libc/src/__support/integer_utils.h

   1 //===-- Utilities for integers. ---------------------------------*- 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_INTEGER_UTILS_H
  10 #define LLVM_LIBC_SRC_SUPPORT_INTEGER_UTILS_H
  11
  12 #include "src/__support/CPP/type_traits.h"
  13 #include "src/__support/common.h"
  14
  15 #include "builtin_wrappers.h"
  16 #include "number_pair.h"
  17
  18 #include <stdint.h>
  19
  20 namespace __llvm_libc {
  21
  22 template <typename T> NumberPair<T> full_mul(T a, T b);
  23
  24 template <>
  25 LIBC_INLINE NumberPair<uint32_t> full_mul<uint32_t>(uint32_t a, uint32_t b) {
  26   uint64_t prod = uint64_t(a) * uint64_t(b);
  27   NumberPair<uint32_t> result;
  28   result.lo = uint32_t(prod);
  29   result.hi = uint32_t(prod >> 32);
  30   return result;
  31 }
  32
  33 template <>
  34 LIBC_INLINE NumberPair<uint64_t> full_mul<uint64_t>(uint64_t a, uint64_t b) {
  35 #ifdef __SIZEOF_INT128__
  36   __uint128_t prod = __uint128_t(a) * __uint128_t(b);
  37   NumberPair<uint64_t> result;
  38   result.lo = uint64_t(prod);
  39   result.hi = uint64_t(prod >> 64);
  40   return result;
  41 #else
  42   NumberPair<uint64_t> pa = split(a);
  43   NumberPair<uint64_t> pb = split(b);
  44   NumberPair<uint64_t> prod;
  45
  46   prod.lo = pa.lo * pb.lo;                           // exact
  47   prod.hi = pa.hi * pb.hi;                           // exact
  48   NumberPair<uint64_t> lo_hi = split(pa.lo * pb.hi); // exact
  49   NumberPair<uint64_t> hi_lo = split(pa.hi * pb.lo); // exact
  50
  51   auto r1 = add_with_carry(prod.lo, lo_hi.lo << 32, uint64_t(0));
  52   prod.lo = r1.sum;
  53   prod.hi = add_with_carry(prod.hi, lo_hi.hi, r1.carry).sum;
  54
  55   auto r2 = add_with_carry(prod.lo, hi_lo.lo << 32, uint64_t(0));
  56   prod.lo = r2.sum;
  57   prod.hi = add_with_carry(prod.hi, hi_lo.hi, r2.carry).sum;
  58
  59   return prod;
  60 #endif // __SIZEOF_INT128__
  61 }
  62
  63 } // namespace __llvm_libc
  64
  65 #endif // LLVM_LIBC_SRC_SUPPORT_INTEGER_UTILS_H