libc/src/__support/FPUtil/aarch64/FEnvImpl.h

   1 //===-- 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_FENVIMPL_H
  10 #define LLVM_LIBC_SRC_SUPPORT_FPUTIL_AARCH64_FENVIMPL_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 <fenv.h>
  21 #include <stdint.h>
  22
  23 #include "src/__support/FPUtil/FPBits.h"
  24
  25 namespace __llvm_libc {
  26 namespace fputil {
  27
  28 struct FEnv {
  29   struct FPState {
  30     uint32_t ControlWord;
  31     uint32_t StatusWord;
  32   };
  33
  34   static_assert(
  35       sizeof(fenv_t) == sizeof(FPState),
  36       "Internal floating point state does not match the public fenv_t type.");
  37
  38   static constexpr uint32_t TONEAREST = 0x0;
  39   static constexpr uint32_t UPWARD = 0x1;
  40   static constexpr uint32_t DOWNWARD = 0x2;
  41   static constexpr uint32_t TOWARDZERO = 0x3;
  42
  43   static constexpr uint32_t INVALID = 0x1;
  44   static constexpr uint32_t DIVBYZERO = 0x2;
  45   static constexpr uint32_t OVERFLOW = 0x4;
  46   static constexpr uint32_t UNDERFLOW = 0x8;
  47   static constexpr uint32_t INEXACT = 0x10;
  48
  49   // Zero-th bit is the first bit.
  50   static constexpr uint32_t RoundingControlBitPosition = 22;
  51   static constexpr uint32_t ExceptionStatusFlagsBitPosition = 0;
  52   static constexpr uint32_t ExceptionControlFlagsBitPosition = 8;
  53
  54   LIBC_INLINE static uint32_t getStatusValueForExcept(int excepts) {
  55     return (excepts & FE_INVALID ? INVALID : 0) |
  56            (excepts & FE_DIVBYZERO ? DIVBYZERO : 0) |
  57            (excepts & FE_OVERFLOW ? OVERFLOW : 0) |
  58            (excepts & FE_UNDERFLOW ? UNDERFLOW : 0) |
  59            (excepts & FE_INEXACT ? INEXACT : 0);
  60   }
  61
  62   LIBC_INLINE static int exceptionStatusToMacro(uint32_t status) {
  63     return (status & INVALID ? FE_INVALID : 0) |
  64            (status & DIVBYZERO ? FE_DIVBYZERO : 0) |
  65            (status & OVERFLOW ? FE_OVERFLOW : 0) |
  66            (status & UNDERFLOW ? FE_UNDERFLOW : 0) |
  67            (status & INEXACT ? FE_INEXACT : 0);
  68   }
  69
  70   static uint32_t getControlWord() {
  71 #ifdef __clang__
  72     // GCC does not currently support __arm_rsr.
  73     return __arm_rsr("fpcr");
  74 #else
  75     return __builtin_aarch64_get_fpcr();
  76 #endif
  77   }
  78
  79   static void writeControlWord(uint32_t fpcr) {
  80 #ifdef __clang__
  81     // GCC does not currently support __arm_wsr.
  82     __arm_wsr("fpcr", fpcr);
  83 #else
  84     __builtin_aarch64_set_fpcr(fpcr);
  85 #endif
  86   }
  87
  88   static uint32_t getStatusWord() {
  89 #ifdef __clang__
  90     return __arm_rsr("fpsr");
  91 #else
  92     return __builtin_aarch64_get_fpsr();
  93 #endif
  94   }
  95
  96   static void writeStatusWord(uint32_t fpsr) {
  97 #ifdef __clang__
  98     __arm_wsr("fpsr", fpsr);
  99 #else
 100     __builtin_aarch64_set_fpsr(fpsr);
 101 #endif
 102   }
 103 };
 104
 105 LIBC_INLINE int enable_except(int excepts) {
 106   uint32_t newExcepts = FEnv::getStatusValueForExcept(excepts);
 107   uint32_t controlWord = FEnv::getControlWord();
 108   int oldExcepts =
 109       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
 110   controlWord |= (newExcepts << FEnv::ExceptionControlFlagsBitPosition);
 111   FEnv::writeControlWord(controlWord);
 112   return FEnv::exceptionStatusToMacro(oldExcepts);
 113 }
 114
 115 LIBC_INLINE int disable_except(int excepts) {
 116   uint32_t disabledExcepts = FEnv::getStatusValueForExcept(excepts);
 117   uint32_t controlWord = FEnv::getControlWord();
 118   int oldExcepts =
 119       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
 120   controlWord &= ~(disabledExcepts << FEnv::ExceptionControlFlagsBitPosition);
 121   FEnv::writeControlWord(controlWord);
 122   return FEnv::exceptionStatusToMacro(oldExcepts);
 123 }
 124
 125 LIBC_INLINE int get_except() {
 126   uint32_t controlWord = FEnv::getControlWord();
 127   int enabledExcepts =
 128       (controlWord >> FEnv::ExceptionControlFlagsBitPosition) & 0x1F;
 129   return FEnv::exceptionStatusToMacro(enabledExcepts);
 130 }
 131
 132 LIBC_INLINE int clear_except(int excepts) {
 133   uint32_t statusWord = FEnv::getStatusWord();
 134   uint32_t toClear = FEnv::getStatusValueForExcept(excepts);
 135   statusWord &= ~(toClear << FEnv::ExceptionStatusFlagsBitPosition);
 136   FEnv::writeStatusWord(statusWord);
 137   return 0;
 138 }
 139
 140 LIBC_INLINE int test_except(int excepts) {
 141   uint32_t toTest = FEnv::getStatusValueForExcept(excepts);
 142   uint32_t statusWord = FEnv::getStatusWord();
 143   return FEnv::exceptionStatusToMacro(
 144       (statusWord >> FEnv::ExceptionStatusFlagsBitPosition) & toTest);
 145 }
 146
 147 LIBC_INLINE int set_except(int excepts) {
 148   uint32_t statusWord = FEnv::getStatusWord();
 149   uint32_t statusValue = FEnv::getStatusValueForExcept(excepts);
 150   statusWord |= (statusValue << FEnv::ExceptionStatusFlagsBitPosition);
 151   FEnv::writeStatusWord(statusWord);
 152   return 0;
 153 }
 154
 155 LIBC_INLINE int raise_except(int excepts) {
 156   float zero = 0.0f;
 157   float one = 1.0f;
 158   float largeValue = float(FPBits<float>(FPBits<float>::MAX_NORMAL));
 159   float smallValue = float(FPBits<float>(FPBits<float>::MIN_NORMAL));
 160   auto divfunc = [](float a, float b) {
 161     __asm__ __volatile__("ldr  s0, %0\n\t"
 162                          "ldr  s1, %1\n\t"
 163                          "fdiv s0, s0, s1\n\t"
 164                          : // No outputs
 165                          : "m"(a), "m"(b)
 166                          : "s0", "s1" /* s0 and s1 are clobbered */);
 167   };
 168
 169   uint32_t toRaise = FEnv::getStatusValueForExcept(excepts);
 170   int result = 0;
 171
 172   if (toRaise & FEnv::INVALID) {
 173     divfunc(zero, zero);
 174     uint32_t statusWord = FEnv::getStatusWord();
 175     if (!((statusWord >> FEnv::ExceptionStatusFlagsBitPosition) &
 176           FEnv::INVALID))
 177       result = -1;
 178   }
 179
 180   if (toRaise & FEnv::DIVBYZERO) {
 181     divfunc(one, zero);
 182     uint32_t statusWord = FEnv::getStatusWord();
 183     if (!((statusWord >> FEnv::ExceptionStatusFlagsBitPosition) &
 184           FEnv::DIVBYZERO))
 185       result = -1;
 186   }
 187   if (toRaise & FEnv::OVERFLOW) {
 188     divfunc(largeValue, smallValue);
 189     uint32_t statusWord = FEnv::getStatusWord();
 190     if (!((statusWord >> FEnv::ExceptionStatusFlagsBitPosition) &
 191           FEnv::OVERFLOW))
 192       result = -1;
 193   }
 194   if (toRaise & FEnv::UNDERFLOW) {
 195     divfunc(smallValue, largeValue);
 196     uint32_t statusWord = FEnv::getStatusWord();
 197     if (!((statusWord >> FEnv::ExceptionStatusFlagsBitPosition) &
 198           FEnv::UNDERFLOW))
 199       result = -1;
 200   }
 201   if (toRaise & FEnv::INEXACT) {
 202     float two = 2.0f;
 203     float three = 3.0f;
 204     // 2.0 / 3.0 cannot be represented exactly in any radix 2 floating point
 205     // format.
 206     divfunc(two, three);
 207     uint32_t statusWord = FEnv::getStatusWord();
 208     if (!((statusWord >> FEnv::ExceptionStatusFlagsBitPosition) &
 209           FEnv::INEXACT))
 210       result = -1;
 211   }
 212   return result;
 213 }
 214
 215 LIBC_INLINE int get_round() {
 216   uint32_t roundingMode =
 217       (FEnv::getControlWord() >> FEnv::RoundingControlBitPosition) & 0x3;
 218   switch (roundingMode) {
 219   case FEnv::TONEAREST:
 220     return FE_TONEAREST;
 221   case FEnv::DOWNWARD:
 222     return FE_DOWNWARD;
 223   case FEnv::UPWARD:
 224     return FE_UPWARD;
 225   case FEnv::TOWARDZERO:
 226     return FE_TOWARDZERO;
 227   default:
 228     return -1; // Error value.
 229   }
 230 }
 231
 232 LIBC_INLINE int set_round(int mode) {
 233   uint16_t bitValue;
 234   switch (mode) {
 235   case FE_TONEAREST:
 236     bitValue = FEnv::TONEAREST;
 237     break;
 238   case FE_DOWNWARD:
 239     bitValue = FEnv::DOWNWARD;
 240     break;
 241   case FE_UPWARD:
 242     bitValue = FEnv::UPWARD;
 243     break;
 244   case FE_TOWARDZERO:
 245     bitValue = FEnv::TOWARDZERO;
 246     break;
 247   default:
 248     return 1; // To indicate failure
 249   }
 250
 251   uint32_t controlWord = FEnv::getControlWord();
 252   controlWord &= ~(0x3 << FEnv::RoundingControlBitPosition);
 253   controlWord |= (bitValue << FEnv::RoundingControlBitPosition);
 254   FEnv::writeControlWord(controlWord);
 255
 256   return 0;
 257 }
 258
 259 LIBC_INLINE int get_env(fenv_t *envp) {
 260   FEnv::FPState *state = reinterpret_cast<FEnv::FPState *>(envp);
 261   state->ControlWord = FEnv::getControlWord();
 262   state->StatusWord = FEnv::getStatusWord();
 263   return 0;
 264 }
 265
 266 LIBC_INLINE int set_env(const fenv_t *envp) {
 267   if (envp == FE_DFL_ENV) {
 268     // Default status and control words bits are all zeros so we just
 269     // write zeros.
 270     FEnv::writeStatusWord(0);
 271     FEnv::writeControlWord(0);
 272     return 0;
 273   }
 274   const FEnv::FPState *state = reinterpret_cast<const FEnv::FPState *>(envp);
 275   FEnv::writeControlWord(state->ControlWord);
 276   FEnv::writeStatusWord(state->StatusWord);
 277   return 0;
 278 }
 279
 280 } // namespace fputil
 281 } // namespace __llvm_libc
 282
 283 #endif // LLVM_LIBC_SRC_SUPPORT_FPUTIL_AARCH64_FENVIMPL_H