-- d35c72d705155dcd89a92835103540f14c643d10 by Gennadiy Rozental <rogeeff@google.com>: helpxml changed to report types of flags with built-in value type. PiperOrigin-RevId: 275131440 -- f3478792943d7dd40a6ef6083a8e5d374f43a65e by Abseil Team <absl-team@google.com>: Add space padding tests for hex conversions. PiperOrigin-RevId: 275120155 -- 7c2e4725403e173660f33f94af686a75d3722936 by Andy Soffer <asoffer@google.com>: Fix https://github.com/abseil/abseil-cpp/issues/379 by renaming `roundup` to `round_up` PiperOrigin-RevId: 275106110 -- 84cb30d6ee509961ac4359cfdda1360973b9527d by Laramie Leavitt <lar@google.com>: Move random_internal::wide_multiply into a file by the same name. PiperOrigin-RevId: 275059359 -- 06d691a8c187b5d899e7863784b23bdcfd580cb2 by Abseil Team <absl-team@google.com>: Add missing "return" keyword. PiperOrigin-RevId: 275036408 GitOrigin-RevId: d35c72d705155dcd89a92835103540f14c643d10 Change-Id: Id837b4de6c9cfe18f0a088363754bfe389df985bpull/393/head
Abseil Team
5 years ago
committed by
Andy Soffer
parent
ab3552a189
commit
a15364ce4d
12 changed files with 275 additions and 118 deletions
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// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_RANDOM_INTERNAL_WIDE_MULTIPLY_H_ |
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#define ABSL_RANDOM_INTERNAL_WIDE_MULTIPLY_H_ |
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#include <cstdint> |
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#include <limits> |
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#include <type_traits> |
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#if (defined(_WIN32) || defined(_WIN64)) && defined(_M_IA64) |
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#include <intrin.h> // NOLINT(build/include_order) |
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#pragma intrinsic(_umul128) |
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#define ABSL_INTERNAL_USE_UMUL128 1 |
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#endif |
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#include "absl/base/config.h" |
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#include "absl/base/internal/bits.h" |
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#include "absl/numeric/int128.h" |
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#include "absl/random/internal/traits.h" |
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namespace absl { |
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namespace random_internal { |
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// Helper object to multiply two 64-bit values to a 128-bit value.
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// MultiplyU64ToU128 multiplies two 64-bit values to a 128-bit value.
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// If an intrinsic is available, it is used, otherwise use native 32-bit
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// multiplies to construct the result.
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inline uint128 MultiplyU64ToU128(uint64_t a, uint64_t b) { |
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#if defined(ABSL_HAVE_INTRINSIC_INT128) |
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return uint128(static_cast<__uint128_t>(a) * b); |
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#elif defined(ABSL_INTERNAL_USE_UMUL128) |
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// uint64_t * uint64_t => uint128 multiply using imul intrinsic on MSVC.
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uint64_t high = 0; |
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const uint64_t low = _umul128(a, b, &high); |
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return absl::MakeUint128(high, low); |
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#else |
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// uint128(a) * uint128(b) in emulated mode computes a full 128-bit x 128-bit
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// multiply. However there are many cases where that is not necessary, and it
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// is only necessary to support a 64-bit x 64-bit = 128-bit multiply. This is
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// for those cases.
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const uint64_t a00 = static_cast<uint32_t>(a); |
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const uint64_t a32 = a >> 32; |
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const uint64_t b00 = static_cast<uint32_t>(b); |
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const uint64_t b32 = b >> 32; |
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const uint64_t c00 = a00 * b00; |
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const uint64_t c32a = a00 * b32; |
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const uint64_t c32b = a32 * b00; |
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const uint64_t c64 = a32 * b32; |
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const uint32_t carry = |
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static_cast<uint32_t>(((c00 >> 32) + static_cast<uint32_t>(c32a) + |
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static_cast<uint32_t>(c32b)) >> |
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32); |
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return absl::MakeUint128(c64 + (c32a >> 32) + (c32b >> 32) + carry, |
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c00 + (c32a << 32) + (c32b << 32)); |
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#endif |
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} |
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// wide_multiply<T> multiplies two N-bit values to a 2N-bit result.
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template <typename UIntType> |
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struct wide_multiply { |
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static constexpr size_t kN = std::numeric_limits<UIntType>::digits; |
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using input_type = UIntType; |
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using result_type = typename random_internal::unsigned_bits<kN * 2>::type; |
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static result_type multiply(input_type a, input_type b) { |
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return static_cast<result_type>(a) * b; |
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} |
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static input_type hi(result_type r) { return r >> kN; } |
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static input_type lo(result_type r) { return r; } |
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static_assert(std::is_unsigned<UIntType>::value, |
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"Class-template wide_multiply<> argument must be unsigned."); |
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}; |
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#ifndef ABSL_HAVE_INTRINSIC_INT128 |
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template <> |
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struct wide_multiply<uint64_t> { |
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using input_type = uint64_t; |
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using result_type = uint128; |
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static result_type multiply(uint64_t a, uint64_t b) { |
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return MultiplyU64ToU128(a, b); |
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} |
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static uint64_t hi(result_type r) { return Uint128High64(r); } |
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static uint64_t lo(result_type r) { return Uint128Low64(r); } |
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}; |
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#endif |
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} // namespace random_internal
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} // namespace absl
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#endif // ABSL_RANDOM_INTERNAL_WIDE_MULTIPLY_H_
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@ -0,0 +1,66 @@ |
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// Copyright 2017 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/random/internal/wide_multiply.h" |
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#include "gtest/gtest.h" |
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#include "absl/base/internal/bits.h" |
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#include "absl/numeric/int128.h" |
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using absl::random_internal::MultiplyU64ToU128; |
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namespace { |
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TEST(WideMultiplyTest, MultiplyU64ToU128Test) { |
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constexpr uint64_t k1 = 1; |
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constexpr uint64_t kMax = ~static_cast<uint64_t>(0); |
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EXPECT_EQ(absl::uint128(0), MultiplyU64ToU128(0, 0)); |
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// Max uint64
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EXPECT_EQ(MultiplyU64ToU128(kMax, kMax), |
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absl::MakeUint128(0xfffffffffffffffe, 0x0000000000000001)); |
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EXPECT_EQ(absl::MakeUint128(0, kMax), MultiplyU64ToU128(kMax, 1)); |
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EXPECT_EQ(absl::MakeUint128(0, kMax), MultiplyU64ToU128(1, kMax)); |
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for (int i = 0; i < 64; ++i) { |
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EXPECT_EQ(absl::MakeUint128(0, kMax) << i, |
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MultiplyU64ToU128(kMax, k1 << i)); |
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EXPECT_EQ(absl::MakeUint128(0, kMax) << i, |
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MultiplyU64ToU128(k1 << i, kMax)); |
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} |
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// 1-bit x 1-bit.
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for (int i = 0; i < 64; ++i) { |
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for (int j = 0; j < 64; ++j) { |
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EXPECT_EQ(absl::MakeUint128(0, 1) << (i + j), |
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MultiplyU64ToU128(k1 << i, k1 << j)); |
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EXPECT_EQ(absl::MakeUint128(0, 1) << (i + j), |
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MultiplyU64ToU128(k1 << i, k1 << j)); |
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} |
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} |
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// Verified multiplies
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EXPECT_EQ(MultiplyU64ToU128(0xffffeeeeddddcccc, 0xbbbbaaaa99998888), |
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absl::MakeUint128(0xbbbb9e2692c5dddc, 0xc28f7531048d2c60)); |
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EXPECT_EQ(MultiplyU64ToU128(0x0123456789abcdef, 0xfedcba9876543210), |
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absl::MakeUint128(0x0121fa00ad77d742, 0x2236d88fe5618cf0)); |
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EXPECT_EQ(MultiplyU64ToU128(0x0123456789abcdef, 0xfdb97531eca86420), |
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absl::MakeUint128(0x0120ae99d26725fc, 0xce197f0ecac319e0)); |
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EXPECT_EQ(MultiplyU64ToU128(0x97a87f4f261ba3f2, 0xfedcba9876543210), |
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absl::MakeUint128(0x96fbf1a8ae78d0ba, 0x5a6dd4b71f278320)); |
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EXPECT_EQ(MultiplyU64ToU128(0xfedcba9876543210, 0xfdb97531eca86420), |
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absl::MakeUint128(0xfc98c6981a413e22, 0x342d0bbf48948200)); |
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} |
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} // namespace
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