1 /* Test of rounding towards negative infinity.
2 Copyright (C) 2007-2010 Free Software Foundation, Inc.
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
17 /* Written by Bruno Haible <bruno@clisp.org>, 2007. */
19 /* When this test fails on some platform, build it together with the gnulib
20 module 'fprintf-posix' for optimal debugging output. */
31 #include "isnanf-nolibm.h"
35 /* The reference implementation, taken from lib/floor.c. */
38 #define MANT_DIG FLT_MANT_DIG
39 #define L_(literal) literal##f
42 static const DOUBLE TWO_MANT_DIG =
43 /* Assume MANT_DIG <= 5 * 31.
45 n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
46 (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
47 * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
48 * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
49 * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
50 * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
53 floorf_reference (DOUBLE x)
55 /* The use of 'volatile' guarantees that excess precision bits are dropped
56 at each addition step and before the following comparison at the caller's
57 site. It is necessary on x86 systems where double-floats are not IEEE
58 compliant by default, to avoid that the results become platform and compiler
59 option dependent. 'volatile' is a portable alternative to gcc's
60 -ffloat-store option. */
61 volatile DOUBLE y = x;
62 volatile DOUBLE z = y;
66 /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1. */
69 /* Round to the next integer (nearest or up or down, doesn't matter). */
72 /* Enforce rounding down. */
79 /* Work around ICC's desire to optimize denormal floats to 0. */
82 /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */
83 if (z > - TWO_MANT_DIG)
85 /* Round to the next integer (nearest or up or down, doesn't matter). */
88 /* Enforce rounding down. */
97 /* Test for equality. */
99 equal (DOUBLE x, DOUBLE y)
101 return (isnanf (x) ? isnanf (y) : x == y);
104 /* Test whether the result for a given argument is correct. */
106 correct_result_p (DOUBLE x, DOUBLE result)
109 (x < 0 && x >= -1 ? result == - L_(1.0) :
110 x - 1 < x ? result <= x && result >= x - 1 && x - result < 1 :
114 /* Test the function for a given argument. */
118 /* If the reference implementation is incorrect, bail out immediately. */
119 float reference = floorf_reference (x);
120 ASSERT (correct_result_p (x, reference));
121 /* If the actual implementation is wrong, return an error code. */
123 float result = floorf (x);
124 if (correct_result_p (x, result))
128 #if GNULIB_TEST_FPRINTF_POSIX
129 fprintf (stderr, "floorf %g(%a) = %g(%a) or %g(%a)?\n",
130 x, x, reference, reference, result, result);
137 #define NUM_HIGHBITS 12
138 #define NUM_LOWBITS 4
143 unsigned int highbits;
144 unsigned int lowbits;
146 for (highbits = 0; highbits < (1 << NUM_HIGHBITS); highbits++)
147 for (lowbits = 0; lowbits < (1 << NUM_LOWBITS); lowbits++)
149 /* Combine highbits and lowbits into a floating-point number,
150 sign-extending the lowbits to 32-NUM_HIGHBITS bits. */
151 union { float f; uint32_t i; } janus;
152 janus.i = ((uint32_t) highbits << (32 - NUM_HIGHBITS))
153 | ((uint32_t) ((int32_t) ((uint32_t) lowbits << (32 - NUM_LOWBITS))
154 >> (32 - NUM_LOWBITS - NUM_HIGHBITS))
156 error |= check (janus.f);
158 return (error ? 1 : 0);