tests/fp/fp-test-log2.c

   1 /*
   2  * fp-test-log2.c - test QEMU's softfloat log2
   3  *
   4  * Copyright (C) 2020, Linaro, Ltd.
   5  *
   6  * License: GNU GPL, version 2 or later.
   7  *   See the COPYING file in the top-level directory.
   8  */
   9 #ifndef HW_POISON_H
  10 #error Must define HW_POISON_H to work around TARGET_* poisoning
  11 #endif
  12
  13 #include "qemu/osdep.h"
  14 #include "qemu/cutils.h"
  15 #include <math.h>
  16 #include "fpu/softfloat.h"
  17
  18 typedef union {
  19     double d;
  20     float64 i;
  21 } ufloat64;
  22
  23 static int errors;
  24
  25 static void compare(ufloat64 test, ufloat64 real, ufloat64 soft, bool exact)
  26 {
  27     int msb;
  28     uint64_t ulp = UINT64_MAX;
  29
  30     if (real.i == soft.i) {
  31         return;
  32     }
  33     msb = 63 - __builtin_clzll(real.i ^ soft.i);
  34
  35     if (msb < 52) {
  36         if (real.i > soft.i) {
  37             ulp = real.i - soft.i;
  38         } else {
  39             ulp = soft.i - real.i;
  40         }
  41     }
  42
  43     /* glibc allows 3 ulp error in its libm-test-ulps; allow 4 here */
  44     if (!exact && ulp <= 4) {
  45         return;
  46     }
  47
  48     printf("test: %016" PRIx64 "  %+.13a\n"
  49            "  sf: %016" PRIx64 "  %+.13a\n"
  50            "libm: %016" PRIx64 "  %+.13a\n",
  51            test.i, test.d, soft.i, soft.d, real.i, real.d);
  52
  53     if (msb == 63) {
  54         printf("Error in sign!\n\n");
  55     } else if (msb >= 52) {
  56         printf("Error in exponent: %d\n\n",
  57                (int)(soft.i >> 52) - (int)(real.i >> 52));
  58     } else {
  59         printf("Error in fraction: %" PRIu64 " ulp\n\n", ulp);
  60     }
  61
  62     if (++errors == 20) {
  63         exit(1);
  64     }
  65 }
  66
  67 int main(int ac, char **av)
  68 {
  69     ufloat64 test, real, soft;
  70     float_status qsf = {0};
  71     int i;
  72
  73     set_float_rounding_mode(float_round_nearest_even, &qsf);
  74
  75     test.d = 0.0;
  76     real.d = -__builtin_inf();
  77     soft.i = float64_log2(test.i, &qsf);
  78     compare(test, real, soft, true);
  79
  80     test.d = 1.0;
  81     real.d = 0.0;
  82     soft.i = float64_log2(test.i, &qsf);
  83     compare(test, real, soft, true);
  84
  85     test.d = 2.0;
  86     real.d = 1.0;
  87     soft.i = float64_log2(test.i, &qsf);
  88     compare(test, real, soft, true);
  89
  90     test.d = 4.0;
  91     real.d = 2.0;
  92     soft.i = float64_log2(test.i, &qsf);
  93     compare(test, real, soft, true);
  94
  95     test.d = 0x1p64;
  96     real.d = 64.0;
  97     soft.i = float64_log2(test.i, &qsf);
  98     compare(test, real, soft, true);
  99
 100     test.d = __builtin_inf();
 101     real.d = __builtin_inf();
 102     soft.i = float64_log2(test.i, &qsf);
 103     compare(test, real, soft, true);
 104
 105     for (i = 0; i < 10000; ++i) {
 106         test.d = drand48() + 1.0;    /* [1.0, 2.0) */
 107         real.d = log2(test.d);
 108         soft.i = float64_log2(test.i, &qsf);
 109         compare(test, real, soft, false);
 110
 111         test.d = drand48() * 100;    /* [0.0, 100) */
 112         real.d = log2(test.d);
 113         soft.i = float64_log2(test.i, &qsf);
 114         compare(test, real, soft, false);
 115     }
 116
 117     return 0;
 118 }