MIPS: crankshaft implementation

src/mips/lithium-gap-resolver-mips.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 "v8.h"
+
+#include "mips/lithium-gap-resolver-mips.h"
+#include "mips/lithium-codegen-mips.h"
+
+namespace v8 {
+namespace internal {
+
+static const Register kSavedValueRegister = lithiumScratchReg;
+static const DoubleRegister kSavedDoubleValueRegister = lithiumScratchDouble;
+
+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()) {
+    __ lw(kSavedValueRegister, cgen_->ToMemOperand(source));
+  } else if (source->IsDoubleRegister()) {
+    __ mov_d(kSavedDoubleValueRegister, cgen_->ToDoubleRegister(source));
+  } else if (source->IsDoubleStackSlot()) {
+    __ ldc1(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()) {
+    __ sw(kSavedValueRegister, cgen_->ToMemOperand(saved_destination_));
+  } else if (saved_destination_->IsDoubleRegister()) {
+    __ mov_d(cgen_->ToDoubleRegister(saved_destination_),
+            kSavedDoubleValueRegister);
+  } else if (saved_destination_->IsDoubleStackSlot()) {
+    __ sdc1(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());
+      __ sw(source_register, cgen_->ToMemOperand(destination));
+    }
+
+  } else if (source->IsStackSlot()) {
+    MemOperand source_operand = cgen_->ToMemOperand(source);
+    if (destination->IsRegister()) {
+      __ lw(cgen_->ToRegister(destination), source_operand);
+    } else {
+      ASSERT(destination->IsStackSlot());
+      MemOperand destination_operand = cgen_->ToMemOperand(destination);
+      if (in_cycle_) {
+        if (!destination_operand.OffsetIsInt16Encodable()) {
+          // 'at' is overwritten while saving the value to the destination.
+          // Therefore we can't use 'at'.  It is OK if the read from the source
+          // destroys 'at', since that happens before the value is read.
+          // This uses only a single reg of the double reg-pair.
+          __ lwc1(kSavedDoubleValueRegister, source_operand);
+          __ swc1(kSavedDoubleValueRegister, destination_operand);
+        } else {
+          __ lw(at, source_operand);
+          __ sw(at, destination_operand);
+        }
+      } else {
+        __ lw(kSavedValueRegister, source_operand);
+        __ sw(kSavedValueRegister, destination_operand);
+      }
+    }
+
+  } else if (source->IsConstantOperand()) {
+    Operand source_operand = cgen_->ToOperand(source);
+    if (destination->IsRegister()) {
+      __ li(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);
+      __ li(kSavedValueRegister, source_operand);
+      __ sw(kSavedValueRegister, cgen_->ToMemOperand(destination));
+    }
+
+  } else if (source->IsDoubleRegister()) {
+    DoubleRegister source_register = cgen_->ToDoubleRegister(source);
+    if (destination->IsDoubleRegister()) {
+      __ mov_d(cgen_->ToDoubleRegister(destination), source_register);
+    } else {
+      ASSERT(destination->IsDoubleStackSlot());
+      MemOperand destination_operand = cgen_->ToMemOperand(destination);
+      __ sdc1(source_register, destination_operand);
+    }
+
+  } else if (source->IsDoubleStackSlot()) {
+    MemOperand source_operand = cgen_->ToMemOperand(source);
+    if (destination->IsDoubleRegister()) {
+      __ ldc1(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);
+        __ lw(kSavedValueRegister, source_operand);
+        __ sw(kSavedValueRegister, destination_operand);
+        __ lw(kSavedValueRegister, source_high_operand);
+        __ sw(kSavedValueRegister, destination_high_operand);
+      } else {
+        __ ldc1(kSavedDoubleValueRegister, source_operand);
+        __ sdc1(kSavedDoubleValueRegister, destination_operand);
+      }
+    }
+  } else {
+    UNREACHABLE();
+  }
+
+  moves_[index].Eliminate();
+}
+
+
+#undef __
+
+} }  // namespace v8::internal