[turbofan] simplify gap ordering

test/cctest/compiler/test-jump-threading.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/v8.h"
 #include "test/cctest/cctest.h"
 
 #include "src/compiler/instruction.h"
 #include "src/compiler/instruction-codes.h"
 #include "src/compiler/jump-threading.h"
@@ skipping 42 matching lines @@
     End();
     return pos;
   }
   void Nop() {
     Start();
     sequence_.AddInstruction(Instruction::New(main_zone(), kArchNop));
   }
   void RedundantMoves() {
     Start();
     sequence_.AddInstruction(Instruction::New(main_zone(), kArchNop));
-    int index = static_cast<int>(sequence_.instructions().size()) - 1;
+    int index = static_cast<int>(sequence_.instructions().size()) - 2;
     sequence_.AddGapMove(index, RegisterOperand::Create(13, main_zone()),
                          RegisterOperand::Create(13, main_zone()));
   }
   void NonRedundantMoves() {
     Start();
     sequence_.AddInstruction(Instruction::New(main_zone(), kArchNop));
-    int index = static_cast<int>(sequence_.instructions().size()) - 1;
+    int index = static_cast<int>(sequence_.instructions().size()) - 2;
     sequence_.AddGapMove(index, ImmediateOperand::Create(11, main_zone()),
                          RegisterOperand::Create(11, main_zone()));
   }
   void Other() {
     Start();
     sequence_.AddInstruction(Instruction::New(main_zone(), 155));
   }
   void End() {
     Start();
     sequence_.EndBlock(current_->rpo_number());
@@ skipping 675 matching lines @@
         for (int k = 4; k < 5; k++) assembly[k]--;
       }
       CheckAssemblyOrder(code, 5, assembly);
     }
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8