qemu/tests/fp/fp-test-log2.c
Richard Henderson 2fa3546c8f softfloat: Move floatN_log2 to softfloat-parts.c.inc
Rename to parts$N_log2.  Though this is partly a ruse, since I do not
believe the code will succeed for float128 without work.  Which is ok
for now, because we do not need this for more than float32 and float64.

Since berkeley-testfloat-3 doesn't support log2, compare float64_log2
vs the system log2.  Fix the errors for inputs near 1.0:

test: 3ff00000000000b0  +0x1.00000000000b0p+0
  sf: 3d2fa00000000000  +0x1.fa00000000000p-45
libm: 3d2fbd422b1bd36f  +0x1.fbd422b1bd36fp-45
Error in fraction: 32170028290927 ulp

test: 3feec24f6770b100  +0x1.ec24f6770b100p-1
  sf: bfad3740d13c9ec0  -0x1.d3740d13c9ec0p-5
libm: bfad3740d13c9e98  -0x1.d3740d13c9e98p-5
Error in fraction: 40 ulp

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2021-06-03 14:09:02 -07:00

119 lines
2.7 KiB
C

/*
* fp-test-log2.c - test QEMU's softfloat log2
*
* Copyright (C) 2020, Linaro, Ltd.
*
* License: GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef HW_POISON_H
#error Must define HW_POISON_H to work around TARGET_* poisoning
#endif
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include <math.h>
#include "fpu/softfloat.h"
typedef union {
double d;
float64 i;
} ufloat64;
static int errors;
static void compare(ufloat64 test, ufloat64 real, ufloat64 soft, bool exact)
{
int msb;
uint64_t ulp = UINT64_MAX;
if (real.i == soft.i) {
return;
}
msb = 63 - __builtin_clzll(real.i ^ soft.i);
if (msb < 52) {
if (real.i > soft.i) {
ulp = real.i - soft.i;
} else {
ulp = soft.i - real.i;
}
}
/* glibc allows 3 ulp error in its libm-test-ulps; allow 4 here */
if (!exact && ulp <= 4) {
return;
}
printf("test: %016" PRIx64 " %+.13a\n"
" sf: %016" PRIx64 " %+.13a\n"
"libm: %016" PRIx64 " %+.13a\n",
test.i, test.d, soft.i, soft.d, real.i, real.d);
if (msb == 63) {
printf("Error in sign!\n\n");
} else if (msb >= 52) {
printf("Error in exponent: %d\n\n",
(int)(soft.i >> 52) - (int)(real.i >> 52));
} else {
printf("Error in fraction: %" PRIu64 " ulp\n\n", ulp);
}
if (++errors == 20) {
exit(1);
}
}
int main(int ac, char **av)
{
ufloat64 test, real, soft;
float_status qsf = {0};
int i;
set_float_rounding_mode(float_round_nearest_even, &qsf);
test.d = 0.0;
real.d = -__builtin_inf();
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, true);
test.d = 1.0;
real.d = 0.0;
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, true);
test.d = 2.0;
real.d = 1.0;
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, true);
test.d = 4.0;
real.d = 2.0;
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, true);
test.d = 0x1p64;
real.d = 64.0;
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, true);
test.d = __builtin_inf();
real.d = __builtin_inf();
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, true);
for (i = 0; i < 10000; ++i) {
test.d = drand48() + 1.0; /* [1.0, 2.0) */
real.d = log2(test.d);
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, false);
test.d = drand48() * 100; /* [0.0, 100) */
real.d = log2(test.d);
soft.i = float64_log2(test.i, &qsf);
compare(test, real, soft, false);
}
return 0;
}