1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 // Check all examples from table 10-1 of "Hacker's Delight".
6
7 #include "src/base/division-by-constant.h"
8
9 #include <stdint.h>
10
11 #include <ostream> // NOLINT
12
13 #include "testing/gtest-support.h"
14
15 namespace v8 {
16 namespace base {
17
18 template <class T>
operator <<(std::ostream & os,const MagicNumbersForDivision<T> & mag)19 std::ostream& operator<<(std::ostream& os,
20 const MagicNumbersForDivision<T>& mag) {
21 return os << "{ multiplier: " << mag.multiplier << ", shift: " << mag.shift
22 << ", add: " << mag.add << " }";
23 }
24
25
26 // Some abbreviations...
27
28 typedef MagicNumbersForDivision<uint32_t> M32;
29 typedef MagicNumbersForDivision<uint64_t> M64;
30
31
s32(int32_t d)32 static M32 s32(int32_t d) {
33 return SignedDivisionByConstant<uint32_t>(static_cast<uint32_t>(d));
34 }
35
36
s64(int64_t d)37 static M64 s64(int64_t d) {
38 return SignedDivisionByConstant<uint64_t>(static_cast<uint64_t>(d));
39 }
40
41
u32(uint32_t d)42 static M32 u32(uint32_t d) { return UnsignedDivisionByConstant<uint32_t>(d); }
u64(uint64_t d)43 static M64 u64(uint64_t d) { return UnsignedDivisionByConstant<uint64_t>(d); }
44
45
TEST(DivisionByConstant,Signed32)46 TEST(DivisionByConstant, Signed32) {
47 EXPECT_EQ(M32(0x99999999U, 1, false), s32(-5));
48 EXPECT_EQ(M32(0x55555555U, 1, false), s32(-3));
49 int32_t d = -1;
50 for (unsigned k = 1; k <= 32 - 1; ++k) {
51 d *= 2;
52 EXPECT_EQ(M32(0x7FFFFFFFU, k - 1, false), s32(d));
53 }
54 for (unsigned k = 1; k <= 32 - 2; ++k) {
55 EXPECT_EQ(M32(0x80000001U, k - 1, false), s32(1 << k));
56 }
57 EXPECT_EQ(M32(0x55555556U, 0, false), s32(3));
58 EXPECT_EQ(M32(0x66666667U, 1, false), s32(5));
59 EXPECT_EQ(M32(0x2AAAAAABU, 0, false), s32(6));
60 EXPECT_EQ(M32(0x92492493U, 2, false), s32(7));
61 EXPECT_EQ(M32(0x38E38E39U, 1, false), s32(9));
62 EXPECT_EQ(M32(0x66666667U, 2, false), s32(10));
63 EXPECT_EQ(M32(0x2E8BA2E9U, 1, false), s32(11));
64 EXPECT_EQ(M32(0x2AAAAAABU, 1, false), s32(12));
65 EXPECT_EQ(M32(0x51EB851FU, 3, false), s32(25));
66 EXPECT_EQ(M32(0x10624DD3U, 3, false), s32(125));
67 EXPECT_EQ(M32(0x68DB8BADU, 8, false), s32(625));
68 }
69
70
TEST(DivisionByConstant,Unsigned32)71 TEST(DivisionByConstant, Unsigned32) {
72 EXPECT_EQ(M32(0x00000000U, 0, true), u32(1));
73 for (unsigned k = 1; k <= 30; ++k) {
74 EXPECT_EQ(M32(1U << (32 - k), 0, false), u32(1U << k));
75 }
76 EXPECT_EQ(M32(0xAAAAAAABU, 1, false), u32(3));
77 EXPECT_EQ(M32(0xCCCCCCCDU, 2, false), u32(5));
78 EXPECT_EQ(M32(0xAAAAAAABU, 2, false), u32(6));
79 EXPECT_EQ(M32(0x24924925U, 3, true), u32(7));
80 EXPECT_EQ(M32(0x38E38E39U, 1, false), u32(9));
81 EXPECT_EQ(M32(0xCCCCCCCDU, 3, false), u32(10));
82 EXPECT_EQ(M32(0xBA2E8BA3U, 3, false), u32(11));
83 EXPECT_EQ(M32(0xAAAAAAABU, 3, false), u32(12));
84 EXPECT_EQ(M32(0x51EB851FU, 3, false), u32(25));
85 EXPECT_EQ(M32(0x10624DD3U, 3, false), u32(125));
86 EXPECT_EQ(M32(0xD1B71759U, 9, false), u32(625));
87 }
88
89
TEST(DivisionByConstant,Signed64)90 TEST(DivisionByConstant, Signed64) {
91 EXPECT_EQ(M64(0x9999999999999999ULL, 1, false), s64(-5));
92 EXPECT_EQ(M64(0x5555555555555555ULL, 1, false), s64(-3));
93 int64_t d = -1;
94 for (unsigned k = 1; k <= 64 - 1; ++k) {
95 d *= 2;
96 EXPECT_EQ(M64(0x7FFFFFFFFFFFFFFFULL, k - 1, false), s64(d));
97 }
98 for (unsigned k = 1; k <= 64 - 2; ++k) {
99 EXPECT_EQ(M64(0x8000000000000001ULL, k - 1, false), s64(1LL << k));
100 }
101 EXPECT_EQ(M64(0x5555555555555556ULL, 0, false), s64(3));
102 EXPECT_EQ(M64(0x6666666666666667ULL, 1, false), s64(5));
103 EXPECT_EQ(M64(0x2AAAAAAAAAAAAAABULL, 0, false), s64(6));
104 EXPECT_EQ(M64(0x4924924924924925ULL, 1, false), s64(7));
105 EXPECT_EQ(M64(0x1C71C71C71C71C72ULL, 0, false), s64(9));
106 EXPECT_EQ(M64(0x6666666666666667ULL, 2, false), s64(10));
107 EXPECT_EQ(M64(0x2E8BA2E8BA2E8BA3ULL, 1, false), s64(11));
108 EXPECT_EQ(M64(0x2AAAAAAAAAAAAAABULL, 1, false), s64(12));
109 EXPECT_EQ(M64(0xA3D70A3D70A3D70BULL, 4, false), s64(25));
110 EXPECT_EQ(M64(0x20C49BA5E353F7CFULL, 4, false), s64(125));
111 EXPECT_EQ(M64(0x346DC5D63886594BULL, 7, false), s64(625));
112 }
113
114
TEST(DivisionByConstant,Unsigned64)115 TEST(DivisionByConstant, Unsigned64) {
116 EXPECT_EQ(M64(0x0000000000000000ULL, 0, true), u64(1));
117 for (unsigned k = 1; k <= 64 - 2; ++k) {
118 EXPECT_EQ(M64(1ULL << (64 - k), 0, false), u64(1ULL << k));
119 }
120 EXPECT_EQ(M64(0xAAAAAAAAAAAAAAABULL, 1, false), u64(3));
121 EXPECT_EQ(M64(0xCCCCCCCCCCCCCCCDULL, 2, false), u64(5));
122 EXPECT_EQ(M64(0xAAAAAAAAAAAAAAABULL, 2, false), u64(6));
123 EXPECT_EQ(M64(0x2492492492492493ULL, 3, true), u64(7));
124 EXPECT_EQ(M64(0xE38E38E38E38E38FULL, 3, false), u64(9));
125 EXPECT_EQ(M64(0xCCCCCCCCCCCCCCCDULL, 3, false), u64(10));
126 EXPECT_EQ(M64(0x2E8BA2E8BA2E8BA3ULL, 1, false), u64(11));
127 EXPECT_EQ(M64(0xAAAAAAAAAAAAAAABULL, 3, false), u64(12));
128 EXPECT_EQ(M64(0x47AE147AE147AE15ULL, 5, true), u64(25));
129 EXPECT_EQ(M64(0x0624DD2F1A9FBE77ULL, 7, true), u64(125));
130 EXPECT_EQ(M64(0x346DC5D63886594BULL, 7, false), u64(625));
131 }
132
133 } // namespace base
134 } // namespace v8
135