1 //===- darwin-aarch64 floating point env manipulation functions -*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_AARCH64_FENV_DARWIN_IMPL_H
10 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_AARCH64_FENV_DARWIN_IMPL_H
11
12 #include "src/__support/macros/attributes.h" // LIBC_INLINE
13 #include "src/__support/macros/config.h"
14 #include "src/__support/macros/properties/architectures.h"
15
16 #if !defined(LIBC_TARGET_ARCH_IS_AARCH64) || !defined(__APPLE__)
17 #error "Invalid include"
18 #endif
19
20 #include <arm_acle.h>
21 #include <stdint.h>
22
23 #include "hdr/fenv_macros.h"
24 #include "hdr/types/fenv_t.h"
25 #include "src/__support/FPUtil/FPBits.h"
26
27 namespace LIBC_NAMESPACE_DECL {
28 namespace fputil {
29
30 struct FEnv {
31 struct FPState {
32 uint64_t StatusWord;
33 uint64_t ControlWord;
34 };
35
36 static_assert(
37 sizeof(fenv_t) == sizeof(FPState),
38 "Internal floating point state does not match the public fenv_t type.");
39
40 static constexpr uint32_t TONEAREST = 0x0;
41 static constexpr uint32_t UPWARD = 0x1;
42 static constexpr uint32_t DOWNWARD = 0x2;
43 static constexpr uint32_t TOWARDZERO = 0x3;
44
45 // These will be the exception flags we use for exception values normalized
46 // from both status word and control word.
47 // We add EX_ prefix to the names since macOS <math.h> defines OVERFLOW and
48 // UNDERFLOW macros.
49 static constexpr uint32_t EX_INVALID = 0x1;
50 static constexpr uint32_t EX_DIVBYZERO = 0x2;
51 static constexpr uint32_t EX_OVERFLOW = 0x4;
52 static constexpr uint32_t EX_UNDERFLOW = 0x8;
53 static constexpr uint32_t EX_INEXACT = 0x10;
54 // __APPLE__ ARM64 has an extra flag that is raised when a denormal is flushed
55 // to zero.
56 static constexpr uint32_t EX_FLUSHTOZERO = 0x20;
57
58 // Zero-th bit is the first bit.
59 static constexpr uint32_t ROUNDING_CONTROL_BIT_POSITION = 22;
60
61 // In addition to the 5 floating point exceptions, macOS on arm64 defines
62 // another floating point exception: FE_FLUSHTOZERO, which is controlled by
63 // __fpcr_flush_to_zero bit in the FPCR register. This control bit is
64 // located in a different place from FE_FLUSHTOZERO status bit relative to
65 // the other exceptions.
exception_value_from_statusFEnv66 LIBC_INLINE static uint32_t exception_value_from_status(int status) {
67 return ((status & FE_INVALID) ? EX_INVALID : 0) |
68 ((status & FE_DIVBYZERO) ? EX_DIVBYZERO : 0) |
69 ((status & FE_OVERFLOW) ? EX_OVERFLOW : 0) |
70 ((status & FE_UNDERFLOW) ? EX_UNDERFLOW : 0) |
71 ((status & FE_INEXACT) ? EX_INEXACT : 0) |
72 ((status & FE_FLUSHTOZERO) ? EX_FLUSHTOZERO : 0);
73 }
74
exception_value_from_controlFEnv75 LIBC_INLINE static uint32_t exception_value_from_control(int control) {
76 return ((control & __fpcr_trap_invalid) ? EX_INVALID : 0) |
77 ((control & __fpcr_trap_divbyzero) ? EX_DIVBYZERO : 0) |
78 ((control & __fpcr_trap_overflow) ? EX_OVERFLOW : 0) |
79 ((control & __fpcr_trap_underflow) ? EX_UNDERFLOW : 0) |
80 ((control & __fpcr_trap_inexact) ? EX_INEXACT : 0) |
81 ((control & __fpcr_flush_to_zero) ? EX_FLUSHTOZERO : 0);
82 }
83
exception_value_to_statusFEnv84 LIBC_INLINE static int exception_value_to_status(uint32_t excepts) {
85 return ((excepts & EX_INVALID) ? FE_INVALID : 0) |
86 ((excepts & EX_DIVBYZERO) ? FE_DIVBYZERO : 0) |
87 ((excepts & EX_OVERFLOW) ? FE_OVERFLOW : 0) |
88 ((excepts & EX_UNDERFLOW) ? FE_UNDERFLOW : 0) |
89 ((excepts & EX_INEXACT) ? FE_INEXACT : 0) |
90 ((excepts & EX_FLUSHTOZERO) ? FE_FLUSHTOZERO : 0);
91 }
92
exception_value_to_controlFEnv93 LIBC_INLINE static int exception_value_to_control(uint32_t excepts) {
94 return ((excepts & EX_INVALID) ? __fpcr_trap_invalid : 0) |
95 ((excepts & EX_DIVBYZERO) ? __fpcr_trap_divbyzero : 0) |
96 ((excepts & EX_OVERFLOW) ? __fpcr_trap_overflow : 0) |
97 ((excepts & EX_UNDERFLOW) ? __fpcr_trap_underflow : 0) |
98 ((excepts & EX_INEXACT) ? __fpcr_trap_inexact : 0) |
99 ((excepts & EX_FLUSHTOZERO) ? __fpcr_flush_to_zero : 0);
100 }
101
get_control_wordFEnv102 LIBC_INLINE static uint32_t get_control_word() { return __arm_rsr("fpcr"); }
103
set_control_wordFEnv104 LIBC_INLINE static void set_control_word(uint32_t fpcr) {
105 __arm_wsr("fpcr", fpcr);
106 }
107
get_status_wordFEnv108 LIBC_INLINE static uint32_t get_status_word() { return __arm_rsr("fpsr"); }
109
set_status_wordFEnv110 LIBC_INLINE static void set_status_word(uint32_t fpsr) {
111 __arm_wsr("fpsr", fpsr);
112 }
113 };
114
enable_except(int excepts)115 LIBC_INLINE int enable_except(int excepts) {
116 uint32_t new_excepts = FEnv::exception_value_from_status(excepts);
117 uint32_t control_word = FEnv::get_control_word();
118 uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
119 if (new_excepts != old_excepts) {
120 control_word |= FEnv::exception_value_to_control(new_excepts);
121 FEnv::set_control_word(control_word);
122 }
123 return FEnv::exception_value_to_status(old_excepts);
124 }
125
disable_except(int excepts)126 LIBC_INLINE int disable_except(int excepts) {
127 uint32_t disabled_excepts = FEnv::exception_value_from_status(excepts);
128 uint32_t control_word = FEnv::get_control_word();
129 uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
130 control_word &= ~FEnv::exception_value_to_control(disabled_excepts);
131 FEnv::set_control_word(control_word);
132 return FEnv::exception_value_to_status(old_excepts);
133 }
134
get_except()135 LIBC_INLINE int get_except() {
136 uint32_t control_word = FEnv::get_control_word();
137 uint32_t enabled_excepts = FEnv::exception_value_from_control(control_word);
138 return FEnv::exception_value_to_status(enabled_excepts);
139 }
140
clear_except(int excepts)141 LIBC_INLINE int clear_except(int excepts) {
142 uint32_t status_word = FEnv::get_status_word();
143 uint32_t except_value = FEnv::exception_value_from_status(excepts);
144 status_word &= ~FEnv::exception_value_to_status(except_value);
145 FEnv::set_status_word(status_word);
146 return 0;
147 }
148
test_except(int excepts)149 LIBC_INLINE int test_except(int excepts) {
150 uint32_t statusWord = FEnv::get_status_word();
151 uint32_t ex_value = FEnv::exception_value_from_status(excepts);
152 return statusWord & FEnv::exception_value_to_status(ex_value);
153 }
154
set_except(int excepts)155 LIBC_INLINE int set_except(int excepts) {
156 uint32_t status_word = FEnv::get_status_word();
157 uint32_t new_exceptions = FEnv::exception_value_from_status(excepts);
158 status_word |= FEnv::exception_value_to_status(new_exceptions);
159 FEnv::set_status_word(status_word);
160 return 0;
161 }
162
raise_except(int excepts)163 LIBC_INLINE int raise_except(int excepts) {
164 float zero = 0.0f;
165 float one = 1.0f;
166 float large_value = FPBits<float>::max_normal().get_val();
167 float small_value = FPBits<float>::min_normal().get_val();
168 auto divfunc = [](float a, float b) {
169 __asm__ __volatile__("ldr s0, %0\n\t"
170 "ldr s1, %1\n\t"
171 "fdiv s0, s0, s1\n\t"
172 : // No outputs
173 : "m"(a), "m"(b)
174 : "s0", "s1" /* s0 and s1 are clobbered */);
175 };
176
177 uint32_t to_raise = FEnv::exception_value_from_status(excepts);
178 int result = 0;
179
180 if (to_raise & FEnv::EX_INVALID) {
181 divfunc(zero, zero);
182 uint32_t status_word = FEnv::get_status_word();
183 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_INVALID))
184 result = -1;
185 }
186
187 if (to_raise & FEnv::EX_DIVBYZERO) {
188 divfunc(one, zero);
189 uint32_t status_word = FEnv::get_status_word();
190 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_DIVBYZERO))
191 result = -1;
192 }
193 if (to_raise & FEnv::EX_OVERFLOW) {
194 divfunc(large_value, small_value);
195 uint32_t status_word = FEnv::get_status_word();
196 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_OVERFLOW))
197 result = -1;
198 }
199 if (to_raise & FEnv::EX_UNDERFLOW) {
200 divfunc(small_value, large_value);
201 uint32_t status_word = FEnv::get_status_word();
202 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_UNDERFLOW))
203 result = -1;
204 }
205 if (to_raise & FEnv::EX_INEXACT) {
206 float two = 2.0f;
207 float three = 3.0f;
208 // 2.0 / 3.0 cannot be represented exactly in any radix 2 floating point
209 // format.
210 divfunc(two, three);
211 uint32_t status_word = FEnv::get_status_word();
212 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_INEXACT))
213 result = -1;
214 }
215 if (to_raise & FEnv::EX_FLUSHTOZERO) {
216 // TODO: raise the flush to zero floating point exception.
217 result = -1;
218 }
219 return result;
220 }
221
get_round()222 LIBC_INLINE int get_round() {
223 uint32_t rounding_mode =
224 (FEnv::get_control_word() >> FEnv::ROUNDING_CONTROL_BIT_POSITION) & 0x3;
225 switch (rounding_mode) {
226 case FEnv::TONEAREST:
227 return FE_TONEAREST;
228 case FEnv::DOWNWARD:
229 return FE_DOWNWARD;
230 case FEnv::UPWARD:
231 return FE_UPWARD;
232 case FEnv::TOWARDZERO:
233 return FE_TOWARDZERO;
234 default:
235 return -1; // Error value.
236 }
237 }
238
set_round(int mode)239 LIBC_INLINE int set_round(int mode) {
240 uint16_t bit_value;
241 switch (mode) {
242 case FE_TONEAREST:
243 bit_value = FEnv::TONEAREST;
244 break;
245 case FE_DOWNWARD:
246 bit_value = FEnv::DOWNWARD;
247 break;
248 case FE_UPWARD:
249 bit_value = FEnv::UPWARD;
250 break;
251 case FE_TOWARDZERO:
252 bit_value = FEnv::TOWARDZERO;
253 break;
254 default:
255 return 1; // To indicate failure
256 }
257
258 uint32_t control_word = FEnv::get_control_word();
259 control_word &= ~(0x3 << FEnv::ROUNDING_CONTROL_BIT_POSITION);
260 control_word |= (bit_value << FEnv::ROUNDING_CONTROL_BIT_POSITION);
261 FEnv::set_control_word(control_word);
262
263 return 0;
264 }
265
get_env(fenv_t * envp)266 LIBC_INLINE int get_env(fenv_t *envp) {
267 FEnv::FPState *state = reinterpret_cast<FEnv::FPState *>(envp);
268 state->ControlWord = FEnv::get_control_word();
269 state->StatusWord = FEnv::get_status_word();
270 return 0;
271 }
272
set_env(const fenv_t * envp)273 LIBC_INLINE int set_env(const fenv_t *envp) {
274 if (envp == FE_DFL_ENV) {
275 // Default status and control words bits are all zeros so we just
276 // write zeros.
277 FEnv::set_status_word(0);
278 FEnv::set_control_word(0);
279 return 0;
280 }
281 const FEnv::FPState *state = reinterpret_cast<const FEnv::FPState *>(envp);
282 FEnv::set_control_word(static_cast<uint32_t>(state->ControlWord));
283 FEnv::set_status_word(static_cast<uint32_t>(state->StatusWord));
284 return 0;
285 }
286
287 } // namespace fputil
288 } // namespace LIBC_NAMESPACE_DECL
289
290 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_AARCH64_FENV_DARWIN_IMPL_H
291