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2fa3546c8f
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>
119 lines
2.7 KiB
C
119 lines
2.7 KiB
C
/*
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* fp-test-log2.c - test QEMU's softfloat log2
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*
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* Copyright (C) 2020, Linaro, Ltd.
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*
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* License: GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef HW_POISON_H
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#error Must define HW_POISON_H to work around TARGET_* poisoning
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#endif
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#include "qemu/osdep.h"
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#include "qemu/cutils.h"
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#include <math.h>
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#include "fpu/softfloat.h"
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typedef union {
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double d;
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float64 i;
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} ufloat64;
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static int errors;
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static void compare(ufloat64 test, ufloat64 real, ufloat64 soft, bool exact)
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{
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int msb;
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uint64_t ulp = UINT64_MAX;
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if (real.i == soft.i) {
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return;
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}
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msb = 63 - __builtin_clzll(real.i ^ soft.i);
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if (msb < 52) {
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if (real.i > soft.i) {
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ulp = real.i - soft.i;
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} else {
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ulp = soft.i - real.i;
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}
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}
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/* glibc allows 3 ulp error in its libm-test-ulps; allow 4 here */
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if (!exact && ulp <= 4) {
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return;
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}
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printf("test: %016" PRIx64 " %+.13a\n"
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" sf: %016" PRIx64 " %+.13a\n"
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"libm: %016" PRIx64 " %+.13a\n",
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test.i, test.d, soft.i, soft.d, real.i, real.d);
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if (msb == 63) {
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printf("Error in sign!\n\n");
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} else if (msb >= 52) {
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printf("Error in exponent: %d\n\n",
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(int)(soft.i >> 52) - (int)(real.i >> 52));
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} else {
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printf("Error in fraction: %" PRIu64 " ulp\n\n", ulp);
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}
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if (++errors == 20) {
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exit(1);
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}
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}
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int main(int ac, char **av)
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{
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ufloat64 test, real, soft;
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float_status qsf = {0};
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int i;
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set_float_rounding_mode(float_round_nearest_even, &qsf);
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test.d = 0.0;
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real.d = -__builtin_inf();
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, true);
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test.d = 1.0;
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real.d = 0.0;
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, true);
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test.d = 2.0;
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real.d = 1.0;
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, true);
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test.d = 4.0;
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real.d = 2.0;
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, true);
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test.d = 0x1p64;
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real.d = 64.0;
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, true);
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test.d = __builtin_inf();
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real.d = __builtin_inf();
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, true);
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for (i = 0; i < 10000; ++i) {
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test.d = drand48() + 1.0; /* [1.0, 2.0) */
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real.d = log2(test.d);
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, false);
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test.d = drand48() * 100; /* [0.0, 100) */
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real.d = log2(test.d);
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soft.i = float64_log2(test.i, &qsf);
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compare(test, real, soft, false);
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}
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return 0;
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}
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