diff options
Diffstat (limited to 'absl/random/internal/distribution_impl.h')
-rw-r--r-- | absl/random/internal/distribution_impl.h | 66 |
1 files changed, 0 insertions, 66 deletions
diff --git a/absl/random/internal/distribution_impl.h b/absl/random/internal/distribution_impl.h index 9b6ffb0f..49b3e1a6 100644 --- a/absl/random/internal/distribution_impl.h +++ b/absl/random/internal/distribution_impl.h @@ -188,72 +188,6 @@ struct RandU64ToReal<float> { } }; -inline uint128 MultiplyU64ToU128(uint64_t a, uint64_t b) { -#if defined(ABSL_HAVE_INTRINSIC_INT128) - return uint128(static_cast<__uint128_t>(a) * b); -#elif defined(ABSL_INTERNAL_USE_UMUL128) - // uint64_t * uint64_t => uint128 multiply using imul intrinsic on MSVC. - uint64_t high = 0; - const uint64_t low = _umul128(a, b, &high); - return absl::MakeUint128(high, low); -#else - // uint128(a) * uint128(b) in emulated mode computes a full 128-bit x 128-bit - // multiply. However there are many cases where that is not necessary, and it - // is only necessary to support a 64-bit x 64-bit = 128-bit multiply. This is - // for those cases. - const uint64_t a00 = static_cast<uint32_t>(a); - const uint64_t a32 = a >> 32; - const uint64_t b00 = static_cast<uint32_t>(b); - const uint64_t b32 = b >> 32; - - const uint64_t c00 = a00 * b00; - const uint64_t c32a = a00 * b32; - const uint64_t c32b = a32 * b00; - const uint64_t c64 = a32 * b32; - - const uint32_t carry = - static_cast<uint32_t>(((c00 >> 32) + static_cast<uint32_t>(c32a) + - static_cast<uint32_t>(c32b)) >> - 32); - - return absl::MakeUint128(c64 + (c32a >> 32) + (c32b >> 32) + carry, - c00 + (c32a << 32) + (c32b << 32)); -#endif -} - -// wide_multiply<T> multiplies two N-bit values to a 2N-bit result. -template <typename UIntType> -struct wide_multiply { - static constexpr size_t kN = std::numeric_limits<UIntType>::digits; - using input_type = UIntType; - using result_type = typename random_internal::unsigned_bits<kN * 2>::type; - - static result_type multiply(input_type a, input_type b) { - return static_cast<result_type>(a) * b; - } - - static input_type hi(result_type r) { return r >> kN; } - static input_type lo(result_type r) { return r; } - - static_assert(std::is_unsigned<UIntType>::value, - "Class-template wide_multiply<> argument must be unsigned."); -}; - -#ifndef ABSL_HAVE_INTRINSIC_INT128 -template <> -struct wide_multiply<uint64_t> { - using input_type = uint64_t; - using result_type = uint128; - - static result_type multiply(uint64_t a, uint64_t b) { - return MultiplyU64ToU128(a, b); - } - - static uint64_t hi(result_type r) { return Uint128High64(r); } - static uint64_t lo(result_type r) { return Uint128Low64(r); } -}; -#endif - } // namespace random_internal } // namespace absl |