[Turbofan] Reduce register allocation work when we can.

src/compiler/instruction.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/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/instruction.h"
 #include "src/compiler/schedule.h"
 #include "src/compiler/state-values-utils.h"
 
@@ skipping 795 matching lines @@
       zone_(instruction_zone),
       instruction_blocks_(instruction_blocks),
       source_positions_(zone()),
       constants_(ConstantMap::key_compare(),
                  ConstantMap::allocator_type(zone())),
       immediates_(zone()),
       instructions_(zone()),
       next_virtual_register_(0),
       reference_maps_(zone()),
       representations_(zone()),
+      representation_mask_(0),
       deoptimization_entries_(zone()),
       current_block_(nullptr) {}
 
 int InstructionSequence::NextVirtualRegister() {
   int virtual_register = next_virtual_register_++;
   CHECK_NE(virtual_register, InstructionOperand::kInvalidVirtualRegister);
   return virtual_register;
 }
 
 
@@ skipping 85 matching lines @@
                                                int virtual_register) {
   DCHECK_LE(0, virtual_register);
   DCHECK_LT(virtual_register, VirtualRegisterCount());
   if (virtual_register >= static_cast<int>(representations_.size())) {
     representations_.resize(VirtualRegisterCount(), DefaultRepresentation());
   }
   rep = FilterRepresentation(rep);
   DCHECK_IMPLIES(representations_[virtual_register] != rep,
                  representations_[virtual_register] == DefaultRepresentation());
   representations_[virtual_register] = rep;
+  representation_mask_ |= 1 << static_cast<int>(rep);
 }
 
 int InstructionSequence::AddDeoptimizationEntry(
     FrameStateDescriptor* descriptor, DeoptimizeReason reason) {
   int deoptimization_id = static_cast<int>(deoptimization_entries_.size());
   deoptimization_entries_.push_back(DeoptimizationEntry(descriptor, reason));
   return deoptimization_id;
 }
 
 DeoptimizationEntry const& InstructionSequence::GetDeoptimizationEntry(
@@ skipping 135 matching lines @@
   for (int i = 0; i < code.InstructionBlockCount(); i++) {
     printable_block.block_ = code.InstructionBlockAt(RpoNumber::FromInt(i));
     os << printable_block;
   }
   return os;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8