1// Copyright 2014 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/crankshaft/ppc/lithium-gap-resolver-ppc.h"
6
7#include "src/crankshaft/ppc/lithium-codegen-ppc.h"
8
9namespace v8 {
10namespace internal {
11
12static const Register kSavedValueRegister = {11};
13
14LGapResolver::LGapResolver(LCodeGen* owner)
15    : cgen_(owner),
16      moves_(32, owner->zone()),
17      root_index_(0),
18      in_cycle_(false),
19      saved_destination_(NULL) {}
20
21
22void LGapResolver::Resolve(LParallelMove* parallel_move) {
23  DCHECK(moves_.is_empty());
24  // Build up a worklist of moves.
25  BuildInitialMoveList(parallel_move);
26
27  for (int i = 0; i < moves_.length(); ++i) {
28    LMoveOperands move = moves_[i];
29    // Skip constants to perform them last.  They don't block other moves
30    // and skipping such moves with register destinations keeps those
31    // registers free for the whole algorithm.
32    if (!move.IsEliminated() && !move.source()->IsConstantOperand()) {
33      root_index_ = i;  // Any cycle is found when by reaching this move again.
34      PerformMove(i);
35      if (in_cycle_) {
36        RestoreValue();
37      }
38    }
39  }
40
41  // Perform the moves with constant sources.
42  for (int i = 0; i < moves_.length(); ++i) {
43    if (!moves_[i].IsEliminated()) {
44      DCHECK(moves_[i].source()->IsConstantOperand());
45      EmitMove(i);
46    }
47  }
48
49  moves_.Rewind(0);
50}
51
52
53void LGapResolver::BuildInitialMoveList(LParallelMove* parallel_move) {
54  // Perform a linear sweep of the moves to add them to the initial list of
55  // moves to perform, ignoring any move that is redundant (the source is
56  // the same as the destination, the destination is ignored and
57  // unallocated, or the move was already eliminated).
58  const ZoneList<LMoveOperands>* moves = parallel_move->move_operands();
59  for (int i = 0; i < moves->length(); ++i) {
60    LMoveOperands move = moves->at(i);
61    if (!move.IsRedundant()) moves_.Add(move, cgen_->zone());
62  }
63  Verify();
64}
65
66
67void LGapResolver::PerformMove(int index) {
68  // Each call to this function performs a move and deletes it from the move
69  // graph.  We first recursively perform any move blocking this one.  We
70  // mark a move as "pending" on entry to PerformMove in order to detect
71  // cycles in the move graph.
72
73  // We can only find a cycle, when doing a depth-first traversal of moves,
74  // be encountering the starting move again. So by spilling the source of
75  // the starting move, we break the cycle.  All moves are then unblocked,
76  // and the starting move is completed by writing the spilled value to
77  // its destination.  All other moves from the spilled source have been
78  // completed prior to breaking the cycle.
79  // An additional complication is that moves to MemOperands with large
80  // offsets (more than 1K or 4K) require us to spill this spilled value to
81  // the stack, to free up the register.
82  DCHECK(!moves_[index].IsPending());
83  DCHECK(!moves_[index].IsRedundant());
84
85  // Clear this move's destination to indicate a pending move.  The actual
86  // destination is saved in a stack allocated local.  Multiple moves can
87  // be pending because this function is recursive.
88  DCHECK(moves_[index].source() != NULL);  // Or else it will look eliminated.
89  LOperand* destination = moves_[index].destination();
90  moves_[index].set_destination(NULL);
91
92  // Perform a depth-first traversal of the move graph to resolve
93  // dependencies.  Any unperformed, unpending move with a source the same
94  // as this one's destination blocks this one so recursively perform all
95  // such moves.
96  for (int i = 0; i < moves_.length(); ++i) {
97    LMoveOperands other_move = moves_[i];
98    if (other_move.Blocks(destination) && !other_move.IsPending()) {
99      PerformMove(i);
100      // If there is a blocking, pending move it must be moves_[root_index_]
101      // and all other moves with the same source as moves_[root_index_] are
102      // sucessfully executed (because they are cycle-free) by this loop.
103    }
104  }
105
106  // We are about to resolve this move and don't need it marked as
107  // pending, so restore its destination.
108  moves_[index].set_destination(destination);
109
110  // The move may be blocked on a pending move, which must be the starting move.
111  // In this case, we have a cycle, and we save the source of this move to
112  // a scratch register to break it.
113  LMoveOperands other_move = moves_[root_index_];
114  if (other_move.Blocks(destination)) {
115    DCHECK(other_move.IsPending());
116    BreakCycle(index);
117    return;
118  }
119
120  // This move is no longer blocked.
121  EmitMove(index);
122}
123
124
125void LGapResolver::Verify() {
126#ifdef ENABLE_SLOW_DCHECKS
127  // No operand should be the destination for more than one move.
128  for (int i = 0; i < moves_.length(); ++i) {
129    LOperand* destination = moves_[i].destination();
130    for (int j = i + 1; j < moves_.length(); ++j) {
131      SLOW_DCHECK(!destination->Equals(moves_[j].destination()));
132    }
133  }
134#endif
135}
136
137#define __ ACCESS_MASM(cgen_->masm())
138
139void LGapResolver::BreakCycle(int index) {
140  // We save in a register the value that should end up in the source of
141  // moves_[root_index].  After performing all moves in the tree rooted
142  // in that move, we save the value to that source.
143  DCHECK(moves_[index].destination()->Equals(moves_[root_index_].source()));
144  DCHECK(!in_cycle_);
145  in_cycle_ = true;
146  LOperand* source = moves_[index].source();
147  saved_destination_ = moves_[index].destination();
148  if (source->IsRegister()) {
149    __ mr(kSavedValueRegister, cgen_->ToRegister(source));
150  } else if (source->IsStackSlot()) {
151    __ LoadP(kSavedValueRegister, cgen_->ToMemOperand(source));
152  } else if (source->IsDoubleRegister()) {
153    __ fmr(kScratchDoubleReg, cgen_->ToDoubleRegister(source));
154  } else if (source->IsDoubleStackSlot()) {
155    __ lfd(kScratchDoubleReg, cgen_->ToMemOperand(source));
156  } else {
157    UNREACHABLE();
158  }
159  // This move will be done by restoring the saved value to the destination.
160  moves_[index].Eliminate();
161}
162
163
164void LGapResolver::RestoreValue() {
165  DCHECK(in_cycle_);
166  DCHECK(saved_destination_ != NULL);
167
168  // Spilled value is in kSavedValueRegister or kSavedDoubleValueRegister.
169  if (saved_destination_->IsRegister()) {
170    __ mr(cgen_->ToRegister(saved_destination_), kSavedValueRegister);
171  } else if (saved_destination_->IsStackSlot()) {
172    __ StoreP(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_));
173  } else if (saved_destination_->IsDoubleRegister()) {
174    __ fmr(cgen_->ToDoubleRegister(saved_destination_), kScratchDoubleReg);
175  } else if (saved_destination_->IsDoubleStackSlot()) {
176    __ stfd(kScratchDoubleReg, cgen_->ToMemOperand(saved_destination_));
177  } else {
178    UNREACHABLE();
179  }
180
181  in_cycle_ = false;
182  saved_destination_ = NULL;
183}
184
185
186void LGapResolver::EmitMove(int index) {
187  LOperand* source = moves_[index].source();
188  LOperand* destination = moves_[index].destination();
189
190  // Dispatch on the source and destination operand kinds.  Not all
191  // combinations are possible.
192
193  if (source->IsRegister()) {
194    Register source_register = cgen_->ToRegister(source);
195    if (destination->IsRegister()) {
196      __ mr(cgen_->ToRegister(destination), source_register);
197    } else {
198      DCHECK(destination->IsStackSlot());
199      __ StoreP(source_register, cgen_->ToMemOperand(destination));
200    }
201  } else if (source->IsStackSlot()) {
202    MemOperand source_operand = cgen_->ToMemOperand(source);
203    if (destination->IsRegister()) {
204      __ LoadP(cgen_->ToRegister(destination), source_operand);
205    } else {
206      DCHECK(destination->IsStackSlot());
207      MemOperand destination_operand = cgen_->ToMemOperand(destination);
208      if (in_cycle_) {
209        __ LoadP(ip, source_operand);
210        __ StoreP(ip, destination_operand);
211      } else {
212        __ LoadP(kSavedValueRegister, source_operand);
213        __ StoreP(kSavedValueRegister, destination_operand);
214      }
215    }
216
217  } else if (source->IsConstantOperand()) {
218    LConstantOperand* constant_source = LConstantOperand::cast(source);
219    if (destination->IsRegister()) {
220      Register dst = cgen_->ToRegister(destination);
221      if (cgen_->IsInteger32(constant_source)) {
222        cgen_->EmitLoadIntegerConstant(constant_source, dst);
223      } else {
224        __ Move(dst, cgen_->ToHandle(constant_source));
225      }
226    } else if (destination->IsDoubleRegister()) {
227      DoubleRegister result = cgen_->ToDoubleRegister(destination);
228      double v = cgen_->ToDouble(constant_source);
229      __ LoadDoubleLiteral(result, v, ip);
230    } else {
231      DCHECK(destination->IsStackSlot());
232      DCHECK(!in_cycle_);  // Constant moves happen after all cycles are gone.
233      if (cgen_->IsInteger32(constant_source)) {
234        cgen_->EmitLoadIntegerConstant(constant_source, kSavedValueRegister);
235      } else {
236        __ Move(kSavedValueRegister, cgen_->ToHandle(constant_source));
237      }
238      __ StoreP(kSavedValueRegister, cgen_->ToMemOperand(destination));
239    }
240
241  } else if (source->IsDoubleRegister()) {
242    DoubleRegister source_register = cgen_->ToDoubleRegister(source);
243    if (destination->IsDoubleRegister()) {
244      __ fmr(cgen_->ToDoubleRegister(destination), source_register);
245    } else {
246      DCHECK(destination->IsDoubleStackSlot());
247      __ stfd(source_register, cgen_->ToMemOperand(destination));
248    }
249
250  } else if (source->IsDoubleStackSlot()) {
251    MemOperand source_operand = cgen_->ToMemOperand(source);
252    if (destination->IsDoubleRegister()) {
253      __ lfd(cgen_->ToDoubleRegister(destination), source_operand);
254    } else {
255      DCHECK(destination->IsDoubleStackSlot());
256      MemOperand destination_operand = cgen_->ToMemOperand(destination);
257      if (in_cycle_) {
258// kSavedDoubleValueRegister was used to break the cycle,
259// but kSavedValueRegister is free.
260#if V8_TARGET_ARCH_PPC64
261        __ ld(kSavedValueRegister, source_operand);
262        __ std(kSavedValueRegister, destination_operand);
263#else
264        MemOperand source_high_operand = cgen_->ToHighMemOperand(source);
265        MemOperand destination_high_operand =
266            cgen_->ToHighMemOperand(destination);
267        __ lwz(kSavedValueRegister, source_operand);
268        __ stw(kSavedValueRegister, destination_operand);
269        __ lwz(kSavedValueRegister, source_high_operand);
270        __ stw(kSavedValueRegister, destination_high_operand);
271#endif
272      } else {
273        __ lfd(kScratchDoubleReg, source_operand);
274        __ stfd(kScratchDoubleReg, destination_operand);
275      }
276    }
277  } else {
278    UNREACHABLE();
279  }
280
281  moves_[index].Eliminate();
282}
283
284
285#undef __
286}  // namespace internal
287}  // namespace v8
288