Change the algorithm and generated code for parallel moves on IA32.

src/ia32/lithium-gap-resolver-ia32.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_IA32_LITHIUM_GAP_RESOLVER_IA32_H_
+#define V8_IA32_LITHIUM_GAP_RESOLVER_IA32_H_
+
+#include "v8.h"
+
+#include "lithium-allocator.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);
+
+  // Emit any code necessary at the end of a gap move.
+  void Finish();
+
+  // Add or delete a move from the move graph without emitting any code.
+  // Used to build up the graph and remove trivial moves.
+  void AddMove(LMoveOperands move);
+  void RemoveMove(int index);
+
+  // Report the count of uses of operand as a source in a not-yet-performed
+  // move.  Used to rebuild use counts.
+  int CountSourceUses(LOperand* operand);
+
+  // Emit a move and remove it from the move graph.
+  void EmitMove(int index);
+
+  // Execute a move by emitting a swap of two operands.  The move from
+  // source to destination is removed from the move graph.
+  void EmitSwap(int index);
+
+  // Ensure that the given operand is not spilled.
+  void EnsureRestored(LOperand* operand);
+
+  // Return a register that can be used as a temp register, spilling
+  // something if necessary.
+  Register EnsureTempRegister();
+
+  // Return a known free register different from the given one (which could
+  // be no_reg---returning any free register), or no_reg if there is no such
+  // register.
+  Register GetFreeRegisterNot(Register reg);
+
+  // Verify that the state is the initial one, ready to resolve a single
+  // parallel move.
+  bool HasBeenReset();
+
+  LCodeGen* cgen_;
+
+  // List of moves not yet resolved.
+  ZoneList<LMoveOperands> moves_;
+
+  // Source and destination use counts for all the registers.
+  int general_source_uses_[Register::kNumAllocatableRegisters];
+  int general_destination_uses_[Register::kNumAllocatableRegisters];
+  int double_source_uses_[DoubleRegister::kNumAllocatableRegisters];
+  int double_destination_uses_[DoubleRegister::kNumAllocatableRegisters];
+
+  // If we had to spill on demand, the currently spilled register's
+  // allocation index.
+  int spilled_register_;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_IA32_LITHIUM_GAP_RESOLVER_IA32_H_