test_int128.c

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/*-------------------------------------------------------------------------
 *
 * test_int128.c
 *    Testbed for roll-our-own 128-bit integer arithmetic.
 *
 * This is a standalone test program that compares the behavior of an
 * implementation in int128.h to an (assumed correct) int128 native type.
 *
 * Copyright (c) 2017-2025, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/test/modules/test_int128/test_int128.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include <time.h>
 
/* Require a native int128 type */
#ifdef HAVE_INT128
 
/*
 * By default, we test the non-native implementation in int128.h; but
 * by predefining USE_NATIVE_INT128 to 1, you can test the native
 * implementation, just to be sure.
 */
#ifndef USE_NATIVE_INT128
#define USE_NATIVE_INT128 0
#endif
 
#include "common/int128.h"
#include "common/pg_prng.h"
 
/*
 * We assume the parts of this union are laid out compatibly.
 */
typedef union
{
    int128      i128;
    INT128      I128;
    struct
    {
#ifdef WORDS_BIGENDIAN
        int64       hi;
        uint64      lo;
#else
        uint64      lo;
        int64       hi;
#endif
    }           hl;
}           test128;
 
#define INT128_HEX_FORMAT   "%016" PRIx64 "%016" PRIx64
 
/*
 * Control version of comparator.
 */
static inline int
my_int128_compare(int128 x, int128 y)
{
    if (x < y)
        return -1;
    if (x > y)
        return 1;
    return 0;
}
 
/*
 * Main program.
 *
 * Generates a lot of random numbers and tests the implementation for each.
 * The results should be reproducible, since we use a fixed PRNG seed.
 *
 * You can give a loop count if you don't like the default 1B iterations.
 */
int
main(int argc, char **argv)
{
    long        count;
 
    pg_prng_seed(&pg_global_prng_state, (uint64) time(NULL));
 
    if (argc >= 2)
        count = strtol(argv[1], NULL, 0);
    else
        count = 1000000000;
 
    while (count-- > 0)
    {
        int64       x = pg_prng_int64(&pg_global_prng_state);
        int64       y = pg_prng_int64(&pg_global_prng_state);
        int64       z = pg_prng_int64(&pg_global_prng_state);
        int64       w = pg_prng_int64(&pg_global_prng_state);
        int32       z32 = pg_prng_int32(&pg_global_prng_state);
        test128     t1;
        test128     t2;
        test128     t3;
        int32       r1;
        int32       r2;
 
        /* prevent division by zero in the 128/32-bit division test */
        while (z32 == 0)
            z32 = pg_prng_int32(&pg_global_prng_state);
 
        /* check unsigned addition */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 += (int128) (uint64) z;
        int128_add_uint64(&t2.I128, (uint64) z);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " + unsigned %016" PRIx64 "\n", x, y, z);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check signed addition */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 += (int128) z;
        int128_add_int64(&t2.I128, z);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " + signed %016" PRIx64 "\n", x, y, z);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check 128-bit signed addition */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t3.hl.hi = z;
        t3.hl.lo = w;
        t1.i128 += t3.i128;
        int128_add_int128(&t2.I128, t3.I128);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " + " INT128_HEX_FORMAT "\n", x, y, z, w);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check unsigned subtraction */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 -= (int128) (uint64) z;
        int128_sub_uint64(&t2.I128, (uint64) z);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " - unsigned %016" PRIx64 "\n", x, y, z);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check signed subtraction */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 -= (int128) z;
        int128_sub_int64(&t2.I128, z);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " - signed %016" PRIx64 "\n", x, y, z);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check 64x64-bit multiply-add */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 += (int128) z * (int128) w;
        int128_add_int64_mul_int64(&t2.I128, z, w);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " + %016" PRIx64 " * %016" PRIx64 "\n", x, y, z, w);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check 64x64-bit multiply-subtract */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 -= (int128) z * (int128) w;
        int128_sub_int64_mul_int64(&t2.I128, z, w);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " - %016" PRIx64 " * %016" PRIx64 "\n", x, y, z, w);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check 128/32-bit division */
        t3.hl.hi = x;
        t3.hl.lo = y;
        t1.i128 = t3.i128 / z32;
        r1 = (int32) (t3.i128 % z32);
        t2 = t3;
        int128_div_mod_int32(&t2.I128, z32, &r2);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf(INT128_HEX_FORMAT " / signed %08X\n", t3.hl.hi, t3.hl.lo, z32);
            printf("native = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("result = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
        if (r1 != r2)
        {
            printf(INT128_HEX_FORMAT " %% signed %08X\n", t3.hl.hi, t3.hl.lo, z32);
            printf("native = %08X\n", r1);
            printf("result = %08X\n", r2);
            return 1;
        }
 
        /* check comparison */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2.hl.hi = z;
        t2.hl.lo = w;
 
        if (my_int128_compare(t1.i128, t2.i128) !=
            int128_compare(t1.I128, t2.I128))
        {
            printf("comparison failure: %d vs %d\n",
                   my_int128_compare(t1.i128, t2.i128),
                   int128_compare(t1.I128, t2.I128));
            printf("arg1 = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("arg2 = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check case with identical hi parts; above will hardly ever hit it */
        t2.hl.hi = x;
 
        if (my_int128_compare(t1.i128, t2.i128) !=
            int128_compare(t1.I128, t2.I128))
        {
            printf("comparison failure: %d vs %d\n",
                   my_int128_compare(t1.i128, t2.i128),
                   int128_compare(t1.I128, t2.I128));
            printf("arg1 = " INT128_HEX_FORMAT "\n", t1.hl.hi, t1.hl.lo);
            printf("arg2 = " INT128_HEX_FORMAT "\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
    }
 
    return 0;
}
 
#else                           /* ! HAVE_INT128 */
 
/*
 * For now, do nothing if we don't have a native int128 type.
 */
int
main(int argc, char **argv)
{
    printf("skipping tests: no native int128 type\n");
    return 0;
}
 
#endif