1// Copyright 2018 Ulf Adams
2//
3// The contents of this file may be used under the terms of the Apache License,
4// Version 2.0.
5//
6//    (See accompanying file LICENSE-Apache or copy at
7//     http://www.apache.org/licenses/LICENSE-2.0)
8//
9// Alternatively, the contents of this file may be used under the terms of
10// the Boost Software License, Version 1.0.
11//    (See accompanying file LICENSE-Boost or copy at
12//     https://www.boost.org/LICENSE_1_0.txt)
13//
14// Unless required by applicable law or agreed to in writing, this software
15// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16// KIND, either express or implied.
17#ifndef RYU_F2S_INTRINSICS_H
18#define RYU_F2S_INTRINSICS_H
19
20// Defines RYU_32_BIT_PLATFORM if applicable.
21
22#if defined(RYU_FLOAT_FULL_TABLE)
23
24
25#else
26
27#if defined(RYU_OPTIMIZE_SIZE)
28#else
29#endif
30#define FLOAT_POW5_INV_BITCOUNT (DOUBLE_POW5_INV_BITCOUNT - 64)
31#define FLOAT_POW5_BITCOUNT (DOUBLE_POW5_BITCOUNT - 64)
32
33#endif
34
35static inline uint32_t pow5factor_32(uint32_t value) {
36  uint32_t count = 0;
37  for (;;) {
38    assert(value != 0);
39    const uint32_t q = value / 5;
40    const uint32_t r = value % 5;
41    if (r != 0) {
42      break;
43    }
44    value = q;
45    ++count;
46  }
47  return count;
48}
49
50// Returns true if value is divisible by 5^p.
51static inline bool multipleOfPowerOf5_32(const uint32_t value, const uint32_t p) {
52  return pow5factor_32(value) >= p;
53}
54
55// Returns true if value is divisible by 2^p.
56static inline bool multipleOfPowerOf2_32(const uint32_t value, const uint32_t p) {
57  // __builtin_ctz doesn't appear to be faster here.
58  return (value & ((1u << p) - 1)) == 0;
59}
60
61// It seems to be slightly faster to avoid uint128_t here, although the
62// generated code for uint128_t looks slightly nicer.
63static inline uint32_t mulShift32(const uint32_t m, const uint64_t factor, const int32_t shift) {
64  assert(shift > 32);
65
66  // The casts here help MSVC to avoid calls to the __allmul library
67  // function.
68  const uint32_t factorLo = (uint32_t)(factor);
69  const uint32_t factorHi = (uint32_t)(factor >> 32);
70  const uint64_t bits0 = (uint64_t)m * factorLo;
71  const uint64_t bits1 = (uint64_t)m * factorHi;
72
73#if defined(RYU_32_BIT_PLATFORM)
74  // On 32-bit platforms we can avoid a 64-bit shift-right since we only
75  // need the upper 32 bits of the result and the shift value is > 32.
76  const uint32_t bits0Hi = (uint32_t)(bits0 >> 32);
77  uint32_t bits1Lo = (uint32_t)(bits1);
78  uint32_t bits1Hi = (uint32_t)(bits1 >> 32);
79  bits1Lo += bits0Hi;
80  bits1Hi += (bits1Lo < bits0Hi);
81  if (shift >= 64) {
82    // s2f can call this with a shift value >= 64, which we have to handle.
83    // This could now be slower than the !defined(RYU_32_BIT_PLATFORM) case.
84    return (uint32_t)(bits1Hi >> (shift - 64));
85  } else {
86    const int32_t s = shift - 32;
87    return (bits1Hi << (32 - s)) | (bits1Lo >> s);
88  }
89#else // RYU_32_BIT_PLATFORM
90  const uint64_t sum = (bits0 >> 32) + bits1;
91  const uint64_t shiftedSum = sum >> (shift - 32);
92  assert(shiftedSum <= UINT32_MAX);
93  return (uint32_t) shiftedSum;
94#endif // RYU_32_BIT_PLATFORM
95}
96
97static inline uint32_t mulPow5InvDivPow2(const uint32_t m, const uint32_t q, const int32_t j) {
98#if defined(RYU_FLOAT_FULL_TABLE)
99  return mulShift32(m, FLOAT_POW5_INV_SPLIT[q], j);
100#elif defined(RYU_OPTIMIZE_SIZE)
101  // The inverse multipliers are defined as [2^x / 5^y] + 1; the upper 64 bits from the double lookup
102  // table are the correct bits for [2^x / 5^y], so we have to add 1 here. Note that we rely on the
103  // fact that the added 1 that's already stored in the table never overflows into the upper 64 bits.
104  uint64_t pow5[2];
105  double_computeInvPow5(q, pow5);
106  return mulShift32(m, pow5[1] + 1, j);
107#else
108  return mulShift32(m, DOUBLE_POW5_INV_SPLIT[q][1] + 1, j);
109#endif
110}
111
112static inline uint32_t mulPow5divPow2(const uint32_t m, const uint32_t i, const int32_t j) {
113#if defined(RYU_FLOAT_FULL_TABLE)
114  return mulShift32(m, FLOAT_POW5_SPLIT[i], j);
115#elif defined(RYU_OPTIMIZE_SIZE)
116  uint64_t pow5[2];
117  double_computePow5(i, pow5);
118  return mulShift32(m, pow5[1], j);
119#else
120  return mulShift32(m, DOUBLE_POW5_SPLIT[i][1], j);
121#endif
122}
123
124#endif // RYU_F2S_INTRINSICS_H
125