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Export of internal Abseil changes.

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--
3f04cd3c25a99df91ff913977b8c5b343532db5d by Abseil Team <absl-team@google.com>:

Stricter memory order constraints for CycleClock callback.

PiperOrigin-RevId: 242670115

--
216db48375306490f1722a11aaf33080939d9f2f by Abseil Team <absl-team@google.com>:

internal/optional.h: move macro from types/optional.h

ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS is only used within this file.
additionally check the macro with #ifdef rather than #if, fixes -Wundef
warning:
'ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS' is not defined, evaluates to 0
PiperOrigin-RevId: 242548205

--
fbe22e7d8dc5c0b3d43ac26297e97ddbaeab3d39 by Samuel Benzaquen <sbenza@google.com>:

Implement %f natively for any input.
It evaluates the input at runtime and allocates stack space accordingly.

This removes a potential fallback into snprintf, improves performance, and removes all memory allocations in this formatting path.

PiperOrigin-RevId: 242531736

--
1458f9ba2a79ef0534e46527cd34770dee54164d by Greg Falcon <gfalcon@google.com>:

Add explicit check for NVCC in compressed_tuple.h.

NVCC claims to be MSVC, but does not implement this MSVC attribute.

PiperOrigin-RevId: 242513453
GitOrigin-RevId: 3f04cd3c25a99df91ff913977b8c5b343532db5d
Change-Id: I0742e8619c5248c7607961113e406486bc0e279b
This commit is contained in:
Abseil Team 2019-04-09 08:22:32 -07:00 committed by Shaindel Schwartz
parent 044da8a29c
commit dbae8764fb
8 changed files with 78 additions and 584 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
absl/base/internal/cycleclock.cc
View file

@ -55,10 +55,23 @@ static constexpr int32_t kShift = 2;
static constexpr double kFrequencyScale = 1.0 / (1 << kShift);
static std::atomic<CycleClockSourceFunc> cycle_clock_source;
CycleClockSourceFunc LoadCycleClockSource() {
// Optimize for the common case (no callback) by first doing a relaxed load;
// this is significantly faster on non-x86 platforms.
if (cycle_clock_source.load(std::memory_order_relaxed) == nullptr) {
return nullptr;
}
// This corresponds to the store(std::memory_order_release) in
// CycleClockSource::Register, and makes sure that any updates made prior to
// registering the callback are visible to this thread before the callback is
// invoked.
return cycle_clock_source.load(std::memory_order_acquire);
}
} // namespace
int64_t CycleClock::Now() {
auto fn = cycle_clock_source.load(std::memory_order_relaxed);
auto fn = LoadCycleClockSource();
if (fn == nullptr) {
return base_internal::UnscaledCycleClock::Now() >> kShift;
}
@ -70,7 +83,8 @@ double CycleClock::Frequency() {
}
void CycleClockSource::Register(CycleClockSourceFunc source) {
cycle_clock_source.store(source, std::memory_order_relaxed);
// Corresponds to the load(std::memory_order_acquire) in LoadCycleClockSource.
cycle_clock_source.store(source, std::memory_order_release);
}
#else

6
absl/container/internal/compressed_tuple.h
View file

@ -38,13 +38,13 @@
#include "absl/utility/utility.h"
#ifdef _MSC_VER
#if defined(_MSC_VER) && !defined(__NVCC__)
// We need to mark these classes with this declspec to ensure that
// CompressedTuple happens.
#define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC __declspec(empty_bases)
#else // _MSC_VER
#else
#define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC
#endif // _MSC_VER
#endif
namespace absl {
namespace container_internal {

1
absl/strings/BUILD.bazel
View file

@ -557,7 +557,6 @@ cc_library(
visibility = ["//visibility:private"],
deps = [
":strings",
"//absl/base:bits",
"//absl/base:core_headers",
"//absl/container:inlined_vector",
"//absl/meta:type_traits",

1
absl/strings/CMakeLists.txt
View file

@ -384,7 +384,6 @@ absl_cc_library(
COPTS
${ABSL_DEFAULT_COPTS}
DEPS
absl::bits
absl::strings
absl::core_headers
absl::inlined_vector

74
absl/strings/internal/str_format/convert_test.cc
View file

@ -2,7 +2,6 @@
#include <stdarg.h>
#include <stdio.h>
#include <cmath>
#include <limits>
#include <string>
#include "gtest/gtest.h"
@ -398,8 +397,8 @@ TEST_F(FormatConvertTest, Float) {
#endif // _MSC_VER
const char *const kFormats[] = {
"%", "%.3", "%8.5", "%9", "%.5000", "%.60", "%.30", "%03",
"%+", "% ", "%-10", "%#15.3", "%#.0", "%.0", "%1$*2$", "%1$.*2$"};
"%", "%.3", "%8.5", "%9", "%.60", "%.30", "%03", "%+",
"% ", "%-10", "%#15.3", "%#.0", "%.0", "%1$*2$", "%1$.*2$"};
std::vector<double> doubles = {0.0,
-0.0,
@ -439,36 +438,12 @@ TEST_F(FormatConvertTest, Float) {
}
}
// Workaround libc bug.
// https://sourceware.org/bugzilla/show_bug.cgi?id=22142
if (StrPrint("%f", std::numeric_limits<double>::max()) !=
"1797693134862315708145274237317043567980705675258449965989174768031"
"5726078002853876058955863276687817154045895351438246423432132688946"
"4182768467546703537516986049910576551282076245490090389328944075868"
"5084551339423045832369032229481658085593321233482747978262041447231"
"68738177180919299881250404026184124858368.000000") {
for (auto &d : doubles) {
using L = std::numeric_limits<double>;
double d2 = std::abs(d);
if (d2 == L::max() || d2 == L::min() || d2 == L::denorm_min()) {
d = 0;
}
}
}
for (const char *fmt : kFormats) {
for (char f : {'f', 'F', //
'g', 'G', //
'a', 'A', //
'e', 'E'}) {
std::string fmt_str = std::string(fmt) + f;
if (fmt == absl::string_view("%.5000") && f != 'f' && f != 'F') {
// This particular test takes way too long with snprintf.
// Disable for the case we are not implementing natively.
continue;
}
for (double d : doubles) {
int i = -10;
FormatArgImpl args[2] = {FormatArgImpl(d), FormatArgImpl(i)};
@ -479,24 +454,27 @@ TEST_F(FormatConvertTest, Float) {
ASSERT_EQ(StrPrint(fmt_str.c_str(), d, i),
FormatPack(format, absl::MakeSpan(args)))
<< fmt_str << " " << StrPrint("%.18g", d) << " "
<< StrPrint("%a", d) << " " << StrPrint("%.1080f", d);
<< StrPrint("%.999f", d);
}
}
}
}
TEST_F(FormatConvertTest, LongDouble) {
#if _MSC_VER
// MSVC has a different rounding policy than us so we can't test our
// implementation against the native one there.
return;
#endif // _MSC_VER
const char *const kFormats[] = {"%", "%.3", "%8.5", "%9", "%.5000",
const char *const kFormats[] = {"%", "%.3", "%8.5", "%9",
"%.60", "%+", "% ", "%-10"};
// This value is not representable in double, but it is in long double that
// uses the extended format.
// This is to verify that we are not truncating the value mistakenly through a
// double.
long double very_precise = 10000000000000000.25L;
std::vector<long double> doubles = {
0.0,
-0.0,
very_precise,
1 / very_precise,
std::numeric_limits<long double>::max(),
-std::numeric_limits<long double>::max(),
std::numeric_limits<long double>::min(),
@ -504,44 +482,22 @@ TEST_F(FormatConvertTest, LongDouble) {
std::numeric_limits<long double>::infinity(),
-std::numeric_limits<long double>::infinity()};
for (long double base : {1.L, 12.L, 123.L, 1234.L, 12345.L, 123456.L,
1234567.L, 12345678.L, 123456789.L, 1234567890.L,
12345678901.L, 123456789012.L, 1234567890123.L,
// This value is not representable in double, but it
// is in long double that uses the extended format.
// This is to verify that we are not truncating the
// value mistakenly through a double.
10000000000000000.25L}) {
for (int exp : {-1000, -500, 0, 500, 1000}) {
for (int sign : {1, -1}) {
doubles.push_back(sign * std::ldexp(base, exp));
doubles.push_back(sign / std::ldexp(base, exp));
}
}
}
for (const char *fmt : kFormats) {
for (char f : {'f', 'F', //
'g', 'G', //
'a', 'A', //
'e', 'E'}) {
std::string fmt_str = std::string(fmt) + 'L' + f;
if (fmt == absl::string_view("%.5000") && f != 'f' && f != 'F') {
// This particular test takes way too long with snprintf.
// Disable for the case we are not implementing natively.
continue;
}
for (auto d : doubles) {
FormatArgImpl arg(d);
UntypedFormatSpecImpl format(fmt_str);
// We use ASSERT_EQ here because failures are usually correlated and a
// bug would print way too many failed expectations causing the test to
// time out.
ASSERT_EQ(StrPrint(fmt_str.c_str(), d), FormatPack(format, {&arg, 1}))
ASSERT_EQ(StrPrint(fmt_str.c_str(), d),
FormatPack(format, {&arg, 1}))
<< fmt_str << " " << StrPrint("%.18Lg", d) << " "
<< StrPrint("%La", d) << " " << StrPrint("%.1080Lf", d);
<< StrPrint("%.999Lf", d);
}
}
}

497
absl/strings/internal/str_format/float_conversion.cc
View file

@ -2,476 +2,15 @@
#include <string.h>
#include <algorithm>
#include <array>
#include <cassert>
#include <cmath>
#include <limits>
#include <string>
#include "absl/base/attributes.h"
#include "absl/base/internal/bits.h"
#include "absl/base/optimization.h"
#include "absl/meta/type_traits.h"
#include "absl/numeric/int128.h"
#include "absl/types/span.h"
namespace absl {
namespace str_format_internal {
namespace {
// Calculates `10 * (*v) + carry` and stores the result in `*v` and returns
// the carry.
template <typename Int>
inline Int MultiplyBy10WithCarry(Int *v, Int carry) {
using NextInt = absl::conditional_t<sizeof(Int) == 4, uint64_t, uint128>;
static_assert(sizeof(void *) >= sizeof(Int),
"Don't want to use uint128 in 32-bit mode. It is too slow.");
NextInt tmp = 10 * static_cast<NextInt>(*v) + carry;
*v = static_cast<Int>(tmp);
return static_cast<Int>(tmp >> (sizeof(Int) * 8));
}
// Calculates `(2^64 * carry + *v) / 10`.
// Stores the quotient in `*v` and returns the remainder.
// Requires: `0 <= carry <= 9`
inline uint64_t DivideBy10WithCarry(uint64_t *v, uint64_t carry) {
constexpr uint64_t divisor = 10;
// 2^64 / divisor = word_quotient + word_remainder / divisor
constexpr uint64_t word_quotient = (uint64_t{1} << 63) / (divisor / 2);
constexpr uint64_t word_remainder = uint64_t{} - word_quotient * divisor;
const uint64_t mod = *v % divisor;
const uint64_t next_carry = word_remainder * carry + mod;
*v = *v / divisor + carry * word_quotient + next_carry / divisor;
return next_carry % divisor;
}
int LeadingZeros(uint64_t v) { return base_internal::CountLeadingZeros64(v); }
int LeadingZeros(uint128 v) {
auto high = static_cast<uint64_t>(v >> 64);
auto low = static_cast<uint64_t>(v);
return high != 0 ? base_internal::CountLeadingZeros64(high)
: 64 + base_internal::CountLeadingZeros64(low);
}
int TrailingZeros(uint64_t v) {
return base_internal::CountTrailingZerosNonZero64(v);
}
int TrailingZeros(uint128 v) {
auto high = static_cast<uint64_t>(v >> 64);
auto low = static_cast<uint64_t>(v);
return low == 0 ? 64 + base_internal::CountTrailingZerosNonZero64(high)
: base_internal::CountTrailingZerosNonZero64(low);
}
// The buffer must have an extra digit that is known to not need rounding.
// This is done below by having an extra '0' digit on the left.
void RoundUp(char *last_digit) {
char *p = last_digit;
while (*p == '9' || *p == '.') {
if (*p == '9') *p = '0';
--p;
}
++*p;
}
void RoundToEven(char *last_digit) {
char *p = last_digit;
if (*p == '.') --p;
if (*p % 2 == 1) RoundUp(p);
}
char *PrintIntegralDigitsFromRightDynamic(uint128 v, Span<uint32_t> array,
int exp, char *p) {
if (v == 0) {
*--p = '0';
return p;
}
int w = exp / 32;
const int offset = exp % 32;
// Left shift v by exp bits.
array[w] = static_cast<uint32_t>(v << offset);
for (v >>= (32 - offset); v; v >>= 32) array[++w] = static_cast<uint32_t>(v);
// While we have more than one word available, go in chunks of 1e9.
// We are guaranteed to have at least those many digits.
// `w` holds the largest populated word, so keep it updated.
while (w > 0) {
uint32_t carry = 0;
for (int i = w; i >= 0; --i) {
uint64_t tmp = uint64_t{array[i]} + (uint64_t{carry} << 32);
array[i] = tmp / uint64_t{1000000000};
carry = tmp % uint64_t{1000000000};
}
// If the highest word is now empty, remove it from view.
if (array[w] == 0) --w;
for (int i = 0; i < 9; ++i, carry /= 10) {
*--p = carry % 10 + '0';
}
}
// Print the leftover of the last word.
for (auto last = array[0]; last != 0; last /= 10) {
*--p = last % 10 + '0';
}
return p;
}
struct FractionalResult {
const char *end;
int precision;
};
FractionalResult PrintFractionalDigitsDynamic(uint128 v, Span<uint32_t> array,
char *p, int exp, int precision) {
int w = exp / 32;
const int offset = exp % 32;
// Right shift `v` by `exp` bits.
array[w] = static_cast<uint32_t>(v << (32 - offset));
v >>= offset;
// Make sure we don't overflow the array. We already calculated that non-zero
// bits fit, so we might not have space for leading zero bits.
for (int pos = w; v; v >>= 32) array[--pos] = static_cast<uint32_t>(v);
// Multiply the whole sequence by 10.
// On each iteration, the leftover carry word is the next digit.
// `w` holds the largest populated word, so keep it updated.
for (; w >= 0 && precision > 0; --precision) {
uint32_t carry = 0;
for (int i = w; i >= 0; --i) {
carry = MultiplyBy10WithCarry(&array[i], carry);
}
// If the lowest word is now empty, remove it from view.
if (array[w] == 0) --w;
*p++ = carry + '0';
}
constexpr uint32_t threshold = 0x80000000;
if (array[0] < threshold) {
// We round down, so nothing to do.
} else if (array[0] > threshold ||
std::any_of(&array[1], &array[w + 1],
[](uint32_t word) { return word != 0; })) {
RoundUp(p - 1);
} else {
RoundToEven(p - 1);
}
return {p, precision};
}
// Generic digit printer.
// `bits` determines how many bits of termporary space it needs for the
// calcualtions.
template <int bits, typename = void>
class DigitPrinter {
static constexpr int kInts = (bits + 31) / 32;
public:
// Quick upper bound for the number of decimal digits we need.
// This would be std::ceil(std::log10(std::pow(2, bits))), but that is not
// constexpr.
static constexpr int kDigits10 = 1 + (bits + 9) / 10 * 3 + bits / 900;
using InputType = uint128;
static char *PrintIntegralDigitsFromRight(InputType v, int exp, char *end) {
std::array<uint32_t, kInts> array{};
return PrintIntegralDigitsFromRightDynamic(v, absl::MakeSpan(array), exp,
end);
}
static FractionalResult PrintFractionalDigits(InputType v, char *p, int exp,
int precision) {
std::array<uint32_t, kInts> array{};
return PrintFractionalDigitsDynamic(v, absl::MakeSpan(array), p, exp,
precision);
}
};
// Specialiation for 64-bit working space.
// This is a performance optimization over the generic primary template.
// Only enabled in 64-bit platforms. The generic one is faster in 32-bit
// platforms.
template <int bits>
class DigitPrinter<bits, absl::enable_if_t<bits == 64 && (sizeof(void *) >=
sizeof(uint64_t))>> {
public:
static constexpr size_t kDigits10 = 20;
using InputType = uint64_t;
static char *PrintIntegralDigitsFromRight(uint64_t v, int exp, char *p) {
v <<= exp;
do {
*--p = DivideBy10WithCarry(&v, 0) + '0';
} while (v != 0);
return p;
}
static FractionalResult PrintFractionalDigits(uint64_t v, char *p, int exp,
int precision) {
v <<= (64 - exp);
while (precision > 0) {
if (!v) return {p, precision};
*p++ = MultiplyBy10WithCarry(&v, uint64_t{}) + '0';
--precision;
}
// We need to round.
if (v < 0x8000000000000000) {
// We round down, so nothing to do.
} else if (v > 0x8000000000000000) {
// We round up.
RoundUp(p - 1);
} else {
RoundToEven(p - 1);
}
assert(precision == 0);
// Precision can only be zero here. Return a constant instead.
return {p, 0};
}
};
// Specialiation for 128-bit working space.
// This is a performance optimization over the generic primary template.
template <int bits>
class DigitPrinter<bits, absl::enable_if_t<bits == 128 && (sizeof(void *) >=
sizeof(uint64_t))>> {
public:
static constexpr size_t kDigits10 = 40;
using InputType = uint128;
static char *PrintIntegralDigitsFromRight(uint128 v, int exp, char *p) {
v <<= exp;
auto high = static_cast<uint64_t>(v >> 64);
auto low = static_cast<uint64_t>(v);
do {
uint64_t carry = DivideBy10WithCarry(&high, 0);
carry = DivideBy10WithCarry(&low, carry);
*--p = carry + '0';
} while (high != 0u);
while (low != 0u) {
*--p = DivideBy10WithCarry(&low, 0) + '0';
}
return p;
}
static FractionalResult PrintFractionalDigits(uint128 v, char *p, int exp,
int precision) {
v <<= (128 - exp);
auto high = static_cast<uint64_t>(v >> 64);
auto low = static_cast<uint64_t>(v);
// While we have digits to print and `low` is not empty, do the long
// multiplication.
while (precision > 0 && low != 0) {
uint64_t carry = MultiplyBy10WithCarry(&low, uint64_t{});
carry = MultiplyBy10WithCarry(&high, carry);
*p++ = carry + '0';
--precision;
}
// Now `low` is empty, so use a faster approach for the rest of the digits.
// This block is pretty much the same as the main loop for the 64-bit case
// above.
while (precision > 0) {
if (!high) return {p, precision};
*p++ = MultiplyBy10WithCarry(&high, uint64_t{}) + '0';
--precision;
}
// We need to round.
if (high < 0x8000000000000000) {
// We round down, so nothing to do.
} else if (high > 0x8000000000000000 || low != 0) {
// We round up.
RoundUp(p - 1);
} else {
RoundToEven(p - 1);
}
assert(precision == 0);
// Precision can only be zero here. Return a constant instead.
return {p, 0};
}
};
struct FormatState {
char sign_char;
int precision;
const ConversionSpec &conv;
FormatSinkImpl *sink;
};
void FinalPrint(string_view data, int trailing_zeros,
const FormatState &state) {
if (state.conv.width() < 0) {
// No width specified. Fast-path.
if (state.sign_char != '\0') state.sink->Append(1, state.sign_char);
state.sink->Append(data);
state.sink->Append(trailing_zeros, '0');
return;
}
int left_spaces = 0, zeros = 0, right_spaces = 0;
int total_size = (state.sign_char != 0 ? 1 : 0) +
static_cast<int>(data.size()) + trailing_zeros;
int missing_chars = std::max(state.conv.width() - total_size, 0);
if (state.conv.flags().left) {
right_spaces = missing_chars;
} else if (state.conv.flags().zero) {
zeros = missing_chars;
} else {
left_spaces = missing_chars;
}
state.sink->Append(left_spaces, ' ');
if (state.sign_char != '\0') state.sink->Append(1, state.sign_char);
state.sink->Append(zeros, '0');
state.sink->Append(data);
state.sink->Append(trailing_zeros, '0');
state.sink->Append(right_spaces, ' ');
}
template <int num_bits, typename Int>
void FormatFPositiveExp(Int v, int exp, const FormatState &state) {
using IntegralPrinter = DigitPrinter<num_bits>;
char buffer[IntegralPrinter::kDigits10 + /* . */ 1];
buffer[IntegralPrinter::kDigits10] = '.';
const char *digits = IntegralPrinter::PrintIntegralDigitsFromRight(
static_cast<typename IntegralPrinter::InputType>(v), exp,
buffer + sizeof(buffer) - 1);
size_t size = buffer + sizeof(buffer) - digits;
// In `alt` mode (flag #) we keep the `.` even if there are no fractional
// digits. In non-alt mode, we strip it.
if (ABSL_PREDICT_FALSE(state.precision == 0 && !state.conv.flags().alt)) {
--size;
}
FinalPrint(string_view(digits, size), state.precision, state);
}
template <int num_bits, typename Int>
void FormatFNegativeExp(Int v, int exp, const FormatState &state) {
constexpr int input_bits = sizeof(Int) * 8;
using IntegralPrinter = DigitPrinter<input_bits>;
using FractionalPrinter = DigitPrinter<num_bits>;
static constexpr size_t integral_size =
1 + /* in case we need to round up an extra digit */
IntegralPrinter::kDigits10 + 1;
char buffer[integral_size + /* . */ 1 + num_bits];
buffer[integral_size] = '.';
char *const integral_digits_end = buffer + integral_size;
char *integral_digits_start;
char *const fractional_digits_start = buffer + integral_size + 1;
if (exp < input_bits) {
integral_digits_start = IntegralPrinter::PrintIntegralDigitsFromRight(
v >> exp, 0, integral_digits_end);
} else {
integral_digits_start = integral_digits_end - 1;
*integral_digits_start = '0';
}
// PrintFractionalDigits may pull a carried 1 all the way up through the
// integral portion.
integral_digits_start[-1] = '0';
auto fractional_result = FractionalPrinter::PrintFractionalDigits(
static_cast<typename FractionalPrinter::InputType>(v),
fractional_digits_start, exp, state.precision);
if (integral_digits_start[-1] != '0') --integral_digits_start;
size_t size = fractional_result.end - integral_digits_start;
// In `alt` mode (flag #) we keep the `.` even if there are no fractional
// digits. In non-alt mode, we strip it.
if (ABSL_PREDICT_FALSE(state.precision == 0 && !state.conv.flags().alt)) {
--size;
}
FinalPrint(string_view(integral_digits_start, size),
fractional_result.precision, state);
}
template <typename Int>
void FormatF(Int mantissa, int exp, const FormatState &state) {
// Remove trailing zeros as they are not useful.
// This helps use faster implementations/less stack space in some cases.
if (mantissa != 0) {
int trailing = TrailingZeros(mantissa);
mantissa >>= trailing;
exp += trailing;
}
// The table driven dispatch gives us two benefits: fast distpatch and
// prevent inlining.
// We must not inline any of the functions below (other than the ones for
// 64-bit) to avoid blowing up this stack frame.
if (exp >= 0) {
// We will left shift the mantissa. Calculate how many bits we need.
// Special case 64-bit as we will use a uint64_t for it. Use a table for the
// rest and unconditionally use uint128.
const int total_bits = sizeof(Int) * 8 - LeadingZeros(mantissa) + exp;
if (total_bits <= 64) {
return FormatFPositiveExp<64>(mantissa, exp, state);
} else {
using Formatter = void (*)(uint128, int, const FormatState &);
static constexpr Formatter kFormatters[] = {
FormatFPositiveExp<1 << 7>, FormatFPositiveExp<1 << 8>,
FormatFPositiveExp<1 << 9>, FormatFPositiveExp<1 << 10>,
FormatFPositiveExp<1 << 11>, FormatFPositiveExp<1 << 12>,
FormatFPositiveExp<1 << 13>, FormatFPositiveExp<1 << 14>,
FormatFPositiveExp<1 << 15>,
};
static constexpr int max_total_bits =
sizeof(Int) * 8 + std::numeric_limits<long double>::max_exponent;
assert(total_bits <= max_total_bits);
static_assert(max_total_bits <= (1 << 15), "");
const int log2 =
64 - LeadingZeros((static_cast<uint64_t>(total_bits) - 1) / 128);
assert(log2 < std::end(kFormatters) - std::begin(kFormatters));
kFormatters[log2](mantissa, exp, state);
}
} else {
exp = -exp;
// We know we don't need more than Int itself for the integral part.
// We need `precision` fractional digits, but there are at most `exp`
// non-zero digits after the decimal point. The rest will be zeros.
// Special case 64-bit as we will use a uint64_t for it. Use a table for the
// rest and unconditionally use uint128.
if (exp <= 64) {
return FormatFNegativeExp<64>(mantissa, exp, state);
} else {
using Formatter = void (*)(uint128, int, const FormatState &);
static constexpr Formatter kFormatters[] = {
FormatFNegativeExp<1 << 7>, FormatFNegativeExp<1 << 8>,
FormatFNegativeExp<1 << 9>, FormatFNegativeExp<1 << 10>,
FormatFNegativeExp<1 << 11>, FormatFNegativeExp<1 << 12>,
FormatFNegativeExp<1 << 13>, FormatFNegativeExp<1 << 14>};
static_assert(
-std::numeric_limits<long double>::min_exponent <= (1 << 14), "");
const int log2 =
64 - LeadingZeros((static_cast<uint64_t>(exp) - 1) / 128);
assert(log2 < std::end(kFormatters) - std::begin(kFormatters));
kFormatters[log2](mantissa, exp, state);
}
}
}
char *CopyStringTo(string_view v, char *out) {
std::memcpy(out, v.data(), v.size());
return out + v.size();
@ -556,7 +95,7 @@ template <typename Float>
bool ConvertNonNumericFloats(char sign_char, Float v,
const ConversionSpec &conv, FormatSinkImpl *sink) {
char text[4], *ptr = text;
if (sign_char != '\0') *ptr++ = sign_char;
if (sign_char) *ptr++ = sign_char;
if (std::isnan(v)) {
ptr = std::copy_n(conv.conv().upper() ? "NAN" : "nan", 3, ptr);
} else if (std::isinf(v)) {
@ -626,12 +165,7 @@ constexpr bool CanFitMantissa() {
template <typename Float>
struct Decomposed {
using MantissaType =
absl::conditional_t<std::is_same<long double, Float>::value, uint128,
uint64_t>;
static_assert(std::numeric_limits<Float>::digits <= sizeof(MantissaType) * 8,
"");
MantissaType mantissa;
Float mantissa;
int exponent;
};
@ -642,8 +176,7 @@ Decomposed<Float> Decompose(Float v) {
Float m = std::frexp(v, &exp);
m = std::ldexp(m, std::numeric_limits<Float>::digits);
exp -= std::numeric_limits<Float>::digits;
return {static_cast<typename Decomposed<Float>::MantissaType>(m), exp};
return {m, exp};
}
// Print 'digits' as decimal.
@ -801,7 +334,7 @@ bool FloatToBuffer(Decomposed<Float> decomposed, int precision, Buffer *out,
static_cast<std::uint64_t>(decomposed.exponent), precision, out, exp))
return true;
#if defined(ABSL_HAVE_INTRINSIC_INT128)
#if defined(__SIZEOF_INT128__)
// If that is not enough, try with __uint128_t.
return CanFitMantissa<Float, __uint128_t>() &&
FloatToBufferImpl<__uint128_t, Float, mode>(
@ -829,7 +362,7 @@ void WriteBufferToSink(char sign_char, string_view str,
}
sink->Append(left_spaces, ' ');
if (sign_char != '\0') sink->Append(1, sign_char);
if (sign_char) sink->Append(1, sign_char);
sink->Append(zeros, '0');
sink->Append(str);
sink->Append(right_spaces, ' ');
@ -866,9 +399,12 @@ bool FloatToSink(const Float v, const ConversionSpec &conv,
switch (conv.conv().id()) {
case ConversionChar::f:
case ConversionChar::F:
FormatF(decomposed.mantissa, decomposed.exponent,
{sign_char, precision, conv, sink});
return true;
if (!FloatToBuffer<FormatStyle::Fixed>(decomposed, precision, &buffer,
nullptr)) {
return FallbackToSnprintf(v, conv, sink);
}
if (!conv.flags().alt && buffer.back() == '.') buffer.pop_back();
break;
case ConversionChar::e:
case ConversionChar::E:
@ -930,22 +466,11 @@ bool FloatToSink(const Float v, const ConversionSpec &conv,
bool ConvertFloatImpl(long double v, const ConversionSpec &conv,
FormatSinkImpl *sink) {
if (std::numeric_limits<long double>::digits ==
2 * std::numeric_limits<double>::digits) {
// This is the `double-double` representation of `long double`.
// We do not handle it natively. Fallback to snprintf.
return FallbackToSnprintf(v, conv, sink);
}
return FloatToSink(v, conv, sink);
}
bool ConvertFloatImpl(float v, const ConversionSpec &conv,
FormatSinkImpl *sink) {
// DivideBy10WithCarry is not actually used in some builds. This here silences
// the "unused" warning. We just need to put it in any function that is really
// used.
(void)&DivideBy10WithCarry;
return FloatToSink(v, conv, sink);
}

36
absl/types/internal/optional.h
View file

@ -25,6 +25,34 @@
#include "absl/meta/type_traits.h"
#include "absl/utility/utility.h"
// ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
//
// Inheriting constructors is supported in GCC 4.8+, Clang 3.3+ and MSVC 2015.
// __cpp_inheriting_constructors is a predefined macro and a recommended way to
// check for this language feature, but GCC doesn't support it until 5.0 and
// Clang doesn't support it until 3.6.
// Also, MSVC 2015 has a bug: it doesn't inherit the constexpr template
// constructor. For example, the following code won't work on MSVC 2015 Update3:
// struct Base {
// int t;
// template <typename T>
// constexpr Base(T t_) : t(t_) {}
// };
// struct Foo : Base {
// using Base::Base;
// }
// constexpr Foo foo(0); // doesn't work on MSVC 2015
#if defined(__clang__)
#if __has_feature(cxx_inheriting_constructors)
#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
#endif
#elif (defined(__GNUC__) && \
(__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 8)) || \
(__cpp_inheriting_constructors >= 200802) || \
(defined(_MSC_VER) && _MSC_VER >= 1910)
#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
#endif
namespace absl {
// Forward declaration
@ -108,7 +136,7 @@ template <typename T>
class optional_data_base : public optional_data_dtor_base<T> {
protected:
using base = optional_data_dtor_base<T>;
#if ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
#ifdef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
using base::base;
#else
optional_data_base() = default;
@ -151,7 +179,7 @@ class optional_data;
template <typename T>
class optional_data<T, true> : public optional_data_base<T> {
protected:
#if ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
#ifdef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
using optional_data_base<T>::optional_data_base;
#else
optional_data() = default;
@ -165,7 +193,7 @@ class optional_data<T, true> : public optional_data_base<T> {
template <typename T>
class optional_data<T, false> : public optional_data_base<T> {
protected:
#if ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
#ifdef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
using optional_data_base<T>::optional_data_base;
#else
template <typename... Args>
@ -361,4 +389,6 @@ struct optional_hash_base<T, decltype(std::hash<absl::remove_const_t<T> >()(
} // namespace optional_internal
} // namespace absl
#undef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
#endif // ABSL_TYPES_INTERNAL_OPTIONAL_H_

29
absl/types/optional.h
View file

@ -64,34 +64,6 @@ using std::nullopt;
#include "absl/types/bad_optional_access.h"
#include "absl/types/internal/optional.h"
// ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
//
// Inheriting constructors is supported in GCC 4.8+, Clang 3.3+ and MSVC 2015.
// __cpp_inheriting_constructors is a predefined macro and a recommended way to
// check for this language feature, but GCC doesn't support it until 5.0 and
// Clang doesn't support it until 3.6.
// Also, MSVC 2015 has a bug: it doesn't inherit the constexpr template
// constructor. For example, the following code won't work on MSVC 2015 Update3:
// struct Base {
// int t;
// template <typename T>
// constexpr Base(T t_) : t(t_) {}
// };
// struct Foo : Base {
// using Base::Base;
// }
// constexpr Foo foo(0); // doesn't work on MSVC 2015
#if defined(__clang__)
#if __has_feature(cxx_inheriting_constructors)
#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
#endif
#elif (defined(__GNUC__) && \
(__GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 8)) || \
(__cpp_inheriting_constructors >= 200802) || \
(defined(_MSC_VER) && _MSC_VER >= 1910)
#define ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS 1
#endif
namespace absl {
// nullopt_t
@ -791,7 +763,6 @@ struct hash<absl::optional<T> >
} // namespace std
#undef ABSL_OPTIONAL_USE_INHERITING_CONSTRUCTORS
#undef ABSL_MSVC_CONSTEXPR_BUG_IN_UNION_LIKE_CLASS
#endif // ABSL_HAVE_STD_OPTIONAL