CSE2410 Fall 2014 Bounce

// Copyright 2011 the V8 project authors. All rights reserved.

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#include "v8.h"

#if V8_TARGET_ARCH_X64

#include "x64/lithium-gap-resolver-x64.h"

#include "x64/lithium-codegen-x64.h"

namespace v8 {

namespace internal {

LGapResolver::LGapResolver(LCodeGen* owner)

    : cgen_(owner), moves_(32, owner->zone()) {}

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()) {

      PerformMove(i);

    }

  }

  // 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 use operand swaps to resolve cycles,

  // which means that a call to PerformMove could change any source operand

  // in the move graph.

  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.  Recursion may allow

  // multiple moves to be pending.

  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()) {

      // Though PerformMove can change any source operand in the move graph,

      // this call cannot create a blocking move via a swap (this loop does

      // not miss any).  Assume there is a non-blocking move with source A

      // and this move is blocked on source B and there is a swap of A and

      // B.  Then A and B must be involved in the same cycle (or they would

      // not be swapped).  Since this move's destination is B and there is

      // only a single incoming edge to an operand, this move must also be

      // involved in the same cycle.  In that case, the blocking move will

      // be created but will be "pending" when we return from PerformMove.

      PerformMove(i);

    }

  }

  // We are about to resolve this move and don't need it marked as

  // pending, so restore its destination.

  moves_[index].set_destination(destination);

  // This move's source may have changed due to swaps to resolve cycles and

  // so it may now be the last move in the cycle.  If so remove it.

  if (moves_[index].source()->Equals(destination)) {

    moves_[index].Eliminate();

    return;

  }

  // The move may be blocked on a (at most one) pending move, in which case

  // we have a cycle.  Search for such a blocking move and perform a swap to

  // resolve it.

  for (int i = 0; i < moves_.length(); ++i) {

    LMoveOperands other_move = moves_[i];

    if (other_move.Blocks(destination)) {

      ASSERT(other_move.IsPending());

      EmitSwap(index);

      return;

    }

  }

  // This move is not 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::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 src = cgen_->ToRegister(source);

    if (destination->IsRegister()) {

      Register dst = cgen_->ToRegister(destination);

      __ movq(dst, src);

    } else {

      ASSERT(destination->IsStackSlot());

      Operand dst = cgen_->ToOperand(destination);

      __ movq(dst, src);

    }

  } else if (source->IsStackSlot()) {

    Operand src = cgen_->ToOperand(source);

    if (destination->IsRegister()) {

      Register dst = cgen_->ToRegister(destination);

      __ movq(dst, src);

    } else {

      ASSERT(destination->IsStackSlot());

      Operand dst = cgen_->ToOperand(destination);

      __ movq(kScratchRegister, src);

      __ movq(dst, kScratchRegister);

    }

  } else if (source->IsConstantOperand()) {

    LConstantOperand* constant_source = LConstantOperand::cast(source);

    if (destination->IsRegister()) {

      Register dst = cgen_->ToRegister(destination);

      if (cgen_->IsSmiConstant(constant_source)) {

        __ Move(dst, cgen_->ToSmi(constant_source));

      } else if (cgen_->IsInteger32Constant(constant_source)) {

        __ movl(dst, Immediate(cgen_->ToInteger32(constant_source)));

      } else {

        __ Move(dst, cgen_->ToHandle(constant_source));

      }

    } else if (destination->IsDoubleRegister()) {

      double v = cgen_->ToDouble(constant_source);

      uint64_t int_val = BitCast<uint64_t, double>(v);

      XMMRegister dst = cgen_->ToDoubleRegister(destination);

      if (int_val == 0) {

        __ xorps(dst, dst);

      } else {

        __ movq(kScratchRegister, int_val, RelocInfo::NONE64);

        __ movq(dst, kScratchRegister);

      }

    } else {

      ASSERT(destination->IsStackSlot());

      Operand dst = cgen_->ToOperand(destination);

      if (cgen_->IsSmiConstant(constant_source)) {

        __ Move(dst, cgen_->ToSmi(constant_source));

      } else if (cgen_->IsInteger32Constant(constant_source)) {

        // Zero top 32 bits of a 64 bit spill slot that holds a 32 bit untagged

        // value.

        __ movq(dst, Immediate(cgen_->ToInteger32(constant_source)));

      } else {

        __ Move(kScratchRegister, cgen_->ToHandle(constant_source));

        __ movq(dst, kScratchRegister);

      }

    }

  } else if (source->IsDoubleRegister()) {

    XMMRegister src = cgen_->ToDoubleRegister(source);

    if (destination->IsDoubleRegister()) {

      __ movaps(cgen_->ToDoubleRegister(destination), src);

    } else {

      ASSERT(destination->IsDoubleStackSlot());

      __ movsd(cgen_->ToOperand(destination), src);

    }

  } else if (source->IsDoubleStackSlot()) {

    Operand src = cgen_->ToOperand(source);

    if (destination->IsDoubleRegister()) {

      __ movsd(cgen_->ToDoubleRegister(destination), src);

    } else {

      ASSERT(destination->IsDoubleStackSlot());

      __ movsd(xmm0, src);

      __ movsd(cgen_->ToOperand(destination), xmm0);

    }

  } else {

    UNREACHABLE();

  }

  moves_[index].Eliminate();

}

void LGapResolver::EmitSwap(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() && destination->IsRegister()) {

    // Swap two general-purpose registers.

    Register src = cgen_->ToRegister(source);

    Register dst = cgen_->ToRegister(destination);

    __ xchgq(dst, src);

  } else if ((source->IsRegister() && destination->IsStackSlot()) ||

             (source->IsStackSlot() && destination->IsRegister())) {

    // Swap a general-purpose register and a stack slot.

    Register reg =

        cgen_->ToRegister(source->IsRegister() ? source : destination);

    Operand mem =

        cgen_->ToOperand(source->IsRegister() ? destination : source);

    __ movq(kScratchRegister, mem);

    __ movq(mem, reg);

    __ movq(reg, kScratchRegister);

  } else if ((source->IsStackSlot() && destination->IsStackSlot()) ||

      (source->IsDoubleStackSlot() && destination->IsDoubleStackSlot())) {

    // Swap two stack slots or two double stack slots.

    Operand src = cgen_->ToOperand(source);

    Operand dst = cgen_->ToOperand(destination);

    __ movsd(xmm0, src);

    __ movq(kScratchRegister, dst);

    __ movsd(dst, xmm0);

    __ movq(src, kScratchRegister);

  } else if (source->IsDoubleRegister() && destination->IsDoubleRegister()) {

    // Swap two double registers.

    XMMRegister source_reg = cgen_->ToDoubleRegister(source);

    XMMRegister destination_reg = cgen_->ToDoubleRegister(destination);

    __ movaps(xmm0, source_reg);

    __ movaps(source_reg, destination_reg);

    __ movaps(destination_reg, xmm0);

  } else if (source->IsDoubleRegister() || destination->IsDoubleRegister()) {

    // Swap a double register and a double stack slot.

    ASSERT((source->IsDoubleRegister() && destination->IsDoubleStackSlot()) ||

           (source->IsDoubleStackSlot() && destination->IsDoubleRegister()));

    XMMRegister reg = cgen_->ToDoubleRegister(source->IsDoubleRegister()

                                                  ? source

                                                  : destination);

    LOperand* other = source->IsDoubleRegister() ? destination : source;

    ASSERT(other->IsDoubleStackSlot());

    Operand other_operand = cgen_->ToOperand(other);

    __ movsd(xmm0, other_operand);

    __ movsd(other_operand, reg);

    __ movsd(reg, xmm0);

  } else {

    // No other combinations are possible.

    UNREACHABLE();

  }

  // The swap of source and destination has executed a move from source to

  // destination.

  moves_[index].Eliminate();

  // Any unperformed (including pending) move with a source of either

  // this move's source or destination needs to have their source

  // changed to reflect the state of affairs after the swap.

  for (int i = 0; i < moves_.length(); ++i) {

    LMoveOperands other_move = moves_[i];

    if (other_move.Blocks(source)) {

      moves_[i].set_source(destination);

    } else if (other_move.Blocks(destination)) {

      moves_[i].set_source(source);

    }

  }

}

#undef __

} }  // namespace v8::internal

#endif  // V8_TARGET_ARCH_X64