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

src/runtime/runtime.h

Index: src/runtime/runtime.h
diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h
index d6a98c96a7752f3731eeee4737a084f1d55e0a6e..7db60a142f908ccd4b5a34b2a53c79b216a671f7 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -1234,26 +1234,10 @@ 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