TLA Line data Source code
1 : /*---------------------------------------------------------------------------
2 : *
3 : * Ryu floating-point output for double precision.
4 : *
5 : * Portions Copyright (c) 2018-2023, PostgreSQL Global Development Group
6 : *
7 : * IDENTIFICATION
8 : * src/common/d2s_intrinsics.h
9 : *
10 : * This is a modification of code taken from github.com/ulfjack/ryu under the
11 : * terms of the Boost license (not the Apache license). The original copyright
12 : * notice follows:
13 : *
14 : * Copyright 2018 Ulf Adams
15 : *
16 : * The contents of this file may be used under the terms of the Apache
17 : * License, Version 2.0.
18 : *
19 : * (See accompanying file LICENSE-Apache or copy at
20 : * http://www.apache.org/licenses/LICENSE-2.0)
21 : *
22 : * Alternatively, the contents of this file may be used under the terms of the
23 : * Boost Software License, Version 1.0.
24 : *
25 : * (See accompanying file LICENSE-Boost or copy at
26 : * https://www.boost.org/LICENSE_1_0.txt)
27 : *
28 : * Unless required by applicable law or agreed to in writing, this software is
29 : * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
30 : * KIND, either express or implied.
31 : *
32 : *---------------------------------------------------------------------------
33 : */
34 : #ifndef RYU_D2S_INTRINSICS_H
35 : #define RYU_D2S_INTRINSICS_H
36 :
37 : #if defined(HAS_64_BIT_INTRINSICS)
38 :
39 : #include <intrin.h>
40 :
41 : static inline uint64
42 : umul128(const uint64 a, const uint64 b, uint64 *const productHi)
43 : {
44 : return _umul128(a, b, productHi);
45 : }
46 :
47 : static inline uint64
48 : shiftright128(const uint64 lo, const uint64 hi, const uint32 dist)
49 : {
50 : /*
51 : * For the __shiftright128 intrinsic, the shift value is always modulo 64.
52 : * In the current implementation of the double-precision version of Ryu,
53 : * the shift value is always < 64. (In the case RYU_OPTIMIZE_SIZE == 0,
54 : * the shift value is in the range [49, 58]. Otherwise in the range [2,
55 : * 59].) Check this here in case a future change requires larger shift
56 : * values. In this case this function needs to be adjusted.
57 : */
58 : Assert(dist < 64);
59 : return __shiftright128(lo, hi, (unsigned char) dist);
60 : }
61 :
62 : #else /* defined(HAS_64_BIT_INTRINSICS) */
63 :
64 : static inline uint64
65 : umul128(const uint64 a, const uint64 b, uint64 *const productHi)
66 : {
67 : /*
68 : * The casts here help MSVC to avoid calls to the __allmul library
69 : * function.
70 : */
71 : const uint32 aLo = (uint32) a;
72 : const uint32 aHi = (uint32) (a >> 32);
73 : const uint32 bLo = (uint32) b;
74 : const uint32 bHi = (uint32) (b >> 32);
75 :
76 : const uint64 b00 = (uint64) aLo * bLo;
77 : const uint64 b01 = (uint64) aLo * bHi;
78 : const uint64 b10 = (uint64) aHi * bLo;
79 : const uint64 b11 = (uint64) aHi * bHi;
80 :
81 : const uint32 b00Lo = (uint32) b00;
82 : const uint32 b00Hi = (uint32) (b00 >> 32);
83 :
84 : const uint64 mid1 = b10 + b00Hi;
85 : const uint32 mid1Lo = (uint32) (mid1);
86 : const uint32 mid1Hi = (uint32) (mid1 >> 32);
87 :
88 : const uint64 mid2 = b01 + mid1Lo;
89 : const uint32 mid2Lo = (uint32) (mid2);
90 : const uint32 mid2Hi = (uint32) (mid2 >> 32);
91 :
92 : const uint64 pHi = b11 + mid1Hi + mid2Hi;
93 : const uint64 pLo = ((uint64) mid2Lo << 32) + b00Lo;
94 :
95 : *productHi = pHi;
96 : return pLo;
97 : }
98 :
99 : static inline uint64
100 : shiftright128(const uint64 lo, const uint64 hi, const uint32 dist)
101 : {
102 : /* We don't need to handle the case dist >= 64 here (see above). */
103 : Assert(dist < 64);
104 : #if !defined(RYU_32_BIT_PLATFORM)
105 : Assert(dist > 0);
106 : return (hi << (64 - dist)) | (lo >> dist);
107 : #else
108 : /* Avoid a 64-bit shift by taking advantage of the range of shift values. */
109 : Assert(dist >= 32);
110 : return (hi << (64 - dist)) | ((uint32) (lo >> 32) >> (dist - 32));
111 : #endif
112 : }
113 :
114 : #endif /* // defined(HAS_64_BIT_INTRINSICS) */
115 :
116 : #ifdef RYU_32_BIT_PLATFORM
117 :
118 : /* Returns the high 64 bits of the 128-bit product of a and b. */
119 : static inline uint64
120 : umulh(const uint64 a, const uint64 b)
121 : {
122 : /*
123 : * Reuse the umul128 implementation. Optimizers will likely eliminate the
124 : * instructions used to compute the low part of the product.
125 : */
126 : uint64 hi;
127 :
128 : umul128(a, b, &hi);
129 : return hi;
130 : }
131 :
132 : /*----
133 : * On 32-bit platforms, compilers typically generate calls to library
134 : * functions for 64-bit divisions, even if the divisor is a constant.
135 : *
136 : * E.g.:
137 : * https://bugs.llvm.org/show_bug.cgi?id=37932
138 : * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=17958
139 : * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=37443
140 : *
141 : * The functions here perform division-by-constant using multiplications
142 : * in the same way as 64-bit compilers would do.
143 : *
144 : * NB:
145 : * The multipliers and shift values are the ones generated by clang x64
146 : * for expressions like x/5, x/10, etc.
147 : *----
148 : */
149 :
150 : static inline uint64
151 : div5(const uint64 x)
152 : {
153 : return umulh(x, UINT64CONST(0xCCCCCCCCCCCCCCCD)) >> 2;
154 : }
155 :
156 : static inline uint64
157 : div10(const uint64 x)
158 : {
159 : return umulh(x, UINT64CONST(0xCCCCCCCCCCCCCCCD)) >> 3;
160 : }
161 :
162 : static inline uint64
163 : div100(const uint64 x)
164 : {
165 : return umulh(x >> 2, UINT64CONST(0x28F5C28F5C28F5C3)) >> 2;
166 : }
167 :
168 : static inline uint64
169 : div1e8(const uint64 x)
170 : {
171 : return umulh(x, UINT64CONST(0xABCC77118461CEFD)) >> 26;
172 : }
173 :
174 : #else /* RYU_32_BIT_PLATFORM */
175 :
176 : static inline uint64
177 CBC 3661 : div5(const uint64 x)
178 : {
179 3661 : return x / 5;
180 : }
181 :
182 : static inline uint64
183 12834286 : div10(const uint64 x)
184 : {
185 12834286 : return x / 10;
186 : }
187 :
188 : static inline uint64
189 1844093 : div100(const uint64 x)
190 : {
191 1844093 : return x / 100;
192 : }
193 :
194 : static inline uint64
195 509949 : div1e8(const uint64 x)
196 : {
197 509949 : return x / 100000000;
198 : }
199 :
200 : #endif /* RYU_32_BIT_PLATFORM */
201 :
202 : #endif /* RYU_D2S_INTRINSICS_H */
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