// Copyright 2012 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 "arm/lithium-gap-resolver-arm.h" #include "arm/lithium-codegen-arm.h" namespace v8 { namespace internal { static const Register kSavedValueRegister = { 9 }; LGapResolver::LGapResolver(LCodeGen* owner) : cgen_(owner), moves_(32, owner->zone()), root_index_(0), in_cycle_(false), saved_destination_(NULL) { } 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 by reaching this move again. PerformMove(i); if (in_cycle_) { RestoreValue(); } } } // Perform the moves with constant sources. for (int i = 0; i < moves_.length(); ++i) { if (!moves_[i].IsEliminated()) { ASSERT(moves_[i].source()->IsConstantOperand()); EmitMove(i); } } 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. // We can only find a cycle, when doing a depth-first traversal of moves, // be encountering the starting move again. So by spilling the source of // the starting move, we break the cycle. All moves are then unblocked, // and the starting move is completed by writing the spilled value to // its destination. All other moves from the spilled source have been // completed prior to breaking the cycle. // An additional complication is that moves to MemOperands with large // offsets (more than 1K or 4K) require us to spill this spilled value to // the stack, to free up the register. ASSERT(!moves_[index].IsPending()); ASSERT(!moves_[index].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(moves_[index].source() != NULL); // Or else it will look eliminated. LOperand* destination = moves_[index].destination(); moves_[index].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. moves_[index].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 } #define __ ACCESS_MASM(cgen_->masm()) void LGapResolver::BreakCycle(int index) { // We save in a register the value that should end up in the source of // moves_[root_index]. After performing all moves in the tree rooted // in that move, we save the value to that source. ASSERT(moves_[index].destination()->Equals(moves_[root_index_].source())); ASSERT(!in_cycle_); in_cycle_ = true; LOperand* source = moves_[index].source(); saved_destination_ = moves_[index].destination(); if (source->IsRegister()) { __ mov(kSavedValueRegister, cgen_->ToRegister(source)); } else if (source->IsStackSlot()) { __ ldr(kSavedValueRegister, cgen_->ToMemOperand(source)); } else if (source->IsDoubleRegister()) { __ vmov(kScratchDoubleReg, cgen_->ToDoubleRegister(source)); } else if (source->IsDoubleStackSlot()) { __ vldr(kScratchDoubleReg, cgen_->ToMemOperand(source)); } else { UNREACHABLE(); } // This move will be done by restoring the saved value to the destination. moves_[index].Eliminate(); } void LGapResolver::RestoreValue() { ASSERT(in_cycle_); ASSERT(saved_destination_ != NULL); // Spilled value is in kSavedValueRegister or kSavedDoubleValueRegister. if (saved_destination_->IsRegister()) { __ mov(cgen_->ToRegister(saved_destination_), kSavedValueRegister); } else if (saved_destination_->IsStackSlot()) { __ str(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_)); } else if (saved_destination_->IsDoubleRegister()) { __ vmov(cgen_->ToDoubleRegister(saved_destination_), kScratchDoubleReg); } else if (saved_destination_->IsDoubleStackSlot()) { __ vstr(kScratchDoubleReg, 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()); MemOperand destination_operand = cgen_->ToMemOperand(destination); if (in_cycle_) { if (!destination_operand.OffsetIsUint12Encodable()) { // ip is overwritten while saving the value to the destination. // Therefore we can't use ip. It is OK if the read from the source // destroys ip, since that happens before the value is read. __ vldr(kScratchDoubleReg.low(), source_operand); __ vstr(kScratchDoubleReg.low(), destination_operand); } else { __ ldr(ip, source_operand); __ str(ip, destination_operand); } } else { __ ldr(kSavedValueRegister, source_operand); __ str(kSavedValueRegister, destination_operand); } } } else if (source->IsConstantOperand()) { LConstantOperand* constant_source = LConstantOperand::cast(source); if (destination->IsRegister()) { Register dst = cgen_->ToRegister(destination); Representation r = cgen_->IsSmi(constant_source) ? Representation::Smi() : Representation::Integer32(); if (cgen_->IsInteger32(constant_source)) { __ mov(dst, Operand(cgen_->ToRepresentation(constant_source, r))); } else { __ Move(dst, cgen_->ToHandle(constant_source)); } } else if (destination->IsDoubleRegister()) { DwVfpRegister result = cgen_->ToDoubleRegister(destination); double v = cgen_->ToDouble(constant_source); __ Vmov(result, v, ip); } else { ASSERT(destination->IsStackSlot()); ASSERT(!in_cycle_); // Constant moves happen after all cycles are gone. Representation r = cgen_->IsSmi(constant_source) ? Representation::Smi() : Representation::Integer32(); if (cgen_->IsInteger32(constant_source)) { __ mov(kSavedValueRegister, Operand(cgen_->ToRepresentation(constant_source, r))); } else { __ Move(kSavedValueRegister, cgen_->ToHandle(constant_source)); } __ str(kSavedValueRegister, cgen_->ToMemOperand(destination)); } } else if (source->IsDoubleRegister()) { DwVfpRegister source_register = cgen_->ToDoubleRegister(source); if (destination->IsDoubleRegister()) { __ vmov(cgen_->ToDoubleRegister(destination), source_register); } else { ASSERT(destination->IsDoubleStackSlot()); __ vstr(source_register, cgen_->ToMemOperand(destination)); } } else if (source->IsDoubleStackSlot()) { MemOperand source_operand = cgen_->ToMemOperand(source); if (destination->IsDoubleRegister()) { __ vldr(cgen_->ToDoubleRegister(destination), source_operand); } else { ASSERT(destination->IsDoubleStackSlot()); MemOperand destination_operand = cgen_->ToMemOperand(destination); if (in_cycle_) { // kSavedDoubleValueRegister was used to break the cycle, // but kSavedValueRegister is free. MemOperand source_high_operand = cgen_->ToHighMemOperand(source); MemOperand destination_high_operand = cgen_->ToHighMemOperand(destination); __ ldr(kSavedValueRegister, source_operand); __ str(kSavedValueRegister, destination_operand); __ ldr(kSavedValueRegister, source_high_operand); __ str(kSavedValueRegister, destination_high_operand); } else { __ vldr(kScratchDoubleReg, source_operand); __ vstr(kScratchDoubleReg, destination_operand); } } } else { UNREACHABLE(); } moves_[index].Eliminate(); } #undef __ } } // namespace v8::internal