We use a register which is not allocatable by crankshaft to break the cycle // to be sure it doesn't interfere with the moves we are resolving. ASSERT(!kSavedValue.IsAllocatable()); need_to_restore_root_ = true; // We save in a register the source of that move and we remember its // destination. Then we mark this move as resolved so the cycle is // broken and we can perform the other moves. in_cycle_ = true; LOperand* source = moves_[index].source(); saved_destination_ = moves_[index].destination(); if (source->IsRegister()) { __ Mov(kSavedValue, cgen_->ToRegister(source)); } else if (source->IsStackSlot()) { __ Ldr(kSavedValue, cgen_->ToMemOperand(source)); } else if (source->IsDoubleRegister()) { // TODO(all): We should use a double register to store the value to avoid // the penalty of the mov across register banks. We are going to reserve // d31 to hold 0.0 value. We could clobber this register while breaking the // cycle and restore it after like we do with the root register. // LGapResolver::RestoreValue() will need to be updated as well when we'll // do that. __ Fmov(kSavedValue, cgen_->ToDoubleRegister(source)); } else if (source->IsDoubleStackSlot()) { __ Ldr(kSavedValue, cgen_->ToMemOperand(source)); } else { UNREACHABLE(); } // Mark this move as resolved. // This move will be actually performed by moving the saved value to this // move's destination in LGapResolver::RestoreValue(). moves_[index].Eliminate(); } void LGapResolver::RestoreValue() { ASSERT(in_cycle_); ASSERT(saved_destination_ != NULL); if (saved_destination_->IsRegister()) { __ Mov(cgen_->ToRegister(saved_destination_), kSavedValue); } else if (saved_destination_->IsStackSlot()) { __ Str(kSavedValue, cgen_->ToMemOperand(saved_destination_)); } else if (saved_destination_->IsDoubleRegister()) { __ Fmov(cgen_->ToDoubleRegister(saved_destination_), kSavedValue); } else if (saved_destination_->IsDoubleStackSlot()) { __ Str(kSavedValue, cgen_->ToMemOperand(saved_destination_)); } else { UNREACHABLE(); } in_cycle_ = false; saved_destination_ = NULL; } void LGapResolver::EmitMove(int index) { LOperand* source = moves_[index].source(); LOperand* destination = moves_[index].destination(); // Dispatch on the source and destination operand kinds. Not all // combinations are possible. if (source->IsRegister()) { Register source_register = cgen_->ToRegister(source); if (destination->IsRegister()) { __ Mov(cgen_->ToRegister(destination), source_register); } else { ASSERT(destination->IsStackSlot()); __ Str(source_register, cgen_->ToMemOperand(destination)); } } else if (source->IsStackSlot()) { MemOperand source_operand = cgen_->ToMemOperand(source); if (destination->IsRegister()) { __ Ldr(cgen_->ToRegister(destination), source_operand); } else { ASSERT(destination->IsStackSlot()); EmitStackSlotMove(index); } } else if (source->IsConstantOperand()) { LConstantOperand* constant_source = LConstantOperand::cast(source); if (destination->IsRegister()) { Register dst = cgen_->ToRegister(destination); if (cgen_->IsSmi(constant_source)) { __ Mov(dst, Operand(cgen_->ToSmi(constant_source))); } else if (cgen_->IsInteger32Constant(constant_source)) { __ Mov(dst, cgen_->ToInteger32(constant_source)); } else { __ LoadObject(dst, cgen_->ToHandle(constant_source)); } } else if (destination->IsDoubleRegister()) { DoubleRegister result = cgen_->ToDoubleRegister(destination); __ Fmov(result, cgen_->ToDouble(constant_source)); } else { ASSERT(destination->IsStackSlot()); ASSERT(!in_cycle_); // Constant moves happen after all cycles are gone. need_to_restore_root_ = true; if (cgen_->IsSmi(constant_source)) { __ Mov(kSavedValue, Operand(cgen_->ToSmi(constant_source))); } else if (cgen_->IsInteger32Constant(constant_source)) { __ Mov(kSavedValue, cgen_->ToInteger32(constant_source)); } else { __ LoadObject(kSavedValue, cgen_->ToHandle(constant_source)); } __ Str(kSavedValue, cgen_->ToMemOperand(destination)); } } else if (source->IsDoubleRegister()) { DoubleRegister src = cgen_->ToDoubleRegister(source); if (destination->IsDoubleRegister()) { __ Fmov(cgen_->ToDoubleRegister(destination), src); } else { ASSERT(destination->IsDoubleStackSlot()); __ Str(src, cgen_->ToMemOperand(destination)); } } else if (source->IsDoubleStackSlot()) { MemOperand src = cgen_->ToMemOperand(source); if (destination->IsDoubleRegister()) { __ Ldr(cgen_->ToDoubleRegister(destination), src); } else { ASSERT(destination->IsDoubleStackSlot()); EmitStackSlotMove(index); } } else { UNREACHABLE(); } // The move has been emitted, we can eliminate it. moves_[index].Eliminate(); } void LGapResolver::EmitStackSlotMove(int index) { // We need a temp register to perform a stack slot to stack slot move, and // the register must not be involved in breaking cycles. // Use the Crankshaft double scratch register as the temporary. DoubleRegister temp = crankshaft_fp_scratch; LOperand* src = moves_[index].source(); LOperand* dst = moves_[index].destination(); ASSERT(src->IsStackSlot()); ASSERT(dst->IsStackSlot()); __ Ldr(temp, cgen_->ToMemOperand(src)); __ Str(temp, cgen_->ToMemOperand(dst)); } } } // namespace v8::internal