[turbofan] optimize redundant moves around splinter sites

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 {
 
 namespace {
 
 typedef std::pair<InstructionOperand, InstructionOperand> MoveKey;
 
 struct MoveKeyCompare {
   bool operator()(const MoveKey& a, const MoveKey& b) const {
     if (a.first.EqualsCanonicalized(b.first)) {
       return a.second.CompareCanonicalized(b.second);
     }
     return a.first.CompareCanonicalized(b.first);
   }
 };
 
+struct OperandCompare {
+  bool operator()(const InstructionOperand& a,
+                  const InstructionOperand& b) const {
+    return a.CompareCanonicalized(b);
+  }
+};
+
 typedef ZoneMap<MoveKey, unsigned, MoveKeyCompare> MoveMap;
 typedef ZoneSet<InstructionOperand, CompareOperandModuloType> OperandSet;
 
 
-bool GapsCanMoveOver(Instruction* instr) { return instr->IsNop(); }
+bool GapsCanMoveOver(Instruction* instr, Zone* zone) {
+  if (instr->IsNop()) return true;
+  if (instr->ClobbersTemps() || instr->ClobbersRegisters() ||
+      instr->ClobbersDoubleRegisters()) {
+    return false;
+  }
+  if (instr->arch_opcode() != ArchOpcode::kArchNop) return false;
+
+  ZoneSet<InstructionOperand, OperandCompare> operands(zone);
+  for (size_t i = 0; i < instr->InputCount(); ++i) {
+    operands.insert(*instr->InputAt(i));
+  }
+  for (size_t i = 0; i < instr->OutputCount(); ++i) {
+    operands.insert(*instr->OutputAt(i));
+  }
+  for (size_t i = 0; i < instr->TempCount(); ++i) {
+    operands.insert(*instr->TempAt(i));
+  }
+  for (int i = Instruction::GapPosition::FIRST_GAP_POSITION;
+       i <= Instruction::GapPosition::LAST_GAP_POSITION; ++i) {
+    ParallelMove* moves = instr->parallel_moves()[i];
+    if (moves == nullptr) continue;
+    for (MoveOperands* move : *moves) {
+      if (operands.count(move->source()) > 0 ||
+          operands.count(move->destination()) > 0) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
 
 
 int FindFirstNonEmptySlot(Instruction* instr) {
   int i = Instruction::FIRST_GAP_POSITION;
   for (; i <= Instruction::LAST_GAP_POSITION; i++) {
     auto moves = instr->parallel_moves()[i];
     if (moves == nullptr) continue;
     for (auto move : *moves) {
       if (!move->IsRedundant()) return i;
       move->Eliminate();
@@ skipping 89 matching lines @@
         // Smash left into prev_instr, killing left.
         auto pred_moves = prev_instr->parallel_moves()[0];
         CompressMoves(&temp_vector, pred_moves, left);
       }
     }
     if (prev_instr != nullptr) {
       // Slide prev_instr down so we always know where to look for it.
       std::swap(prev_instr->parallel_moves()[0], instr->parallel_moves()[0]);
     }
     prev_instr = instr->parallel_moves()[0] == nullptr ? nullptr : instr;
-    if (GapsCanMoveOver(instr)) continue;
+    if (GapsCanMoveOver(instr, local_zone())) continue;
     if (prev_instr != nullptr) {
       to_finalize_.push_back(prev_instr);
       prev_instr = nullptr;
     }
   }
   if (prev_instr != nullptr) {
     to_finalize_.push_back(prev_instr);
   }
 }
 
@@ skipping 42 matching lines @@
         }
       }
     }
   }
   if (move_map.empty() || correct_counts != move_map.size()) return;
   // Find insertion point.
   Instruction* instr = nullptr;
   for (int i = block->first_instruction_index();
        i <= block->last_instruction_index(); ++i) {
     instr = code()->instructions()[i];
-    if (!GapsCanMoveOver(instr) || !instr->AreMovesRedundant()) break;
+    if (!GapsCanMoveOver(instr, local_zone()) || !instr->AreMovesRedundant())
+      break;
   }
   DCHECK(instr != nullptr);
   bool gap_initialized = true;
   if (instr->parallel_moves()[0] == nullptr ||
       instr->parallel_moves()[0]->empty()) {
     to_finalize_.push_back(instr);
   } else {
     // Will compress after insertion.
     gap_initialized = false;
     std::swap(instr->parallel_moves()[0], instr->parallel_moves()[1]);
@@ skipping 75 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