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      1 // Copyright 2013 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "src/v8.h"
      6 
      7 #include "src/arm64/delayed-masm-arm64-inl.h"
      8 #include "src/arm64/lithium-codegen-arm64.h"
      9 #include "src/arm64/lithium-gap-resolver-arm64.h"
     10 
     11 namespace v8 {
     12 namespace internal {
     13 
     14 #define __ ACCESS_MASM((&masm_))
     15 
     16 
     17 void DelayedGapMasm::EndDelayedUse() {
     18   DelayedMasm::EndDelayedUse();
     19   if (scratch_register_used()) {
     20     DCHECK(ScratchRegister().Is(root));
     21     DCHECK(!pending());
     22     InitializeRootRegister();
     23     reset_scratch_register_used();
     24   }
     25 }
     26 
     27 
     28 LGapResolver::LGapResolver(LCodeGen* owner)
     29     : cgen_(owner), masm_(owner, owner->masm()), moves_(32, owner->zone()),
     30       root_index_(0), in_cycle_(false), saved_destination_(NULL) {
     31 }
     32 
     33 
     34 void LGapResolver::Resolve(LParallelMove* parallel_move) {
     35   DCHECK(moves_.is_empty());
     36   DCHECK(!masm_.pending());
     37 
     38   // Build up a worklist of moves.
     39   BuildInitialMoveList(parallel_move);
     40 
     41   for (int i = 0; i < moves_.length(); ++i) {
     42     LMoveOperands move = moves_[i];
     43 
     44     // Skip constants to perform them last. They don't block other moves
     45     // and skipping such moves with register destinations keeps those
     46     // registers free for the whole algorithm.
     47     if (!move.IsEliminated() && !move.source()->IsConstantOperand()) {
     48       root_index_ = i;  // Any cycle is found when we reach this move again.
     49       PerformMove(i);
     50       if (in_cycle_) RestoreValue();
     51     }
     52   }
     53 
     54   // Perform the moves with constant sources.
     55   for (int i = 0; i < moves_.length(); ++i) {
     56     LMoveOperands move = moves_[i];
     57 
     58     if (!move.IsEliminated()) {
     59       DCHECK(move.source()->IsConstantOperand());
     60       EmitMove(i);
     61     }
     62   }
     63 
     64   __ EndDelayedUse();
     65 
     66   moves_.Rewind(0);
     67 }
     68 
     69 
     70 void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) {
     71   // Perform a linear sweep of the moves to add them to the initial list of
     72   // moves to perform, ignoring any move that is redundant (the source is
     73   // the same as the destination, the destination is ignored and
     74   // unallocated, or the move was already eliminated).
     75   const ZoneList<LMoveOperands>* moves = parallel_move->move_operands();
     76   for (int i = 0; i < moves->length(); ++i) {
     77     LMoveOperands move = moves->at(i);
     78     if (!move.IsRedundant()) moves_.Add(move, cgen_->zone());
     79   }
     80   Verify();
     81 }
     82 
     83 
     84 void LGapResolver::PerformMove(int index) {
     85   // Each call to this function performs a move and deletes it from the move
     86   // graph. We first recursively perform any move blocking this one. We
     87   // mark a move as "pending" on entry to PerformMove in order to detect
     88   // cycles in the move graph.
     89   LMoveOperands& current_move = moves_[index];
     90 
     91   DCHECK(!current_move.IsPending());
     92   DCHECK(!current_move.IsRedundant());
     93 
     94   // Clear this move's destination to indicate a pending move.  The actual
     95   // destination is saved in a stack allocated local. Multiple moves can
     96   // be pending because this function is recursive.
     97   DCHECK(current_move.source() != NULL);  // Otherwise it will look eliminated.
     98   LOperand* destination = current_move.destination();
     99   current_move.set_destination(NULL);
    100 
    101   // Perform a depth-first traversal of the move graph to resolve
    102   // dependencies. Any unperformed, unpending move with a source the same
    103   // as this one's destination blocks this one so recursively perform all
    104   // such moves.
    105   for (int i = 0; i < moves_.length(); ++i) {
    106     LMoveOperands other_move = moves_[i];
    107     if (other_move.Blocks(destination) && !other_move.IsPending()) {
    108       PerformMove(i);
    109       // If there is a blocking, pending move it must be moves_[root_index_]
    110       // and all other moves with the same source as moves_[root_index_] are
    111       // sucessfully executed (because they are cycle-free) by this loop.
    112     }
    113   }
    114 
    115   // We are about to resolve this move and don't need it marked as
    116   // pending, so restore its destination.
    117   current_move.set_destination(destination);
    118 
    119   // The move may be blocked on a pending move, which must be the starting move.
    120   // In this case, we have a cycle, and we save the source of this move to
    121   // a scratch register to break it.
    122   LMoveOperands other_move = moves_[root_index_];
    123   if (other_move.Blocks(destination)) {
    124     DCHECK(other_move.IsPending());
    125     BreakCycle(index);
    126     return;
    127   }
    128 
    129   // This move is no longer blocked.
    130   EmitMove(index);
    131 }
    132 
    133 
    134 void LGapResolver::Verify() {
    135 #ifdef ENABLE_SLOW_DCHECKS
    136   // No operand should be the destination for more than one move.
    137   for (int i = 0; i < moves_.length(); ++i) {
    138     LOperand* destination = moves_[i].destination();
    139     for (int j = i + 1; j < moves_.length(); ++j) {
    140       SLOW_DCHECK(!destination->Equals(moves_[j].destination()));
    141     }
    142   }
    143 #endif
    144 }
    145 
    146 
    147 void LGapResolver::BreakCycle(int index) {
    148   DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source()));
    149   DCHECK(!in_cycle_);
    150 
    151   // We save in a register the source of that move and we remember its
    152   // destination. Then we mark this move as resolved so the cycle is
    153   // broken and we can perform the other moves.
    154   in_cycle_ = true;
    155   LOperand* source = moves_[index].source();
    156   saved_destination_ = moves_[index].destination();
    157 
    158   if (source->IsRegister()) {
    159     AcquireSavedValueRegister();
    160     __ Mov(SavedValueRegister(), cgen_->ToRegister(source));
    161   } else if (source->IsStackSlot()) {
    162     AcquireSavedValueRegister();
    163     __ Load(SavedValueRegister(), cgen_->ToMemOperand(source));
    164   } else if (source->IsDoubleRegister()) {
    165     __ Fmov(SavedFPValueRegister(), cgen_->ToDoubleRegister(source));
    166   } else if (source->IsDoubleStackSlot()) {
    167     __ Load(SavedFPValueRegister(), cgen_->ToMemOperand(source));
    168   } else {
    169     UNREACHABLE();
    170   }
    171 
    172   // Mark this move as resolved.
    173   // This move will be actually performed by moving the saved value to this
    174   // move's destination in LGapResolver::RestoreValue().
    175   moves_[index].Eliminate();
    176 }
    177 
    178 
    179 void LGapResolver::RestoreValue() {
    180   DCHECK(in_cycle_);
    181   DCHECK(saved_destination_ != NULL);
    182 
    183   if (saved_destination_->IsRegister()) {
    184     __ Mov(cgen_->ToRegister(saved_destination_), SavedValueRegister());
    185     ReleaseSavedValueRegister();
    186   } else if (saved_destination_->IsStackSlot()) {
    187     __ Store(SavedValueRegister(), cgen_->ToMemOperand(saved_destination_));
    188     ReleaseSavedValueRegister();
    189   } else if (saved_destination_->IsDoubleRegister()) {
    190     __ Fmov(cgen_->ToDoubleRegister(saved_destination_),
    191             SavedFPValueRegister());
    192   } else if (saved_destination_->IsDoubleStackSlot()) {
    193     __ Store(SavedFPValueRegister(), cgen_->ToMemOperand(saved_destination_));
    194   } else {
    195     UNREACHABLE();
    196   }
    197 
    198   in_cycle_ = false;
    199   saved_destination_ = NULL;
    200 }
    201 
    202 
    203 void LGapResolver::EmitMove(int index) {
    204   LOperand* source = moves_[index].source();
    205   LOperand* destination = moves_[index].destination();
    206 
    207   // Dispatch on the source and destination operand kinds.  Not all
    208   // combinations are possible.
    209 
    210   if (source->IsRegister()) {
    211     Register source_register = cgen_->ToRegister(source);
    212     if (destination->IsRegister()) {
    213       __ Mov(cgen_->ToRegister(destination), source_register);
    214     } else {
    215       DCHECK(destination->IsStackSlot());
    216       __ Store(source_register, cgen_->ToMemOperand(destination));
    217     }
    218 
    219   } else if (source->IsStackSlot()) {
    220     MemOperand source_operand = cgen_->ToMemOperand(source);
    221     if (destination->IsRegister()) {
    222       __ Load(cgen_->ToRegister(destination), source_operand);
    223     } else {
    224       DCHECK(destination->IsStackSlot());
    225       EmitStackSlotMove(index);
    226     }
    227 
    228   } else if (source->IsConstantOperand()) {
    229     LConstantOperand* constant_source = LConstantOperand::cast(source);
    230     if (destination->IsRegister()) {
    231       Register dst = cgen_->ToRegister(destination);
    232       if (cgen_->IsSmi(constant_source)) {
    233         __ Mov(dst, cgen_->ToSmi(constant_source));
    234       } else if (cgen_->IsInteger32Constant(constant_source)) {
    235         __ Mov(dst, cgen_->ToInteger32(constant_source));
    236       } else {
    237         __ LoadObject(dst, cgen_->ToHandle(constant_source));
    238       }
    239     } else if (destination->IsDoubleRegister()) {
    240       DoubleRegister result = cgen_->ToDoubleRegister(destination);
    241       __ Fmov(result, cgen_->ToDouble(constant_source));
    242     } else {
    243       DCHECK(destination->IsStackSlot());
    244       DCHECK(!in_cycle_);  // Constant moves happen after all cycles are gone.
    245       if (cgen_->IsSmi(constant_source)) {
    246         Smi* smi = cgen_->ToSmi(constant_source);
    247         __ StoreConstant(reinterpret_cast<intptr_t>(smi),
    248                          cgen_->ToMemOperand(destination));
    249       } else if (cgen_->IsInteger32Constant(constant_source)) {
    250         __ StoreConstant(cgen_->ToInteger32(constant_source),
    251                          cgen_->ToMemOperand(destination));
    252       } else {
    253         Handle<Object> handle = cgen_->ToHandle(constant_source);
    254         AllowDeferredHandleDereference smi_object_check;
    255         if (handle->IsSmi()) {
    256           Object* obj = *handle;
    257           DCHECK(!obj->IsHeapObject());
    258           __ StoreConstant(reinterpret_cast<intptr_t>(obj),
    259                            cgen_->ToMemOperand(destination));
    260         } else {
    261           AcquireSavedValueRegister();
    262           __ LoadObject(SavedValueRegister(), handle);
    263           __ Store(SavedValueRegister(), cgen_->ToMemOperand(destination));
    264           ReleaseSavedValueRegister();
    265         }
    266       }
    267     }
    268 
    269   } else if (source->IsDoubleRegister()) {
    270     DoubleRegister src = cgen_->ToDoubleRegister(source);
    271     if (destination->IsDoubleRegister()) {
    272       __ Fmov(cgen_->ToDoubleRegister(destination), src);
    273     } else {
    274       DCHECK(destination->IsDoubleStackSlot());
    275       __ Store(src, cgen_->ToMemOperand(destination));
    276     }
    277 
    278   } else if (source->IsDoubleStackSlot()) {
    279     MemOperand src = cgen_->ToMemOperand(source);
    280     if (destination->IsDoubleRegister()) {
    281       __ Load(cgen_->ToDoubleRegister(destination), src);
    282     } else {
    283       DCHECK(destination->IsDoubleStackSlot());
    284       EmitStackSlotMove(index);
    285     }
    286 
    287   } else {
    288     UNREACHABLE();
    289   }
    290 
    291   // The move has been emitted, we can eliminate it.
    292   moves_[index].Eliminate();
    293 }
    294 
    295 } }  // namespace v8::internal
    296