[turbofan] Remove Instruction::IsControl() and Instruction::MarkAsControl()

src/compiler/register-allocator.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/linkage.h"
 #include "src/compiler/register-allocator.h"
 #include "src/string-stream.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 2426 matching lines @@
 }
 
 
 LiveRange* RegisterAllocator::SplitRangeAt(LiveRange* range,
                                            LifetimePosition pos) {
   DCHECK(!range->IsFixed());
   TraceAlloc("Splitting live range %d at %d\n", range->id(), pos.Value());
 
   if (pos.Value() <= range->Start().Value()) return range;
 
-  // We can't properly connect liveranges if split occured at the end
-  // of control instruction.
+  // We can't properly connect liveranges if splitting occurred at the end
+  // a block.
   DCHECK(pos.IsInstructionStart() ||
-         !InstructionAt(pos.InstructionIndex())->IsControl());
+         (code()->GetInstructionBlock(pos.InstructionIndex()))
+                 ->last_instruction_index() != pos.InstructionIndex());
 
   int vreg = GetVirtualRegister();
   auto result = LiveRangeFor(vreg);
   range->SplitAt(pos, result, local_zone());
   return result;
 }
 
 
 LiveRange* RegisterAllocator::SplitBetween(LiveRange* range,
                                            LifetimePosition start,
@@ skipping 121 matching lines @@
   } else {
     DCHECK(range->Kind() == GENERAL_REGISTERS);
     assigned_registers_->Add(reg);
   }
   range->set_assigned_register(reg, operand_cache());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8