+/**
+ * Add two signed 64-bit values with saturation.
+ *
+ * @param a one value
+ * @param b another value
+ * @return sum with signed saturation
+ */
+static av_always_inline int64_t av_sat_add64_c(int64_t a, int64_t b) {
+#if (!defined(__INTEL_COMPILER) && AV_GCC_VERSION_AT_LEAST(5,1)) || AV_HAS_BUILTIN(__builtin_add_overflow)
+ int64_t tmp;
+ return !__builtin_add_overflow(a, b, &tmp) ? tmp : (tmp < 0 ? INT64_MAX : INT64_MIN);
+#else
+ if (b >= 0 && a >= INT64_MAX - b)
+ return INT64_MAX;
+ if (b <= 0 && a <= INT64_MIN - b)
+ return INT64_MIN;
+ return a + b;
+#endif
+}
+
+/**
+ * Subtract two signed 64-bit values with saturation.
+ *
+ * @param a one value
+ * @param b another value
+ * @return difference with signed saturation
+ */
+static av_always_inline int64_t av_sat_sub64_c(int64_t a, int64_t b) {
+#if (!defined(__INTEL_COMPILER) && AV_GCC_VERSION_AT_LEAST(5,1)) || AV_HAS_BUILTIN(__builtin_sub_overflow)
+ int64_t tmp;
+ return !__builtin_sub_overflow(a, b, &tmp) ? tmp : (tmp < 0 ? INT64_MAX : INT64_MIN);
+#else
+ if (b <= 0 && a >= INT64_MAX + b)
+ return INT64_MAX;
+ if (b >= 0 && a <= INT64_MIN + b)
+ return INT64_MIN;
+ return a - b;
+#endif
+}
+