Squashed 'third_party/abseil/' content from commit ddf8e52a2
Change-Id: I330cdc687395c6605ad027b855e313ff4a2059e9
git-subtree-dir: third_party/abseil
git-subtree-split: ddf8e52a2918dd0ccec75d3e2426125fa3926724
diff --git a/absl/numeric/int128.cc b/absl/numeric/int128.cc
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+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/numeric/int128.h"
+
+#include <stddef.h>
+#include <cassert>
+#include <iomanip>
+#include <ostream> // NOLINT(readability/streams)
+#include <sstream>
+#include <string>
+#include <type_traits>
+
+namespace absl {
+
+const uint128 kuint128max = MakeUint128(std::numeric_limits<uint64_t>::max(),
+ std::numeric_limits<uint64_t>::max());
+
+namespace {
+
+// Returns the 0-based position of the last set bit (i.e., most significant bit)
+// in the given uint64_t. The argument may not be 0.
+//
+// For example:
+// Given: 5 (decimal) == 101 (binary)
+// Returns: 2
+#define STEP(T, n, pos, sh) \
+ do { \
+ if ((n) >= (static_cast<T>(1) << (sh))) { \
+ (n) = (n) >> (sh); \
+ (pos) |= (sh); \
+ } \
+ } while (0)
+static inline int Fls64(uint64_t n) {
+ assert(n != 0);
+ int pos = 0;
+ STEP(uint64_t, n, pos, 0x20);
+ uint32_t n32 = static_cast<uint32_t>(n);
+ STEP(uint32_t, n32, pos, 0x10);
+ STEP(uint32_t, n32, pos, 0x08);
+ STEP(uint32_t, n32, pos, 0x04);
+ return pos + ((uint64_t{0x3333333322221100} >> (n32 << 2)) & 0x3);
+}
+#undef STEP
+
+// Like Fls64() above, but returns the 0-based position of the last set bit
+// (i.e., most significant bit) in the given uint128. The argument may not be 0.
+static inline int Fls128(uint128 n) {
+ if (uint64_t hi = Uint128High64(n)) {
+ return Fls64(hi) + 64;
+ }
+ return Fls64(Uint128Low64(n));
+}
+
+// Long division/modulo for uint128 implemented using the shift-subtract
+// division algorithm adapted from:
+// https://stackoverflow.com/questions/5386377/division-without-using
+void DivModImpl(uint128 dividend, uint128 divisor, uint128* quotient_ret,
+ uint128* remainder_ret) {
+ assert(divisor != 0);
+
+ if (divisor > dividend) {
+ *quotient_ret = 0;
+ *remainder_ret = dividend;
+ return;
+ }
+
+ if (divisor == dividend) {
+ *quotient_ret = 1;
+ *remainder_ret = 0;
+ return;
+ }
+
+ uint128 denominator = divisor;
+ uint128 quotient = 0;
+
+ // Left aligns the MSB of the denominator and the dividend.
+ const int shift = Fls128(dividend) - Fls128(denominator);
+ denominator <<= shift;
+
+ // Uses shift-subtract algorithm to divide dividend by denominator. The
+ // remainder will be left in dividend.
+ for (int i = 0; i <= shift; ++i) {
+ quotient <<= 1;
+ if (dividend >= denominator) {
+ dividend -= denominator;
+ quotient |= 1;
+ }
+ denominator >>= 1;
+ }
+
+ *quotient_ret = quotient;
+ *remainder_ret = dividend;
+}
+
+template <typename T>
+uint128 MakeUint128FromFloat(T v) {
+ static_assert(std::is_floating_point<T>::value, "");
+
+ // Rounding behavior is towards zero, same as for built-in types.
+
+ // Undefined behavior if v is NaN or cannot fit into uint128.
+ assert(std::isfinite(v) && v > -1 &&
+ (std::numeric_limits<T>::max_exponent <= 128 ||
+ v < std::ldexp(static_cast<T>(1), 128)));
+
+ if (v >= std::ldexp(static_cast<T>(1), 64)) {
+ uint64_t hi = static_cast<uint64_t>(std::ldexp(v, -64));
+ uint64_t lo = static_cast<uint64_t>(v - std::ldexp(static_cast<T>(hi), 64));
+ return MakeUint128(hi, lo);
+ }
+
+ return MakeUint128(0, static_cast<uint64_t>(v));
+}
+
+#if defined(__clang__) && !defined(__SSE3__)
+// Workaround for clang bug: https://bugs.llvm.org/show_bug.cgi?id=38289
+// Casting from long double to uint64_t is miscompiled and drops bits.
+// It is more work, so only use when we need the workaround.
+uint128 MakeUint128FromFloat(long double v) {
+ // Go 50 bits at a time, that fits in a double
+ static_assert(std::numeric_limits<double>::digits >= 50, "");
+ static_assert(std::numeric_limits<long double>::digits <= 150, "");
+ // Undefined behavior if v is not finite or cannot fit into uint128.
+ assert(std::isfinite(v) && v > -1 && v < std::ldexp(1.0L, 128));
+
+ v = std::ldexp(v, -100);
+ uint64_t w0 = static_cast<uint64_t>(static_cast<double>(std::trunc(v)));
+ v = std::ldexp(v - static_cast<double>(w0), 50);
+ uint64_t w1 = static_cast<uint64_t>(static_cast<double>(std::trunc(v)));
+ v = std::ldexp(v - static_cast<double>(w1), 50);
+ uint64_t w2 = static_cast<uint64_t>(static_cast<double>(std::trunc(v)));
+ return (static_cast<uint128>(w0) << 100) | (static_cast<uint128>(w1) << 50) |
+ static_cast<uint128>(w2);
+}
+#endif // __clang__ && !__SSE3__
+} // namespace
+
+uint128::uint128(float v) : uint128(MakeUint128FromFloat(v)) {}
+uint128::uint128(double v) : uint128(MakeUint128FromFloat(v)) {}
+uint128::uint128(long double v) : uint128(MakeUint128FromFloat(v)) {}
+
+uint128 operator/(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+ return static_cast<unsigned __int128>(lhs) /
+ static_cast<unsigned __int128>(rhs);
+#else // ABSL_HAVE_INTRINSIC_INT128
+ uint128 quotient = 0;
+ uint128 remainder = 0;
+ DivModImpl(lhs, rhs, "ient, &remainder);
+ return quotient;
+#endif // ABSL_HAVE_INTRINSIC_INT128
+}
+uint128 operator%(uint128 lhs, uint128 rhs) {
+#if defined(ABSL_HAVE_INTRINSIC_INT128)
+ return static_cast<unsigned __int128>(lhs) %
+ static_cast<unsigned __int128>(rhs);
+#else // ABSL_HAVE_INTRINSIC_INT128
+ uint128 quotient = 0;
+ uint128 remainder = 0;
+ DivModImpl(lhs, rhs, "ient, &remainder);
+ return remainder;
+#endif // ABSL_HAVE_INTRINSIC_INT128
+}
+
+namespace {
+
+std::string Uint128ToFormattedString(uint128 v, std::ios_base::fmtflags flags) {
+ // Select a divisor which is the largest power of the base < 2^64.
+ uint128 div;
+ int div_base_log;
+ switch (flags & std::ios::basefield) {
+ case std::ios::hex:
+ div = 0x1000000000000000; // 16^15
+ div_base_log = 15;
+ break;
+ case std::ios::oct:
+ div = 01000000000000000000000; // 8^21
+ div_base_log = 21;
+ break;
+ default: // std::ios::dec
+ div = 10000000000000000000u; // 10^19
+ div_base_log = 19;
+ break;
+ }
+
+ // Now piece together the uint128 representation from three chunks of the
+ // original value, each less than "div" and therefore representable as a
+ // uint64_t.
+ std::ostringstream os;
+ std::ios_base::fmtflags copy_mask =
+ std::ios::basefield | std::ios::showbase | std::ios::uppercase;
+ os.setf(flags & copy_mask, copy_mask);
+ uint128 high = v;
+ uint128 low;
+ DivModImpl(high, div, &high, &low);
+ uint128 mid;
+ DivModImpl(high, div, &high, &mid);
+ if (Uint128Low64(high) != 0) {
+ os << Uint128Low64(high);
+ os << std::noshowbase << std::setfill('0') << std::setw(div_base_log);
+ os << Uint128Low64(mid);
+ os << std::setw(div_base_log);
+ } else if (Uint128Low64(mid) != 0) {
+ os << Uint128Low64(mid);
+ os << std::noshowbase << std::setfill('0') << std::setw(div_base_log);
+ }
+ os << Uint128Low64(low);
+ return os.str();
+}
+
+} // namespace
+
+std::ostream& operator<<(std::ostream& os, uint128 v) {
+ std::ios_base::fmtflags flags = os.flags();
+ std::string rep = Uint128ToFormattedString(v, flags);
+
+ // Add the requisite padding.
+ std::streamsize width = os.width(0);
+ if (static_cast<size_t>(width) > rep.size()) {
+ std::ios::fmtflags adjustfield = flags & std::ios::adjustfield;
+ if (adjustfield == std::ios::left) {
+ rep.append(width - rep.size(), os.fill());
+ } else if (adjustfield == std::ios::internal &&
+ (flags & std::ios::showbase) &&
+ (flags & std::ios::basefield) == std::ios::hex && v != 0) {
+ rep.insert(2, width - rep.size(), os.fill());
+ } else {
+ rep.insert(0, width - rep.size(), os.fill());
+ }
+ }
+
+ return os << rep;
+}
+
+} // namespace absl
+
+namespace std {
+constexpr bool numeric_limits<absl::uint128>::is_specialized;
+constexpr bool numeric_limits<absl::uint128>::is_signed;
+constexpr bool numeric_limits<absl::uint128>::is_integer;
+constexpr bool numeric_limits<absl::uint128>::is_exact;
+constexpr bool numeric_limits<absl::uint128>::has_infinity;
+constexpr bool numeric_limits<absl::uint128>::has_quiet_NaN;
+constexpr bool numeric_limits<absl::uint128>::has_signaling_NaN;
+constexpr float_denorm_style numeric_limits<absl::uint128>::has_denorm;
+constexpr bool numeric_limits<absl::uint128>::has_denorm_loss;
+constexpr float_round_style numeric_limits<absl::uint128>::round_style;
+constexpr bool numeric_limits<absl::uint128>::is_iec559;
+constexpr bool numeric_limits<absl::uint128>::is_bounded;
+constexpr bool numeric_limits<absl::uint128>::is_modulo;
+constexpr int numeric_limits<absl::uint128>::digits;
+constexpr int numeric_limits<absl::uint128>::digits10;
+constexpr int numeric_limits<absl::uint128>::max_digits10;
+constexpr int numeric_limits<absl::uint128>::radix;
+constexpr int numeric_limits<absl::uint128>::min_exponent;
+constexpr int numeric_limits<absl::uint128>::min_exponent10;
+constexpr int numeric_limits<absl::uint128>::max_exponent;
+constexpr int numeric_limits<absl::uint128>::max_exponent10;
+constexpr bool numeric_limits<absl::uint128>::traps;
+constexpr bool numeric_limits<absl::uint128>::tinyness_before;
+} // namespace std