diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/qemu/int128.h | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/include/qemu/int128.h b/include/qemu/int128.h index bfe7678a04..9ed47aafd3 100644 --- a/include/qemu/int128.h +++ b/include/qemu/int128.h @@ -1,6 +1,10 @@ #ifndef INT128_H #define INT128_H +#include <assert.h> +#include <stdint.h> +#include <stdbool.h> + typedef struct Int128 Int128; struct Int128 { @@ -55,21 +59,26 @@ static inline Int128 int128_rshift(Int128 a, int n) static inline Int128 int128_add(Int128 a, Int128 b) { - Int128 r = { a.lo + b.lo, a.hi + b.hi }; - r.hi += (r.lo < a.lo) || (r.lo < b.lo); - return r; + uint64_t lo = a.lo + b.lo; + + /* a.lo <= a.lo + b.lo < a.lo + k (k is the base, 2^64). Hence, + * a.lo + b.lo >= k implies 0 <= lo = a.lo + b.lo - k < a.lo. + * Similarly, a.lo + b.lo < k implies a.lo <= lo = a.lo + b.lo < k. + * + * So the carry is lo < a.lo. + */ + return (Int128) { lo, (uint64_t)a.hi + b.hi + (lo < a.lo) }; } static inline Int128 int128_neg(Int128 a) { - a.lo = ~a.lo; - a.hi = ~a.hi; - return int128_add(a, int128_one()); + uint64_t lo = -a.lo; + return (Int128) { lo, ~(uint64_t)a.hi + !lo }; } static inline Int128 int128_sub(Int128 a, Int128 b) { - return int128_add(a, int128_neg(b)); + return (Int128){ a.lo - b.lo, a.hi - b.hi - (a.lo < b.lo) }; } static inline bool int128_nonneg(Int128 a) @@ -89,7 +98,7 @@ static inline bool int128_ne(Int128 a, Int128 b) static inline bool int128_ge(Int128 a, Int128 b) { - return int128_nonneg(int128_sub(a, b)); + return a.hi > b.hi || (a.hi == b.hi && a.lo >= b.lo); } static inline bool int128_lt(Int128 a, Int128 b) |