[turbofan] Add backend support for signed loads.

src/compiler/machine-type.h

 // 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.
 
 #ifndef V8_COMPILER_MACHINE_TYPE_H_
 #define V8_COMPILER_MACHINE_TYPE_H_
 
 #include "src/globals.h"
 
 namespace v8 {
@@ skipping 52 matching lines @@
 const MachineType kMachUint32 =
     static_cast<MachineType>(kRepWord32 | kTypeUint32);
 const MachineType kMachInt64 =
     static_cast<MachineType>(kRepWord64 | kTypeInt64);
 const MachineType kMachUint64 =
     static_cast<MachineType>(kRepWord64 | kTypeUint64);
 const MachineType kMachPtr = kPointerSize == 4 ? kRepWord32 : kRepWord64;
 const MachineType kMachAnyTagged =
     static_cast<MachineType>(kRepTagged | kTypeAny);
 
+// Gets only the type of the given type.
+inline MachineType TypeOf(MachineType machine_type) {
+  int result = machine_type & kTypeMask;
+  return static_cast<MachineType>(result);
+}
+
 // Gets only the representation of the given type.
 inline MachineType RepresentationOf(MachineType machine_type) {
   int result = machine_type & kRepMask;
   CHECK(IsPowerOf2(result));
   return static_cast<MachineType>(result);
 }
 
 // Gets the element size in bytes of the machine type.
 inline int ElementSizeOf(MachineType machine_type) {
   switch (RepresentationOf(machine_type)) {
     case kRepBit:
     case kRepWord8:
       return 1;
     case kRepWord16:
       return 2;
     case kRepWord32:
       return 4;
     case kRepWord64:
     case kRepFloat64:
       return 8;
     case kRepTagged:
       return kPointerSize;
     default:
       UNREACHABLE();
       return kPointerSize;
   }
 }
-}
-}
-}  // namespace v8::internal::compiler
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_COMPILER_MACHINE_TYPE_H_