Use C++20 [[unlikely]] and defaulted operator== (#5630)

Summary:
X-link: https://github.com/facebookresearch/FBGEMM/pull/2581

Pull Request resolved: #5630

Reviewed By: cthi

Differential Revision: D100759719

Pulled By: q10

fbshipit-source-id: 4f81a8193c6f90ddc4370de2a51e9b0465e5f4d1

Author: cyyever

include/fbgemm/Assert.h

@@ -67,14 +67,8 @@ auto fbgemmCheckMsg(const char* defaultMsg, const Args&... args) {
 // unceremoniously quit the process (unlike assert()).
 ////////////////////////////////////////////////////////////////////////////////
 
-#if defined(__GNUC__) || defined(__ICL) || defined(__clang__)
-#define FBGEMM_UNLIKELY(expr) (__builtin_expect(static_cast<bool>(expr), 0))
-#else
-#define FBGEMM_UNLIKELY(expr) (expr)
-#endif
-
 #define FBGEMM_CHECK(cond, ...)                                 \
-  if (FBGEMM_UNLIKELY(!(cond))) {                               \
+  if (!(cond)) [[unlikely]] {                                   \
     throw ::fbgemm::Error(                                      \
         ::fbgemm::detail::fbgemmCheckMsg(                       \
             "Expected " #cond " to be true, but got false.  "   \

src/EmbeddingStatsTracker.h

@@ -128,15 +128,7 @@ class EmbeddingStatsTracker {
           input_data_type(input_dt),
           output_data_type(output_dt) {}
 
-    // Equality operator for hash map
-    // Used by the unordered_map to determine if two AccessPatternEntry objects
-    // represent the same entry
-    bool operator==(const AccessPatternEntry& other) const {
-      return rows == other.rows && dims == other.dims &&
-          batch_size == other.batch_size && bag_size == other.bag_size &&
-          input_data_type == other.input_data_type &&
-          output_data_type == other.output_data_type;
-    }
+    bool operator==(const AccessPatternEntry&) const = default;
 
     // Generate a string representation for debugging and logging purposes
     std::string toString() const {