6046c62086
For add, the carry only requires checking one of the arguments. For sub and neg, we can similarly optimize computation of the carry. For ge, we can just do lexicographic order. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
145 lines
2.6 KiB
C
145 lines
2.6 KiB
C
#ifndef INT128_H
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#define INT128_H
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#include <assert.h>
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#include <stdint.h>
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#include <stdbool.h>
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typedef struct Int128 Int128;
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struct Int128 {
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uint64_t lo;
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int64_t hi;
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};
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static inline Int128 int128_make64(uint64_t a)
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{
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return (Int128) { a, 0 };
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}
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static inline uint64_t int128_get64(Int128 a)
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{
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assert(!a.hi);
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return a.lo;
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}
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static inline Int128 int128_zero(void)
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{
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return int128_make64(0);
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}
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static inline Int128 int128_one(void)
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{
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return int128_make64(1);
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}
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static inline Int128 int128_2_64(void)
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{
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return (Int128) { 0, 1 };
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}
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static inline Int128 int128_and(Int128 a, Int128 b)
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{
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return (Int128) { a.lo & b.lo, a.hi & b.hi };
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}
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static inline Int128 int128_rshift(Int128 a, int n)
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{
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int64_t h;
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if (!n) {
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return a;
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}
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h = a.hi >> (n & 63);
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if (n >= 64) {
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return (Int128) { h, h >> 63 };
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} else {
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return (Int128) { (a.lo >> n) | (a.hi << (64 - n)), h };
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}
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}
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static inline Int128 int128_add(Int128 a, Int128 b)
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{
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uint64_t lo = a.lo + b.lo;
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/* a.lo <= a.lo + b.lo < a.lo + k (k is the base, 2^64). Hence,
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* a.lo + b.lo >= k implies 0 <= lo = a.lo + b.lo - k < a.lo.
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* Similarly, a.lo + b.lo < k implies a.lo <= lo = a.lo + b.lo < k.
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*
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* So the carry is lo < a.lo.
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*/
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return (Int128) { lo, (uint64_t)a.hi + b.hi + (lo < a.lo) };
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}
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static inline Int128 int128_neg(Int128 a)
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{
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uint64_t lo = -a.lo;
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return (Int128) { lo, ~(uint64_t)a.hi + !lo };
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}
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static inline Int128 int128_sub(Int128 a, Int128 b)
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{
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return (Int128){ a.lo - b.lo, a.hi - b.hi - (a.lo < b.lo) };
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}
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static inline bool int128_nonneg(Int128 a)
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{
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return a.hi >= 0;
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}
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static inline bool int128_eq(Int128 a, Int128 b)
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{
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return a.lo == b.lo && a.hi == b.hi;
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}
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static inline bool int128_ne(Int128 a, Int128 b)
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{
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return !int128_eq(a, b);
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}
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static inline bool int128_ge(Int128 a, Int128 b)
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{
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return a.hi > b.hi || (a.hi == b.hi && a.lo >= b.lo);
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}
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static inline bool int128_lt(Int128 a, Int128 b)
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{
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return !int128_ge(a, b);
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}
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static inline bool int128_le(Int128 a, Int128 b)
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{
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return int128_ge(b, a);
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}
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static inline bool int128_gt(Int128 a, Int128 b)
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{
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return !int128_le(a, b);
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}
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static inline bool int128_nz(Int128 a)
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{
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return a.lo || a.hi;
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}
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static inline Int128 int128_min(Int128 a, Int128 b)
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{
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return int128_le(a, b) ? a : b;
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}
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static inline Int128 int128_max(Int128 a, Int128 b)
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{
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return int128_ge(a, b) ? a : b;
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}
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static inline void int128_addto(Int128 *a, Int128 b)
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{
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*a = int128_add(*a, b);
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}
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static inline void int128_subfrom(Int128 *a, Int128 b)
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{
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*a = int128_sub(*a, b);
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}
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#endif
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