[Turbofan] Add the concept of aliasing to RegisterConfiguration.

src/compiler/move-optimizer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/move-optimizer.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
@@ skipping 10 matching lines @@
       return a.destination.CompareCanonicalized(b.destination);
     }
     return a.source.CompareCanonicalized(b.source);
   }
 };
 
 typedef ZoneMap<MoveKey, unsigned, MoveKeyCompare> MoveMap;
 typedef ZoneSet<InstructionOperand, CompareOperandModuloType> OperandSet;
 
 bool Blocks(const OperandSet& set, const InstructionOperand& operand) {
-  if (!operand.IsFPRegister()) return set.find(operand) != set.end();
+  if (set.find(operand) != set.end()) return true;
+  // Only FP registers alias.
+  if (!operand.IsFPRegister()) return false;
 
   const LocationOperand& loc = LocationOperand::cast(operand);
-  if (loc.representation() == MachineRepresentation::kFloat64) {
-    return set.find(operand) != set.end() ||
-           set.find(LocationOperand(loc.kind(), loc.location_kind(),
-                                    MachineRepresentation::kFloat32,
-                                    loc.register_code())) != set.end();
+  MachineRepresentation rep = loc.representation();
+  MachineRepresentation other_fp_rep = rep == MachineRepresentation::kFloat64
+                                           ? MachineRepresentation::kFloat32
+                                           : MachineRepresentation::kFloat64;
+  const RegisterConfiguration* config =
+      RegisterConfiguration::ArchDefault(RegisterConfiguration::TURBOFAN);
+  if (config->fp_aliasing_kind() != RegisterConfiguration::COMBINE) {
+    // Overlap aliasing case.
+    return set.find(LocationOperand(loc.kind(), loc.location_kind(),
+                                    other_fp_rep, loc.register_code())) !=
+           set.end();
   }
-  DCHECK_EQ(MachineRepresentation::kFloat32, loc.representation());
-  return set.find(operand) != set.end() ||
-         set.find(LocationOperand(loc.kind(), loc.location_kind(),
-                                  MachineRepresentation::kFloat64,
-                                  loc.register_code())) != set.end();
+  // Combine aliasing case.
+  int alias_base_index = -1;
+  int aliases = config->GetAliases(rep, loc.register_code(), other_fp_rep,
+                                   &alias_base_index);
+  while (aliases--) {
+    int aliased_reg = alias_base_index + aliases;
+    if (set.find(LocationOperand(loc.kind(), loc.location_kind(), other_fp_rep,
+                                 aliased_reg)) != set.end())
+      return true;
+  }
+  return false;
 }
 
 int FindFirstNonEmptySlot(const Instruction* instr) {
   int i = Instruction::FIRST_GAP_POSITION;
   for (; i <= Instruction::LAST_GAP_POSITION; i++) {
     ParallelMove* moves = instr->parallel_moves()[i];
     if (moves == nullptr) continue;
     for (MoveOperands* move : *moves) {
       if (!move->IsRedundant()) return i;
       move->Eliminate();
@@ skipping 432 matching lines @@
         static_cast<Instruction::GapPosition>(1), code_zone());
     slot_1->AddMove(group_begin->destination(), load->destination());
     load->Eliminate();
   }
   loads.clear();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8