ARM: Port new version of ParallelMove's GapResolver to ARM. Fix error in...

ARM: Port new version of ParallelMove's GapResolver to ARM.  Fix error in vstr(DoubleRegister, MemOperand), where it was implemented as a vldr, in r6830.
Review URL: http://codereview.chromium.org/6311010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6839 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/SConscript

@@ -153,6 +153,7 @@ SOURCES = {
     arm/jump-target-arm.cc
     arm/lithium-arm.cc
     arm/lithium-codegen-arm.cc
+    arm/lithium-gap-resolver-arm.cc
     arm/macro-assembler-arm.cc
     arm/regexp-macro-assembler-arm.cc
     arm/register-allocator-arm.cc

src/arm/assembler-arm.cc

@@ -1957,7 +1957,7 @@ void Assembler::vstr(const DwVfpRegister src,
                      const Condition cond) {
   ASSERT(!operand.rm().is_valid());
   ASSERT(operand.am_ == Offset);
-  vldr(src, operand.rn(), operand.offset(), cond);
+  vstr(src, operand.rn(), operand.offset(), cond);
 }
 
 

src/arm/lithium-codegen-arm.cc

@@ -26,6 +26,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "arm/lithium-codegen-arm.h"
+#include "arm/lithium-gap-resolver-arm.h"
 #include "code-stubs.h"
 #include "stub-cache.h"
 
@@ -54,157 +55,6 @@ class SafepointGenerator : public PostCallGenerator {
 };
 
 
-class LGapNode: public ZoneObject {
- public:
-  explicit LGapNode(LOperand* operand)
-      : operand_(operand), resolved_(false), visited_id_(-1) { }
-
-  LOperand* operand() const { return operand_; }
-  bool IsResolved() const { return !IsAssigned() || resolved_; }
-  void MarkResolved() {
-    ASSERT(!IsResolved());
-    resolved_ = true;
-  }
-  int visited_id() const { return visited_id_; }
-  void set_visited_id(int id) {
-    ASSERT(id > visited_id_);
-    visited_id_ = id;
-  }
-
-  bool IsAssigned() const { return assigned_from_.is_set(); }
-  LGapNode* assigned_from() const { return assigned_from_.get(); }
-  void set_assigned_from(LGapNode* n) { assigned_from_.set(n); }
-
- private:
-  LOperand* operand_;
-  SetOncePointer<LGapNode> assigned_from_;
-  bool resolved_;
-  int visited_id_;
-};
-
-
-LGapResolver::LGapResolver()
-    : nodes_(32),
-      identified_cycles_(4),
-      result_(16),
-      next_visited_id_(0) {
-}
-
-
-const ZoneList<LMoveOperands>* LGapResolver::Resolve(
-    const ZoneList<LMoveOperands>* moves,
-    LOperand* marker_operand) {
-  nodes_.Rewind(0);
-  identified_cycles_.Rewind(0);
-  result_.Rewind(0);
-  next_visited_id_ = 0;
-
-  for (int i = 0; i < moves->length(); ++i) {
-    LMoveOperands move = moves->at(i);
-    if (!move.IsRedundant()) RegisterMove(move);
-  }
-
-  for (int i = 0; i < identified_cycles_.length(); ++i) {
-    ResolveCycle(identified_cycles_[i], marker_operand);
-  }
-
-  int unresolved_nodes;
-  do {
-    unresolved_nodes = 0;
-    for (int j = 0; j < nodes_.length(); j++) {
-      LGapNode* node = nodes_[j];
-      if (!node->IsResolved() && node->assigned_from()->IsResolved()) {
-        AddResultMove(node->assigned_from(), node);
-        node->MarkResolved();
-      }
-      if (!node->IsResolved()) ++unresolved_nodes;
-    }
-  } while (unresolved_nodes > 0);
-  return &result_;
-}
-
-
-void LGapResolver::AddResultMove(LGapNode* from, LGapNode* to) {
-  AddResultMove(from->operand(), to->operand());
-}
-
-
-void LGapResolver::AddResultMove(LOperand* from, LOperand* to) {
-  result_.Add(LMoveOperands(from, to));
-}
-
-
-void LGapResolver::ResolveCycle(LGapNode* start, LOperand* marker_operand) {
-  ZoneList<LOperand*> cycle_operands(8);
-  cycle_operands.Add(marker_operand);
-  LGapNode* cur = start;
-  do {
-    cur->MarkResolved();
-    cycle_operands.Add(cur->operand());
-    cur = cur->assigned_from();
-  } while (cur != start);
-  cycle_operands.Add(marker_operand);
-
-  for (int i = cycle_operands.length() - 1; i > 0; --i) {
-    LOperand* from = cycle_operands[i];
-    LOperand* to = cycle_operands[i - 1];
-    AddResultMove(from, to);
-  }
-}
-
-
-bool LGapResolver::CanReach(LGapNode* a, LGapNode* b, int visited_id) {
-  ASSERT(a != b);
-  LGapNode* cur = a;
-  while (cur != b && cur->visited_id() != visited_id && cur->IsAssigned()) {
-    cur->set_visited_id(visited_id);
-    cur = cur->assigned_from();
-  }
-
-  return cur == b;
-}
-
-
-bool LGapResolver::CanReach(LGapNode* a, LGapNode* b) {
-  ASSERT(a != b);
-  return CanReach(a, b, next_visited_id_++);
-}
-
-
-void LGapResolver::RegisterMove(LMoveOperands move) {
-  if (move.source()->IsConstantOperand()) {
-    // Constant moves should be last in the machine code. Therefore add them
-    // first to the result set.
-    AddResultMove(move.source(), move.destination());
-  } else {
-    LGapNode* from = LookupNode(move.source());
-    LGapNode* to = LookupNode(move.destination());
-    if (to->IsAssigned() && to->assigned_from() == from) {
-      move.Eliminate();
-      return;
-    }
-    ASSERT(!to->IsAssigned());
-    if (CanReach(from, to)) {
-      // This introduces a cycle. Save.
-      identified_cycles_.Add(from);
-    }
-    to->set_assigned_from(from);
-  }
-}
-
-
-LGapNode* LGapResolver::LookupNode(LOperand* operand) {
-  for (int i = 0; i < nodes_.length(); ++i) {
-    if (nodes_[i]->operand()->Equals(operand)) return nodes_[i];
-  }
-
-  // No node found => create a new one.
-  LGapNode* result = new LGapNode(operand);
-  nodes_.Add(result);
-  return result;
-}
-
-
 #define __ masm()->
 
 bool LCodeGen::GenerateCode() {
@@ -464,7 +314,6 @@ Operand LCodeGen::ToOperand(LOperand* op) {
 
 
 MemOperand LCodeGen::ToMemOperand(LOperand* op) const {
-  // TODO(regis): Revisit.
   ASSERT(!op->IsRegister());
   ASSERT(!op->IsDoubleRegister());
   ASSERT(op->IsStackSlot() || op->IsDoubleStackSlot());
@@ -480,6 +329,21 @@ MemOperand LCodeGen::ToMemOperand(LOperand* op) const {
 }
 
 
+MemOperand LCodeGen::ToHighMemOperand(LOperand* op) const {
+  ASSERT(op->IsDoubleStackSlot());
+  int index = op->index();
+  if (index >= 0) {
+    // Local or spill slot. Skip the frame pointer, function, context,
+    // and the first word of the double in the fixed part of the frame.
+    return MemOperand(fp, -(index + 3) * kPointerSize + kPointerSize);
+  } else {
+    // Incoming parameter. Skip the return address and the first word of
+    // the double.
+    return MemOperand(fp, -(index - 1) * kPointerSize + kPointerSize);
+  }
+}
+
+
 void LCodeGen::WriteTranslation(LEnvironment* environment,
                                 Translation* translation) {
   if (environment == NULL) return;
@@ -787,116 +651,7 @@ void LCodeGen::DoLabel(LLabel* label) {
 
 
 void LCodeGen::DoParallelMove(LParallelMove* move) {
-  // d0 must always be a scratch register.
-  DoubleRegister dbl_scratch = d0;
-  LUnallocated marker_operand(LUnallocated::NONE);
-
-  Register core_scratch = scratch0();
-  bool destroys_core_scratch = false;
-
-  const ZoneList<LMoveOperands>* moves =
-      resolver_.Resolve(move->move_operands(), &marker_operand);
-  for (int i = moves->length() - 1; i >= 0; --i) {
-    LMoveOperands move = moves->at(i);
-    LOperand* from = move.source();
-    LOperand* to = move.destination();
-    ASSERT(!from->IsDoubleRegister() ||
-           !ToDoubleRegister(from).is(dbl_scratch));
-    ASSERT(!to->IsDoubleRegister() || !ToDoubleRegister(to).is(dbl_scratch));
-    ASSERT(!from->IsRegister() || !ToRegister(from).is(core_scratch));
-    ASSERT(!to->IsRegister() || !ToRegister(to).is(core_scratch));
-    if (from == &marker_operand) {
-      if (to->IsRegister()) {
-        __ mov(ToRegister(to), core_scratch);
-        ASSERT(destroys_core_scratch);
-      } else if (to->IsStackSlot()) {
-        __ str(core_scratch, ToMemOperand(to));
-        ASSERT(destroys_core_scratch);
-      } else if (to->IsDoubleRegister()) {
-        __ vmov(ToDoubleRegister(to), dbl_scratch);
-      } else {
-        ASSERT(to->IsDoubleStackSlot());
-        // TODO(regis): Why is vstr not taking a MemOperand?
-        // __ vstr(dbl_scratch, ToMemOperand(to));
-        MemOperand to_operand = ToMemOperand(to);
-        __ vstr(dbl_scratch, to_operand.rn(), to_operand.offset());
-      }
-    } else if (to == &marker_operand) {
-      if (from->IsRegister() || from->IsConstantOperand()) {
-        __ mov(core_scratch, ToOperand(from));
-        destroys_core_scratch = true;
-      } else if (from->IsStackSlot()) {
-        __ ldr(core_scratch, ToMemOperand(from));
-        destroys_core_scratch = true;
-      } else if (from->IsDoubleRegister()) {
-        __ vmov(dbl_scratch, ToDoubleRegister(from));
-      } else {
-        ASSERT(from->IsDoubleStackSlot());
-        // TODO(regis): Why is vldr not taking a MemOperand?
-        // __ vldr(dbl_scratch, ToMemOperand(from));
-        MemOperand from_operand = ToMemOperand(from);
-        __ vldr(dbl_scratch, from_operand.rn(), from_operand.offset());
-      }
-    } else if (from->IsConstantOperand()) {
-      if (to->IsRegister()) {
-        __ mov(ToRegister(to), ToOperand(from));
-      } else {
-        ASSERT(to->IsStackSlot());
-        __ mov(ip, ToOperand(from));
-        __ str(ip, ToMemOperand(to));
-      }
-    } else if (from->IsRegister()) {
-      if (to->IsRegister()) {
-        __ mov(ToRegister(to), ToOperand(from));
-      } else {
-        ASSERT(to->IsStackSlot());
-        __ str(ToRegister(from), ToMemOperand(to));
-      }
-    } else if (to->IsRegister()) {
-      ASSERT(from->IsStackSlot());
-      __ ldr(ToRegister(to), ToMemOperand(from));
-    } else if (from->IsStackSlot()) {
-      ASSERT(to->IsStackSlot());
-      __ ldr(ip, ToMemOperand(from));
-      __ str(ip, ToMemOperand(to));
-    } else if (from->IsDoubleRegister()) {
-      if (to->IsDoubleRegister()) {
-      __ vmov(ToDoubleRegister(to), ToDoubleRegister(from));
-      } else {
-        ASSERT(to->IsDoubleStackSlot());
-        // TODO(regis): Why is vstr not taking a MemOperand?
-        // __ vstr(dbl_scratch, ToMemOperand(to));
-        MemOperand to_operand = ToMemOperand(to);
-        __ vstr(ToDoubleRegister(from), to_operand.rn(), to_operand.offset());
-      }
-    } else if (to->IsDoubleRegister()) {
-      ASSERT(from->IsDoubleStackSlot());
-      // TODO(regis): Why is vldr not taking a MemOperand?
-      // __ vldr(ToDoubleRegister(to), ToMemOperand(from));
-      MemOperand from_operand = ToMemOperand(from);
-      __ vldr(ToDoubleRegister(to), from_operand.rn(), from_operand.offset());
-    } else {
-      ASSERT(to->IsDoubleStackSlot() && from->IsDoubleStackSlot());
-      // TODO(regis): Why is vldr not taking a MemOperand?
-      // __ vldr(dbl_scratch, ToMemOperand(from));
-      MemOperand from_operand = ToMemOperand(from);
-      __ vldr(dbl_scratch, from_operand.rn(), from_operand.offset());
-      // TODO(regis): Why is vstr not taking a MemOperand?
-      // __ vstr(dbl_scratch, ToMemOperand(to));
-      MemOperand to_operand = ToMemOperand(to);
-      __ vstr(dbl_scratch, to_operand.rn(), to_operand.offset());
-    }
-  }
-
-  if (destroys_core_scratch) {
-    __ ldr(core_scratch, MemOperand(fp, -kPointerSize));
-  }
-
-  LInstruction* next = GetNextInstruction();
-  if (next != NULL && next->IsLazyBailout()) {
-    int pc = masm()->pc_offset();
-    safepoints_.SetPcAfterGap(pc);
-  }
+  resolver_.Resolve(move);
 }
 
 

src/arm/lithium-codegen-arm.h

@@ -29,7 +29,7 @@
 #define V8_ARM_LITHIUM_CODEGEN_ARM_H_
 
 #include "arm/lithium-arm.h"
-
+#include "arm/lithium-gap-resolver-arm.h"
 #include "deoptimizer.h"
 #include "safepoint-table.h"
 #include "scopes.h"
@@ -39,31 +39,8 @@ namespace internal {
 
 // Forward declarations.
 class LDeferredCode;
-class LGapNode;
 class SafepointGenerator;
 
-class LGapResolver BASE_EMBEDDED {
- public:
-  LGapResolver();
-  const ZoneList<LMoveOperands>* Resolve(const ZoneList<LMoveOperands>* moves,
-                                         LOperand* marker_operand);
-
- private:
-  LGapNode* LookupNode(LOperand* operand);
-  bool CanReach(LGapNode* a, LGapNode* b, int visited_id);
-  bool CanReach(LGapNode* a, LGapNode* b);
-  void RegisterMove(LMoveOperands move);
-  void AddResultMove(LOperand* from, LOperand* to);
-  void AddResultMove(LGapNode* from, LGapNode* to);
-  void ResolveCycle(LGapNode* start, LOperand* marker_operand);
-
-  ZoneList<LGapNode*> nodes_;
-  ZoneList<LGapNode*> identified_cycles_;
-  ZoneList<LMoveOperands> result_;
-  int next_visited_id_;
-};
-
-
 class LCodeGen BASE_EMBEDDED {
  public:
   LCodeGen(LChunk* chunk, MacroAssembler* assembler, CompilationInfo* info)
@@ -79,10 +56,35 @@ class LCodeGen BASE_EMBEDDED {
         scope_(chunk->graph()->info()->scope()),
         status_(UNUSED),
         deferred_(8),
-        osr_pc_offset_(-1) {
+        osr_pc_offset_(-1),
+        resolver_(this) {
     PopulateDeoptimizationLiteralsWithInlinedFunctions();
   }
 
+
+  // Simple accessors.
+  MacroAssembler* masm() const { return masm_; }
+
+  // Support for converting LOperands to assembler types.
+  // LOperand must be a register.
+  Register ToRegister(LOperand* op) const;
+
+  // LOperand is loaded into scratch, unless already a register.
+  Register EmitLoadRegister(LOperand* op, Register scratch);
+
+  // LOperand must be a double register.
+  DoubleRegister ToDoubleRegister(LOperand* op) const;
+
+  // LOperand is loaded into dbl_scratch, unless already a double register.
+  DoubleRegister EmitLoadDoubleRegister(LOperand* op,
+                                        SwVfpRegister flt_scratch,
+                                        DoubleRegister dbl_scratch);
+  int ToInteger32(LConstantOperand* op) const;
+  Operand ToOperand(LOperand* op);
+  MemOperand ToMemOperand(LOperand* op) const;
+  // Returns a MemOperand pointing to the high word of a DoubleStackSlot.
+  MemOperand ToHighMemOperand(LOperand* op) const;
+
   // Try to generate code for the entire chunk, but it may fail if the
   // chunk contains constructs we cannot handle. Returns true if the
   // code generation attempt succeeded.
@@ -136,7 +138,6 @@ class LCodeGen BASE_EMBEDDED {
   LChunk* chunk() const { return chunk_; }
   Scope* scope() const { return scope_; }
   HGraph* graph() const { return chunk_->graph(); }
-  MacroAssembler* masm() const { return masm_; }
 
   Register scratch0() { return r9; }
   DwVfpRegister double_scratch0() { return d0; }
@@ -202,24 +203,6 @@ class LCodeGen BASE_EMBEDDED {
   Register ToRegister(int index) const;
   DoubleRegister ToDoubleRegister(int index) const;
 
-  // LOperand must be a register.
-  Register ToRegister(LOperand* op) const;
-
-  // LOperand is loaded into scratch, unless already a register.
-  Register EmitLoadRegister(LOperand* op, Register scratch);
-
-  // LOperand must be a double register.
-  DoubleRegister ToDoubleRegister(LOperand* op) const;
-
-  // LOperand is loaded into dbl_scratch, unless already a double register.
-  DoubleRegister EmitLoadDoubleRegister(LOperand* op,
-                                        SwVfpRegister flt_scratch,
-                                        DoubleRegister dbl_scratch);
-
-  int ToInteger32(LConstantOperand* op) const;
-  Operand ToOperand(LOperand* op);
-  MemOperand ToMemOperand(LOperand* op) const;
-
   // Specific math operations - used from DoUnaryMathOperation.
   void EmitIntegerMathAbs(LUnaryMathOperation* instr);
   void DoMathAbs(LUnaryMathOperation* instr);

src/arm/lithium-gap-resolver-arm.cc

+// Copyright 2011 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 "arm/lithium-gap-resolver-arm.h"
+#include "arm/lithium-codegen-arm.h"
+
+namespace v8 {
+namespace internal {
+
+static const Register kSavedValueRegister = { 9 };
+static const DoubleRegister kSavedDoubleValueRegister = { 0 };
+
+LGapResolver::LGapResolver(LCodeGen* owner)
+    : cgen_(owner), moves_(32), 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);
+  }
+  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(kSavedDoubleValueRegister, cgen_->ToDoubleRegister(source));
+  } else if (source->IsDoubleStackSlot()) {
+    __ vldr(kSavedDoubleValueRegister, 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_),
+            kSavedDoubleValueRegister);
+  } else if (saved_destination_->IsDoubleStackSlot()) {
+    __ vstr(kSavedDoubleValueRegister,
+            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(kSavedDoubleValueRegister.low(), source_operand);
+          __ vstr(kSavedDoubleValueRegister.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()) {
+    Operand source_operand = cgen_->ToOperand(source);
+    if (destination->IsRegister()) {
+      __ mov(cgen_->ToRegister(destination), source_operand);
+    } else {
+      ASSERT(destination->IsStackSlot());
+      ASSERT(!in_cycle_);  // Constant moves happen after all cycles are gone.
+      MemOperand destination_operand = cgen_->ToMemOperand(destination);
+      __ mov(kSavedValueRegister, source_operand);
+      __ str(kSavedValueRegister, cgen_->ToMemOperand(destination));
+    }
+
+  } else if (source->IsDoubleRegister()) {
+    DoubleRegister source_register = cgen_->ToDoubleRegister(source);
+    if (destination->IsDoubleRegister()) {
+      __ vmov(cgen_->ToDoubleRegister(destination), source_register);
+    } else {
+      ASSERT(destination->IsDoubleStackSlot());
+      MemOperand destination_operand = cgen_->ToMemOperand(destination);
+      __ vstr(source_register, destination_operand);
+    }
+
+  } 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(kSavedDoubleValueRegister, source_operand);
+        __ vstr(kSavedDoubleValueRegister, destination_operand);
+      }
+    }
+  } else {
+    UNREACHABLE();
+  }
+
+  moves_[index].Eliminate();
+}
+
+
+#undef __
+
+} }  // namespace v8::internal

src/arm/lithium-gap-resolver-arm.h

+// Copyright 2011 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.
+
+#ifndef V8_ARM_LITHIUM_GAP_RESOLVER_ARM_H_
+#define V8_ARM_LITHIUM_GAP_RESOLVER_ARM_H_
+
+#include "v8.h"
+
+#include "lithium.h"
+
+namespace v8 {
+namespace internal {
+
+class LCodeGen;
+class LGapResolver;
+
+class LGapResolver BASE_EMBEDDED {
+ public:
+
+  explicit LGapResolver(LCodeGen* owner);
+
+  // Resolve a set of parallel moves, emitting assembler instructions.
+  void Resolve(LParallelMove* parallel_move);
+
+ private:
+  // Build the initial list of moves.
+  void BuildInitialMoveList(LParallelMove* parallel_move);
+
+  // Perform the move at the moves_ index in question (possibly requiring
+  // other moves to satisfy dependencies).
+  void PerformMove(int index);
+
+  // If a cycle is found in the series of moves, save the blocking value to
+  // a scratch register.  The cycle must be found by hitting the root of the
+  // depth-first search.
+  void BreakCycle(int index);
+
+  // After a cycle has been resolved, restore the value from the scratch
+  // register to its proper destination.
+  void RestoreValue();
+
+  // Emit a move and remove it from the move graph.
+  void EmitMove(int index);
+
+  // Verify the move list before performing moves.
+  void Verify();
+
+  LCodeGen* cgen_;
+
+  // List of moves not yet resolved.
+  ZoneList<LMoveOperands> moves_;
+
+  int root_index_;
+  bool in_cycle_;
+  LOperand* saved_destination_;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_ARM_LITHIUM_GAP_RESOLVER_ARM_H_

tools/gyp/v8.gyp

@@ -598,6 +598,8 @@
                 '../../src/arm/lithium-arm.h',
                 '../../src/arm/lithium-codegen-arm.cc',
                 '../../src/arm/lithium-codegen-arm.h',
+                '../../src/arm/lithium-gap-resolver-arm.cc',
+                '../../src/arm/lithium-gap-resolver-arm.h',
                 '../../src/arm/macro-assembler-arm.cc',
                 '../../src/arm/macro-assembler-arm.h',
                 '../../src/arm/regexp-macro-assembler-arm.cc',