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/properties/architectures.h"
14
15 #if !defined(LIBC_TARGET_ARCH_IS_AARCH64) || !defined(__APPLE__)
16 #error "Invalid include"
17 #endif
18
19 #include <arm_acle.h>
20 #include <stdint.h>
21
22 #include "hdr/fenv_macros.h"
23 #include "hdr/types/fenv_t.h"
24 #include "src/__support/FPUtil/FPBits.h"
25
26 namespace LIBC_NAMESPACE {
27 namespace fputil {
28
29 struct FEnv {
30 struct FPState {
31 uint64_t StatusWord;
32 uint64_t ControlWord;
33 };
34
35 static_assert(
36 sizeof(fenv_t) == sizeof(FPState),
37 "Internal floating point state does not match the public fenv_t type.");
38
39 static constexpr uint32_t TONEAREST = 0x0;
40 static constexpr uint32_t UPWARD = 0x1;
41 static constexpr uint32_t DOWNWARD = 0x2;
42 static constexpr uint32_t TOWARDZERO = 0x3;
43
44 // These will be the exception flags we use for exception values normalized
45 // from both status word and control word.
46 // We add EX_ prefix to the names since macOS <math.h> defines OVERFLOW and
47 // UNDERFLOW macros.
48 static constexpr uint32_t EX_INVALID = 0x1;
49 static constexpr uint32_t EX_DIVBYZERO = 0x2;
50 static constexpr uint32_t EX_OVERFLOW = 0x4;
51 static constexpr uint32_t EX_UNDERFLOW = 0x8;
52 static constexpr uint32_t EX_INEXACT = 0x10;
53 // __APPLE__ ARM64 has an extra flag that is raised when a denormal is flushed
54 // to zero.
55 static constexpr uint32_t EX_FLUSHTOZERO = 0x20;
56
57 // Zero-th bit is the first bit.
58 static constexpr uint32_t ROUNDING_CONTROL_BIT_POSITION = 22;
59
60 // In addition to the 5 floating point exceptions, macOS on arm64 defines
61 // another floating point exception: FE_FLUSHTOZERO, which is controlled by
62 // __fpcr_flush_to_zero bit in the FPCR register. This control bit is
63 // located in a different place from FE_FLUSHTOZERO status bit relative to
64 // the other exceptions.
exception_value_from_statusFEnv65 LIBC_INLINE static uint32_t exception_value_from_status(int status) {
66 return ((status & FE_INVALID) ? EX_INVALID : 0) |
67 ((status & FE_DIVBYZERO) ? EX_DIVBYZERO : 0) |
68 ((status & FE_OVERFLOW) ? EX_OVERFLOW : 0) |
69 ((status & FE_UNDERFLOW) ? EX_UNDERFLOW : 0) |
70 ((status & FE_INEXACT) ? EX_INEXACT : 0) |
71 ((status & FE_FLUSHTOZERO) ? EX_FLUSHTOZERO : 0);
72 }
73
exception_value_from_controlFEnv74 LIBC_INLINE static uint32_t exception_value_from_control(int control) {
75 return ((control & __fpcr_trap_invalid) ? EX_INVALID : 0) |
76 ((control & __fpcr_trap_divbyzero) ? EX_DIVBYZERO : 0) |
77 ((control & __fpcr_trap_overflow) ? EX_OVERFLOW : 0) |
78 ((control & __fpcr_trap_underflow) ? EX_UNDERFLOW : 0) |
79 ((control & __fpcr_trap_inexact) ? EX_INEXACT : 0) |
80 ((control & __fpcr_flush_to_zero) ? EX_FLUSHTOZERO : 0);
81 }
82
exception_value_to_statusFEnv83 LIBC_INLINE static int exception_value_to_status(uint32_t excepts) {
84 return ((excepts & EX_INVALID) ? FE_INVALID : 0) |
85 ((excepts & EX_DIVBYZERO) ? FE_DIVBYZERO : 0) |
86 ((excepts & EX_OVERFLOW) ? FE_OVERFLOW : 0) |
87 ((excepts & EX_UNDERFLOW) ? FE_UNDERFLOW : 0) |
88 ((excepts & EX_INEXACT) ? FE_INEXACT : 0) |
89 ((excepts & EX_FLUSHTOZERO) ? FE_FLUSHTOZERO : 0);
90 }
91
exception_value_to_controlFEnv92 LIBC_INLINE static int exception_value_to_control(uint32_t excepts) {
93 return ((excepts & EX_INVALID) ? __fpcr_trap_invalid : 0) |
94 ((excepts & EX_DIVBYZERO) ? __fpcr_trap_divbyzero : 0) |
95 ((excepts & EX_OVERFLOW) ? __fpcr_trap_overflow : 0) |
96 ((excepts & EX_UNDERFLOW) ? __fpcr_trap_underflow : 0) |
97 ((excepts & EX_INEXACT) ? __fpcr_trap_inexact : 0) |
98 ((excepts & EX_FLUSHTOZERO) ? __fpcr_flush_to_zero : 0);
99 }
100
get_control_wordFEnv101 LIBC_INLINE static uint32_t get_control_word() { return __arm_rsr("fpcr"); }
102
set_control_wordFEnv103 LIBC_INLINE static void set_control_word(uint32_t fpcr) {
104 __arm_wsr("fpcr", fpcr);
105 }
106
get_status_wordFEnv107 LIBC_INLINE static uint32_t get_status_word() { return __arm_rsr("fpsr"); }
108
set_status_wordFEnv109 LIBC_INLINE static void set_status_word(uint32_t fpsr) {
110 __arm_wsr("fpsr", fpsr);
111 }
112 };
113
enable_except(int excepts)114 LIBC_INLINE int enable_except(int excepts) {
115 uint32_t new_excepts = FEnv::exception_value_from_status(excepts);
116 uint32_t control_word = FEnv::get_control_word();
117 uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
118 if (new_excepts != old_excepts) {
119 control_word |= FEnv::exception_value_to_control(new_excepts);
120 FEnv::set_control_word(control_word);
121 }
122 return FEnv::exception_value_to_status(old_excepts);
123 }
124
disable_except(int excepts)125 LIBC_INLINE int disable_except(int excepts) {
126 uint32_t disabled_excepts = FEnv::exception_value_from_status(excepts);
127 uint32_t control_word = FEnv::get_control_word();
128 uint32_t old_excepts = FEnv::exception_value_from_control(control_word);
129 control_word &= ~FEnv::exception_value_to_control(disabled_excepts);
130 FEnv::set_control_word(control_word);
131 return FEnv::exception_value_to_status(old_excepts);
132 }
133
get_except()134 LIBC_INLINE int get_except() {
135 uint32_t control_word = FEnv::get_control_word();
136 uint32_t enabled_excepts = FEnv::exception_value_from_control(control_word);
137 return FEnv::exception_value_to_status(enabled_excepts);
138 }
139
clear_except(int excepts)140 LIBC_INLINE int clear_except(int excepts) {
141 uint32_t status_word = FEnv::get_status_word();
142 uint32_t except_value = FEnv::exception_value_from_status(excepts);
143 status_word &= ~FEnv::exception_value_to_status(except_value);
144 FEnv::set_status_word(status_word);
145 return 0;
146 }
147
test_except(int excepts)148 LIBC_INLINE int test_except(int excepts) {
149 uint32_t statusWord = FEnv::get_status_word();
150 uint32_t ex_value = FEnv::exception_value_from_status(excepts);
151 return statusWord & FEnv::exception_value_to_status(ex_value);
152 }
153
set_except(int excepts)154 LIBC_INLINE int set_except(int excepts) {
155 uint32_t status_word = FEnv::get_status_word();
156 uint32_t new_exceptions = FEnv::exception_value_from_status(excepts);
157 status_word |= FEnv::exception_value_to_status(new_exceptions);
158 FEnv::set_status_word(status_word);
159 return 0;
160 }
161
raise_except(int excepts)162 LIBC_INLINE int raise_except(int excepts) {
163 float zero = 0.0f;
164 float one = 1.0f;
165 float large_value = FPBits<float>::max_normal().get_val();
166 float small_value = FPBits<float>::min_normal().get_val();
167 auto divfunc = [](float a, float b) {
168 __asm__ __volatile__("ldr s0, %0\n\t"
169 "ldr s1, %1\n\t"
170 "fdiv s0, s0, s1\n\t"
171 : // No outputs
172 : "m"(a), "m"(b)
173 : "s0", "s1" /* s0 and s1 are clobbered */);
174 };
175
176 uint32_t to_raise = FEnv::exception_value_from_status(excepts);
177 int result = 0;
178
179 if (to_raise & FEnv::EX_INVALID) {
180 divfunc(zero, zero);
181 uint32_t status_word = FEnv::get_status_word();
182 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_INVALID))
183 result = -1;
184 }
185
186 if (to_raise & FEnv::EX_DIVBYZERO) {
187 divfunc(one, zero);
188 uint32_t status_word = FEnv::get_status_word();
189 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_DIVBYZERO))
190 result = -1;
191 }
192 if (to_raise & FEnv::EX_OVERFLOW) {
193 divfunc(large_value, small_value);
194 uint32_t status_word = FEnv::get_status_word();
195 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_OVERFLOW))
196 result = -1;
197 }
198 if (to_raise & FEnv::EX_UNDERFLOW) {
199 divfunc(small_value, large_value);
200 uint32_t status_word = FEnv::get_status_word();
201 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_UNDERFLOW))
202 result = -1;
203 }
204 if (to_raise & FEnv::EX_INEXACT) {
205 float two = 2.0f;
206 float three = 3.0f;
207 // 2.0 / 3.0 cannot be represented exactly in any radix 2 floating point
208 // format.
209 divfunc(two, three);
210 uint32_t status_word = FEnv::get_status_word();
211 if (!(FEnv::exception_value_from_status(status_word) & FEnv::EX_INEXACT))
212 result = -1;
213 }
214 if (to_raise & FEnv::EX_FLUSHTOZERO) {
215 // TODO: raise the flush to zero floating point exception.
216 result = -1;
217 }
218 return result;
219 }
220
get_round()221 LIBC_INLINE int get_round() {
222 uint32_t rounding_mode =
223 (FEnv::get_control_word() >> FEnv::ROUNDING_CONTROL_BIT_POSITION) & 0x3;
224 switch (rounding_mode) {
225 case FEnv::TONEAREST:
226 return FE_TONEAREST;
227 case FEnv::DOWNWARD:
228 return FE_DOWNWARD;
229 case FEnv::UPWARD:
230 return FE_UPWARD;
231 case FEnv::TOWARDZERO:
232 return FE_TOWARDZERO;
233 default:
234 return -1; // Error value.
235 }
236 }
237
set_round(int mode)238 LIBC_INLINE int set_round(int mode) {
239 uint16_t bit_value;
240 switch (mode) {
241 case FE_TONEAREST:
242 bit_value = FEnv::TONEAREST;
243 break;
244 case FE_DOWNWARD:
245 bit_value = FEnv::DOWNWARD;
246 break;
247 case FE_UPWARD:
248 bit_value = FEnv::UPWARD;
249 break;
250 case FE_TOWARDZERO:
251 bit_value = FEnv::TOWARDZERO;
252 break;
253 default:
254 return 1; // To indicate failure
255 }
256
257 uint32_t control_word = FEnv::get_control_word();
258 control_word &= ~(0x3 << FEnv::ROUNDING_CONTROL_BIT_POSITION);
259 control_word |= (bit_value << FEnv::ROUNDING_CONTROL_BIT_POSITION);
260 FEnv::set_control_word(control_word);
261
262 return 0;
263 }
264
get_env(fenv_t * envp)265 LIBC_INLINE int get_env(fenv_t *envp) {
266 FEnv::FPState *state = reinterpret_cast<FEnv::FPState *>(envp);
267 state->ControlWord = FEnv::get_control_word();
268 state->StatusWord = FEnv::get_status_word();
269 return 0;
270 }
271
set_env(const fenv_t * envp)272 LIBC_INLINE int set_env(const fenv_t *envp) {
273 if (envp == FE_DFL_ENV) {
274 // Default status and control words bits are all zeros so we just
275 // write zeros.
276 FEnv::set_status_word(0);
277 FEnv::set_control_word(0);
278 return 0;
279 }
280 const FEnv::FPState *state = reinterpret_cast<const FEnv::FPState *>(envp);
281 FEnv::set_control_word(static_cast<uint32_t>(state->ControlWord));
282 FEnv::set_status_word(static_cast<uint32_t>(state->StatusWord));
283 return 0;
284 }
285
286 } // namespace fputil
287 } // namespace LIBC_NAMESPACE
288
289 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_AARCH64_FENV_DARWIN_IMPL_H
290