[Atomics] Remove support for atomic accesses on floating-point values.

src/runtime/runtime.h

 // Copyright 2012 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_RUNTIME_RUNTIME_H_
 #define V8_RUNTIME_RUNTIME_H_
 
 #include "src/allocation.h"
 #include "src/objects.h"
 #include "src/unicode.h"
@@ skipping 1216 matching lines @@
 class AllocateTargetSpace : public BitField<AllocationSpace, 1, 3> {};
 
 class DeclareGlobalsEvalFlag : public BitField<bool, 0, 1> {};
 class DeclareGlobalsNativeFlag : public BitField<bool, 1, 1> {};
 STATIC_ASSERT(LANGUAGE_END == 3);
 class DeclareGlobalsLanguageMode : public BitField<LanguageMode, 2, 2> {};
 
 //---------------------------------------------------------------------------
 // Inline functions
 
-// Assume that 32-bit architectures don't have 64-bit atomic ops.
-// TODO(binji): can we do better here?
-#if V8_TARGET_ARCH_64_BIT && V8_HOST_ARCH_64_BIT
-
-#define ATOMICS_REQUIRE_LOCK_64_BIT 0
-
-inline bool Runtime::AtomicIsLockFree(uint32_t size) {
-  return size == 1 || size == 2 || size == 4 || size == 8;
-}
-
-#else
-
-#define ATOMICS_REQUIRE_LOCK_64_BIT 1
-
 inline bool Runtime::AtomicIsLockFree(uint32_t size) {
   return size == 1 || size == 2 || size == 4;
 }
 
-#endif
-
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_RUNTIME_RUNTIME_H_