[turbofan] Build s/NULL/nullptr/g and CHECK(x != nullptr) to CHECK_NOT_NULL(x).

src/compiler/x87/code-generator-x87.cc

Index: src/compiler/x87/code-generator-x87.cc
diff --git a/src/compiler/x87/code-generator-x87.cc b/src/compiler/x87/code-generator-x87.cc
index 5bff2c5d59dadd5638b31b84d31ccf874891ab50..e8e094577d3bde8be4f9ee617ac778bac6eab5fc 100644
--- a/src/compiler/x87/code-generator-x87.cc
+++ b/src/compiler/x87/code-generator-x87.cc
@@ -662,7 +662,7 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       InstructionOperand* source = instr->InputAt(0);
       InstructionOperand* destination = instr->Output();
       DCHECK(source->IsConstant());
-      X87OperandConverter g(this, NULL);
+      X87OperandConverter g(this, nullptr);
       Constant src_constant = g.ToConstant(source);
 
       DCHECK_EQ(Constant::kFloat64, src_constant.type());
@@ -1765,7 +1765,7 @@ void CodeGenerator::AssembleReturn() {
 
 void CodeGenerator::AssembleMove(InstructionOperand* source,
                                  InstructionOperand* destination) {
-  X87OperandConverter g(this, NULL);
+  X87OperandConverter g(this, nullptr);
   // Dispatch on the source and destination operand kinds.  Not all
   // combinations are possible.
   if (source->IsRegister()) {
@@ -1909,7 +1909,7 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
 
 void CodeGenerator::AssembleSwap(InstructionOperand* source,
                                  InstructionOperand* destination) {
-  X87OperandConverter g(this, NULL);
+  X87OperandConverter g(this, nullptr);
   // Dispatch on the source and destination operand kinds.  Not all
   // combinations are possible.
   if (source->IsRegister() && destination->IsRegister()) {