[turbofan] Make MachineType a pair of enums.

src/compiler/simplified-operator.cc

Index: src/compiler/simplified-operator.cc
diff --git a/src/compiler/simplified-operator.cc b/src/compiler/simplified-operator.cc
index 5b973e1a94f9c4af5038485dd74e5ed4177667dd..1eaa287fee5d7ac807b5c978b00f96afe9e08f7c 100644
--- a/src/compiler/simplified-operator.cc
+++ b/src/compiler/simplified-operator.cc
@@ -29,24 +29,24 @@ MachineType BufferAccess::machine_type() const {
   switch (external_array_type_) {
     case kExternalUint8Array:
     case kExternalUint8ClampedArray:
-      return kMachUint8;
+      return MachineType::Uint8();
     case kExternalInt8Array:
-      return kMachInt8;
+      return MachineType::Int8();
     case kExternalUint16Array:
-      return kMachUint16;
+      return MachineType::Uint16();
     case kExternalInt16Array:
-      return kMachInt16;
+      return MachineType::Int16();
     case kExternalUint32Array:
-      return kMachUint32;
+      return MachineType::Uint32();
     case kExternalInt32Array:
-      return kMachInt32;
+      return MachineType::Int32();
     case kExternalFloat32Array:
-      return kMachFloat32;
+      return MachineType::Float32();
     case kExternalFloat64Array:
-      return kMachFloat64;
+      return MachineType::Float64();
   }
   UNREACHABLE();
-  return kMachNone;
+  return MachineType::None();
 }