int128: Use __int128 if available

Reviewed-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

include/qemu/int128.h

@@ -1,6 +1,138 @@
 #ifndef INT128_H
 #define INT128_H
 
+#ifdef CONFIG_INT128
+
+typedef __int128_t Int128;
+
+static inline Int128 int128_make64(uint64_t a)
+{
+    return a;
+}
+
+static inline uint64_t int128_get64(Int128 a)
+{
+    uint64_t r = a;
+    assert(r == a);
+    return r;
+}
+
+static inline uint64_t int128_getlo(Int128 a)
+{
+    return a;
+}
+
+static inline int64_t int128_gethi(Int128 a)
+{
+    return a >> 64;
+}
+
+static inline Int128 int128_zero(void)
+{
+    return 0;
+}
+
+static inline Int128 int128_one(void)
+{
+    return 1;
+}
+
+static inline Int128 int128_2_64(void)
+{
+    return (Int128)1 << 64;
+}
+
+static inline Int128 int128_exts64(int64_t a)
+{
+    return a;
+}
+
+static inline Int128 int128_and(Int128 a, Int128 b)
+{
+    return a & b;
+}
+
+static inline Int128 int128_rshift(Int128 a, int n)
+{
+    return a >> n;
+}
+
+static inline Int128 int128_add(Int128 a, Int128 b)
+{
+    return a + b;
+}
+
+static inline Int128 int128_neg(Int128 a)
+{
+    return -a;
+}
+
+static inline Int128 int128_sub(Int128 a, Int128 b)
+{
+    return a - b;
+}
+
+static inline bool int128_nonneg(Int128 a)
+{
+    return a >= 0;
+}
+
+static inline bool int128_eq(Int128 a, Int128 b)
+{
+    return a == b;
+}
+
+static inline bool int128_ne(Int128 a, Int128 b)
+{
+    return a != b;
+}
+
+static inline bool int128_ge(Int128 a, Int128 b)
+{
+    return a >= b;
+}
+
+static inline bool int128_lt(Int128 a, Int128 b)
+{
+    return a < b;
+}
+
+static inline bool int128_le(Int128 a, Int128 b)
+{
+    return a <= b;
+}
+
+static inline bool int128_gt(Int128 a, Int128 b)
+{
+    return a > b;
+}
+
+static inline bool int128_nz(Int128 a)
+{
+    return a != 0;
+}
+
+static inline Int128 int128_min(Int128 a, Int128 b)
+{
+    return a < b ? a : b;
+}
+
+static inline Int128 int128_max(Int128 a, Int128 b)
+{
+    return a > b ? a : b;
+}
+
+static inline void int128_addto(Int128 *a, Int128 b)
+{
+    *a += b;
+}
+
+static inline void int128_subfrom(Int128 *a, Int128 b)
+{
+    *a -= b;
+}
+
+#else /* !CONFIG_INT128 */
 
 typedef struct Int128 Int128;
 
@@ -153,4 +285,5 @@ static inline void int128_subfrom(Int128 *a, Int128 b)
     *a = int128_sub(*a, b);
 }
 
-#endif
+#endif /* CONFIG_INT128 */
+#endif /* INT128_H */