1// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
2// for details. All rights reserved. Use of this source code is governed by a
3// BSD-style license that can be found in the LICENSE file.
4
5#include "platform/globals.h" // NOLINT
6
7#if defined(TARGET_ARCH_ARM)
8
9#include "vm/constants.h" // NOLINT
10
11namespace dart {
12
13using dart::bit_cast;
14
15const char* cpu_reg_names[kNumberOfCpuRegisters] = {
16 "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
17 "r8", "ctx", "pp", "fp", "ip", "sp", "lr", "pc",
18};
19
20const char* fpu_reg_names[kNumberOfFpuRegisters] = {
21 "q0", "q1", "q2", "q3", "q4", "q5", "q6", "q7",
22#if defined(VFPv3_D32)
23 "q8", "q9", "q10", "q11", "q12", "q13", "q14", "q15",
24#endif
25};
26const char* fpu_d_reg_names[kNumberOfDRegisters] = {
27 "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7",
28 "d8", "d9", "d10", "d11", "d12", "d13", "d14", "d15",
29#if defined(VFPv3_D32)
30 "d16", "d17", "d18", "d19", "d20", "d21", "d22", "d23",
31 "d24", "d25", "d26", "d27", "d28", "d29", "d30", "d31",
32#endif
33};
34const char* fpu_s_reg_names[kNumberOfSRegisters] = {
35 "s0", "s1", "s2", "s3", "s4", "s5", "s6", "s7", "s8", "s9", "s10",
36 "s11", "s12", "s13", "s14", "s15", "s16", "s17", "s18", "s19", "s20", "s21",
37 "s22", "s23", "s24", "s25", "s26", "s27", "s28", "s29", "s30", "s31",
38};
39
40const Register CallingConventions::ArgumentRegisters[] = {R0, R1, R2, R3};
41
42const FpuRegister CallingConventions::FpuArgumentRegisters[] = {Q0, Q1, Q2, Q3};
43const DRegister CallingConventions::FpuDArgumentRegisters[] = {D0, D1, D2, D3,
44 D4, D5, D6, D7};
45const SRegister CallingConventions::FpuSArgumentRegisters[] = {
46 S0, S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15};
47
48float ReciprocalEstimate(float a) {
49 // From the ARM Architecture Reference Manual A2-85.
50 if (isinf(a) || (fabs(a) >= exp2f(126)))
51 return a >= 0.0f ? 0.0f : -0.0f;
52 else if (a == 0.0f)
53 return 1.0f / a;
54 else if (isnan(a))
55 return a;
56
57 uint32_t a_bits = bit_cast<uint32_t, float>(a);
58 // scaled = '0011 1111 1110' : a<22:0> : Zeros(29)
59 uint64_t scaled = (static_cast<uint64_t>(0x3fe) << 52) |
60 ((static_cast<uint64_t>(a_bits) & 0x7fffff) << 29);
61 // result_exp = 253 - UInt(a<30:23>)
62 int32_t result_exp = 253 - ((a_bits >> 23) & 0xff);
63 ASSERT((result_exp >= 1) && (result_exp <= 252));
64
65 double scaled_d = bit_cast<double, uint64_t>(scaled);
66 ASSERT((scaled_d >= 0.5) && (scaled_d < 1.0));
67
68 // a in units of 1/512 rounded down.
69 int32_t q = static_cast<int32_t>(scaled_d * 512.0);
70 // reciprocal r.
71 double r = 1.0 / ((static_cast<double>(q) + 0.5) / 512.0);
72 // r in units of 1/256 rounded to nearest.
73 int32_t s = static_cast<int32_t>(256.0 * r + 0.5);
74 double estimate = static_cast<double>(s) / 256.0;
75 ASSERT((estimate >= 1.0) && (estimate <= (511.0 / 256.0)));
76
77 // result = sign : result_exp<7:0> : estimate<51:29>
78 int32_t result_bits =
79 (a_bits & 0x80000000) | ((result_exp & 0xff) << 23) |
80 ((bit_cast<uint64_t, double>(estimate) >> 29) & 0x7fffff);
81 return bit_cast<float, int32_t>(result_bits);
82}
83
84float ReciprocalStep(float op1, float op2) {
85 float p;
86 if ((isinf(op1) && op2 == 0.0f) || (op1 == 0.0f && isinf(op2))) {
87 p = 0.0f;
88 } else {
89 p = op1 * op2;
90 }
91 return 2.0f - p;
92}
93
94float ReciprocalSqrtEstimate(float a) {
95 // From the ARM Architecture Reference Manual A2-87.
96 if (a < 0.0f)
97 return NAN;
98 else if (isinf(a) || (fabs(a) >= exp2f(126)))
99 return 0.0f;
100 else if (a == 0.0)
101 return 1.0f / a;
102 else if (isnan(a))
103 return a;
104
105 uint32_t a_bits = bit_cast<uint32_t, float>(a);
106 uint64_t scaled;
107 if (((a_bits >> 23) & 1) != 0) {
108 // scaled = '0 01111111101' : operand<22:0> : Zeros(29)
109 scaled = (static_cast<uint64_t>(0x3fd) << 52) |
110 ((static_cast<uint64_t>(a_bits) & 0x7fffff) << 29);
111 } else {
112 // scaled = '0 01111111110' : operand<22:0> : Zeros(29)
113 scaled = (static_cast<uint64_t>(0x3fe) << 52) |
114 ((static_cast<uint64_t>(a_bits) & 0x7fffff) << 29);
115 }
116 // result_exp = (380 - UInt(operand<30:23>) DIV 2;
117 int32_t result_exp = (380 - ((a_bits >> 23) & 0xff)) / 2;
118
119 double scaled_d = bit_cast<double, uint64_t>(scaled);
120 ASSERT((scaled_d >= 0.25) && (scaled_d < 1.0));
121
122 double r;
123 if (scaled_d < 0.5) {
124 // range 0.25 <= a < 0.5
125
126 // a in units of 1/512 rounded down.
127 int32_t q0 = static_cast<int32_t>(scaled_d * 512.0);
128 // reciprocal root r.
129 r = 1.0 / sqrt((static_cast<double>(q0) + 0.5) / 512.0);
130 } else {
131 // range 0.5 <= a < 1.0
132
133 // a in units of 1/256 rounded down.
134 int32_t q1 = static_cast<int32_t>(scaled_d * 256.0);
135 // reciprocal root r.
136 r = 1.0 / sqrt((static_cast<double>(q1) + 0.5) / 256.0);
137 }
138 // r in units of 1/256 rounded to nearest.
139 int32_t s = static_cast<int>(256.0 * r + 0.5);
140 double estimate = static_cast<double>(s) / 256.0;
141 ASSERT((estimate >= 1.0) && (estimate <= (511.0 / 256.0)));
142
143 // result = 0 : result_exp<7:0> : estimate<51:29>
144 int32_t result_bits =
145 ((result_exp & 0xff) << 23) |
146 ((bit_cast<uint64_t, double>(estimate) >> 29) & 0x7fffff);
147 return bit_cast<float, int32_t>(result_bits);
148}
149
150float ReciprocalSqrtStep(float op1, float op2) {
151 float p;
152 if ((isinf(op1) && op2 == 0.0f) || (op1 == 0.0f && isinf(op2))) {
153 p = 0.0f;
154 } else {
155 p = op1 * op2;
156 }
157 return (3.0f - p) / 2.0f;
158}
159
160} // namespace dart
161
162#endif // defined(TARGET_ARCH_ARM)
163