libc/src/__support/FPUtil/generic/mul.h

   1 //===-- Multiplication of IEEE 754 floating-point numbers -------*- 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_GENERIC_MUL_H
  10 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_MUL_H
  11
  12 #include "hdr/errno_macros.h"
  13 #include "hdr/fenv_macros.h"
  14 #include "src/__support/CPP/bit.h"
  15 #include "src/__support/CPP/type_traits.h"
  16 #include "src/__support/FPUtil/BasicOperations.h"
  17 #include "src/__support/FPUtil/FEnvImpl.h"
  18 #include "src/__support/FPUtil/FPBits.h"
  19 #include "src/__support/FPUtil/dyadic_float.h"
  20 #include "src/__support/macros/attributes.h"
  21 #include "src/__support/macros/config.h"
  22 #include "src/__support/macros/optimization.h"
  23
  24 namespace LIBC_NAMESPACE_DECL {
  25 namespace fputil::generic {
  26
  27 template <typename OutType, typename InType>
  28 LIBC_INLINE cpp::enable_if_t<cpp::is_floating_point_v<OutType> &&
  29                                  cpp::is_floating_point_v<InType> &&
  30                                  sizeof(OutType) <= sizeof(InType),
  31                              OutType>
  32 mul(InType x, InType y) {
  33   using OutFPBits = FPBits<OutType>;
  34   using OutStorageType = typename OutFPBits::StorageType;
  35   using InFPBits = FPBits<InType>;
  36   using InStorageType = typename InFPBits::StorageType;
  37   // The product of two p-digit numbers is a 2p-digit number.
  38   using DyadicFloat =
  39       DyadicFloat<cpp::bit_ceil(2 * static_cast<size_t>(InFPBits::SIG_LEN))>;
  40
  41   InFPBits x_bits(x);
  42   InFPBits y_bits(y);
  43
  44   Sign result_sign = x_bits.sign() == y_bits.sign() ? Sign::POS : Sign::NEG;
  45
  46   if (LIBC_UNLIKELY(x_bits.is_inf_or_nan() || y_bits.is_inf_or_nan() ||
  47                     x_bits.is_zero() || y_bits.is_zero())) {
  48     if (x_bits.is_nan() || y_bits.is_nan()) {
  49       if (x_bits.is_signaling_nan() || y_bits.is_signaling_nan())
  50         raise_except_if_required(FE_INVALID);
  51
  52       if (x_bits.is_quiet_nan()) {
  53         InStorageType x_payload = x_bits.get_mantissa();
  54         x_payload >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
  55         return OutFPBits::quiet_nan(x_bits.sign(),
  56                                     static_cast<OutStorageType>(x_payload))
  57             .get_val();
  58       }
  59
  60       if (y_bits.is_quiet_nan()) {
  61         InStorageType y_payload = y_bits.get_mantissa();
  62         y_payload >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
  63         return OutFPBits::quiet_nan(y_bits.sign(),
  64                                     static_cast<OutStorageType>(y_payload))
  65             .get_val();
  66       }
  67
  68       return OutFPBits::quiet_nan().get_val();
  69     }
  70
  71     if (x_bits.is_inf()) {
  72       if (y_bits.is_zero()) {
  73         set_errno_if_required(EDOM);
  74         raise_except_if_required(FE_INVALID);
  75         return OutFPBits::quiet_nan().get_val();
  76       }
  77
  78       return OutFPBits::inf(result_sign).get_val();
  79     }
  80
  81     if (y_bits.is_inf()) {
  82       if (x_bits.is_zero()) {
  83         set_errno_if_required(EDOM);
  84         raise_except_if_required(FE_INVALID);
  85         return OutFPBits::quiet_nan().get_val();
  86       }
  87
  88       return OutFPBits::inf(result_sign).get_val();
  89     }
  90
  91     // Now either x or y is zero, and the other one is finite.
  92     return OutFPBits::zero(result_sign).get_val();
  93   }
  94
  95   DyadicFloat xd(x);
  96   DyadicFloat yd(y);
  97
  98   DyadicFloat result = quick_mul(xd, yd);
  99   return result.template as<OutType, /*ShouldSignalExceptions=*/true>();
 100 }
 101
 102 } // namespace fputil::generic
 103 } // namespace LIBC_NAMESPACE_DECL
 104
 105 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_MUL_H