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(uint32_t 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(uint32_t 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 uint32_t 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 uint32_t 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 =
117 FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
118 uint32_t control_word = FEnv::get_control_word();
119 uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
120 if (new_excepts != old_excepts) {
121 control_word |= FEnv::exception_value_to_control(new_excepts);
122 FEnv::set_control_word(control_word);
123 }
124 return static_cast<int>(FEnv::exception_value_to_status(old_excepts));
125 }
126
disable_except(int excepts)127 LIBC_INLINE int disable_except(int excepts) {
128 uint32_t disabled_excepts =
129 FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
130 uint32_t control_word = FEnv::get_control_word();
131 uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
132 control_word &= ~FEnv::exception_value_to_control(disabled_excepts);
133 FEnv::set_control_word(control_word);
134 return static_cast<int>(FEnv::exception_value_to_status(old_excepts));
135 }
136
get_except()137 LIBC_INLINE int get_except() {
138 uint32_t control_word = FEnv::get_control_word();
139 uint32_t enabled_excepts = FEnv::exception_value_from_control(control_word);
140 return static_cast<int>(FEnv::exception_value_to_status(enabled_excepts));
141 }
142
clear_except(int excepts)143 LIBC_INLINE int clear_except(int excepts) {
144 uint32_t status_word = FEnv::get_status_word();
145 uint32_t except_value =
146 FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
147 status_word &= ~FEnv::exception_value_to_status(except_value);
148 FEnv::set_status_word(status_word);
149 return 0;
150 }
151
test_except(int excepts)152 LIBC_INLINE int test_except(int excepts) {
153 uint32_t statusWord = FEnv::get_status_word();
154 uint32_t ex_value =
155 FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
156 return static_cast<int>(statusWord &
157 FEnv::exception_value_to_status(ex_value));
158 }
159
set_except(int excepts)160 LIBC_INLINE int set_except(int excepts) {
161 uint32_t status_word = FEnv::get_status_word();
162 uint32_t new_exceptions =
163 FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
164 status_word |= FEnv::exception_value_to_status(new_exceptions);
165 FEnv::set_status_word(status_word);
166 return 0;
167 }
168
raise_except(int excepts)169 LIBC_INLINE int raise_except(int excepts) {
170 float zero = 0.0f;
171 float one = 1.0f;
172 float large_value = FPBits<float>::max_normal().get_val();
173 float small_value = FPBits<float>::min_normal().get_val();
174 auto divfunc = [](float a, float b) {
175 __asm__ __volatile__("ldr s0, %0\n\t"
176 "ldr s1, %1\n\t"
177 "fdiv s0, s0, s1\n\t"
178 : // No outputs
179 : "m"(a), "m"(b)
180 : "s0", "s1" /* s0 and s1 are clobbered */);
181 };
182
183 uint32_t to_raise =
184 FEnv::exception_value_from_status(static_cast<uint32_t>(excepts));
185 int result = 0;
186
187 if (to_raise & FEnv::EX_INVALID) {
188 divfunc(zero, zero);
189 uint32_t status_word = FEnv::get_status_word();
190 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_INVALID))
191 result = -1;
192 }
193
194 if (to_raise & FEnv::EX_DIVBYZERO) {
195 divfunc(one, zero);
196 uint32_t status_word = FEnv::get_status_word();
197 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_DIVBYZERO))
198 result = -1;
199 }
200 if (to_raise & FEnv::EX_OVERFLOW) {
201 divfunc(large_value, small_value);
202 uint32_t status_word = FEnv::get_status_word();
203 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_OVERFLOW))
204 result = -1;
205 }
206 if (to_raise & FEnv::EX_UNDERFLOW) {
207 divfunc(small_value, large_value);
208 uint32_t status_word = FEnv::get_status_word();
209 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_UNDERFLOW))
210 result = -1;
211 }
212 if (to_raise & FEnv::EX_INEXACT) {
213 float two = 2.0f;
214 float three = 3.0f;
215 // 2.0 / 3.0 cannot be represented exactly in any radix 2 floating point
216 // format.
217 divfunc(two, three);
218 uint32_t status_word = FEnv::get_status_word();
219 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_INEXACT))
220 result = -1;
221 }
222 if (to_raise & FEnv::EX_FLUSHTOZERO) {
223 // TODO: raise the flush to zero floating point exception.
224 result = -1;
225 }
226 return result;
227 }
228
get_round()229 LIBC_INLINE int get_round() {
230 uint32_t rounding_mode =
231 (FEnv::get_control_word() >> FEnv::ROUNDING_CONTROL_BIT_POSITION) & 0x3;
232 switch (rounding_mode) {
233 case FEnv::TONEAREST:
234 return FE_TONEAREST;
235 case FEnv::DOWNWARD:
236 return FE_DOWNWARD;
237 case FEnv::UPWARD:
238 return FE_UPWARD;
239 case FEnv::TOWARDZERO:
240 return FE_TOWARDZERO;
241 default:
242 return -1; // Error value.
243 }
244 }
245
set_round(int mode)246 LIBC_INLINE int set_round(int mode) {
247 uint32_t bit_value;
248 switch (mode) {
249 case FE_TONEAREST:
250 bit_value = FEnv::TONEAREST;
251 break;
252 case FE_DOWNWARD:
253 bit_value = FEnv::DOWNWARD;
254 break;
255 case FE_UPWARD:
256 bit_value = FEnv::UPWARD;
257 break;
258 case FE_TOWARDZERO:
259 bit_value = FEnv::TOWARDZERO;
260 break;
261 default:
262 return 1; // To indicate failure
263 }
264
265 uint32_t control_word = FEnv::get_control_word();
266 control_word &= ~(0x3u << FEnv::ROUNDING_CONTROL_BIT_POSITION);
267 control_word |= (bit_value << FEnv::ROUNDING_CONTROL_BIT_POSITION);
268 FEnv::set_control_word(control_word);
269
270 return 0;
271 }
272
get_env(fenv_t * envp)273 LIBC_INLINE int get_env(fenv_t *envp) {
274 FEnv::FPState *state = reinterpret_cast<FEnv::FPState *>(envp);
275 state->ControlWord = FEnv::get_control_word();
276 state->StatusWord = FEnv::get_status_word();
277 return 0;
278 }
279
set_env(const fenv_t * envp)280 LIBC_INLINE int set_env(const fenv_t *envp) {
281 if (envp == FE_DFL_ENV) {
282 // Default status and control words bits are all zeros so we just
283 // write zeros.
284 FEnv::set_status_word(0);
285 FEnv::set_control_word(0);
286 return 0;
287 }
288 const FEnv::FPState *state = reinterpret_cast<const FEnv::FPState *>(envp);
289 FEnv::set_control_word(static_cast<uint32_t>(state->ControlWord));
290 FEnv::set_status_word(static_cast<uint32_t>(state->StatusWord));
291 return 0;
292 }
293
294 } // namespace fputil
295 } // namespace LIBC_NAMESPACE_DECL
296
297 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_AARCH64_FENV_DARWIN_IMPL_H
298