1/*
2 * Copyright (c) 2015 Advanced Micro Devices, Inc.
3 * Copyright (c) 2016 Aaron Watry
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a copy
6 * of this software and associated documentation files (the "Software"), to deal
7 * in the Software without restriction, including without limitation the rights
8 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 * copies of the Software, and to permit persons to whom the Software is
10 * furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 * THE SOFTWARE.
22 */
23
24#include <clc/clc.h>
25#include "../clcmacro.h"
26#include "math.h"
27
28_CLC_OVERLOAD _CLC_DEF int ilogb(float x) {
29    uint ux = as_uint(x);
30    uint ax = ux & EXSIGNBIT_SP32;
31    int rs = -118 - (int) clz(ux & MANTBITS_SP32);
32    int r = (int) (ax >> EXPSHIFTBITS_SP32) - EXPBIAS_SP32;
33    r = ax < 0x00800000U ? rs : r;
34    r = ax == 0 ? FP_ILOGB0 : r;
35
36    // We could merge those 2 tests and have:
37    //
38    //    r = ax >= EXPBITS_SP32 ? 0x7fffffff : r
39    //
40    // since FP_ILOGBNAN is set to INT_MAX, but it's clearer this way and
41    // FP_ILOGBNAN can change without requiring changes to ilogb() code.
42    r = ax > EXPBITS_SP32 ? FP_ILOGBNAN : r;
43    r = ax == EXPBITS_SP32 ? 0x7fffffff : r;
44    return r;
45}
46
47_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, int, ilogb, float);
48
49#ifdef cl_khr_fp64
50#pragma OPENCL EXTENSION cl_khr_fp64 : enable
51
52_CLC_OVERLOAD _CLC_DEF int ilogb(double x) {
53    ulong ux = as_ulong(x);
54    ulong ax = ux & ~SIGNBIT_DP64;
55    int r = (int) (ax >> EXPSHIFTBITS_DP64) - EXPBIAS_DP64;
56    int rs = -1011 - (int) clz(ax & MANTBITS_DP64);
57    r = ax < 0x0010000000000000UL ? rs : r;
58    r = ax == 0UL ? FP_ILOGB0 : r;
59
60    // We could merge those 2 tests and have:
61    //
62    //    r = ax >= 0x7ff0000000000000UL ? 0x7fffffff : r
63    //
64    // since FP_ILOGBNAN is set to INT_MAX, but it's clearer this way and
65    // FP_ILOGBNAN can change without requiring changes to ilogb() code.
66    r = ax > 0x7ff0000000000000UL ? FP_ILOGBNAN : r;
67    r = ax == 0x7ff0000000000000UL ? 0x7fffffff : r;
68    return r;
69}
70
71_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, int, ilogb, double);
72
73#endif // cl_khr_fp64
74