[PATCH 1/5] libstdc++: Import the fast_float library

Patrick Palka ppalka@redhat.com
Tue Nov 16 00:25:01 GMT 2021


This copies the fast_float library[1] into the compiled-in library
sources.  We're going to use this library in our floating-point
std::from_chars implementation for faster and more portable parsing of
binary32/64 decimal strings.

[1]: https://github.com/fastfloat/fast_float

Series tested on x86_64, i686, ppc64, ppc64le and aarch64, does it
look OK for trunk?

libstdc++-v3/ChangeLog:

	* src/c++17/fast_float/LICENSE-APACHE: New file.
	* src/c++17/fast_float/LICENSE-MIT: New file.
	* src/c++17/fast_float/LOCAL_PATCHES: New file.
	* src/c++17/fast_float/MERGE: New file.
	* src/c++17/fast_float/ascii_number.h,
	src/c++17/fast_float/bigint.h,
	src/c++17/fast_float/decimal_to_binary.h,
	src/c++17/fast_float/digit_comparison.h,
	src/c++17/fast_float/fast_float.h,
	src/c++17/fast_float/fast_table.h,
	src/c++17/fast_float/float_common.h,
	src/c++17/fast_float/parse_number.h: Import these files from the
	fast_float library.
---
 .../src/c++17/fast_float/LICENSE-APACHE       | 190 +++++
 libstdc++-v3/src/c++17/fast_float/LICENSE-MIT |  27 +
 .../src/c++17/fast_float/LOCAL_PATCHES        |   0
 libstdc++-v3/src/c++17/fast_float/MERGE       |   4 +
 .../src/c++17/fast_float/ascii_number.h       | 231 ++++++
 libstdc++-v3/src/c++17/fast_float/bigint.h    | 590 +++++++++++++++
 .../src/c++17/fast_float/decimal_to_binary.h  | 194 +++++
 .../src/c++17/fast_float/digit_comparison.h   | 423 +++++++++++
 .../src/c++17/fast_float/fast_float.h         |  63 ++
 .../src/c++17/fast_float/fast_table.h         | 699 ++++++++++++++++++
 .../src/c++17/fast_float/float_common.h       | 362 +++++++++
 .../src/c++17/fast_float/parse_number.h       | 113 +++
 12 files changed, 2896 insertions(+)
 create mode 100644 libstdc++-v3/src/c++17/fast_float/LICENSE-APACHE
 create mode 100644 libstdc++-v3/src/c++17/fast_float/LICENSE-MIT
 create mode 100644 libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES
 create mode 100644 libstdc++-v3/src/c++17/fast_float/MERGE
 create mode 100644 libstdc++-v3/src/c++17/fast_float/ascii_number.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/bigint.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/decimal_to_binary.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/digit_comparison.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/fast_float.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/fast_table.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/float_common.h
 create mode 100644 libstdc++-v3/src/c++17/fast_float/parse_number.h

diff --git a/libstdc++-v3/src/c++17/fast_float/LICENSE-APACHE b/libstdc++-v3/src/c++17/fast_float/LICENSE-APACHE
new file mode 100644
index 00000000000..26f4398f249
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/LICENSE-APACHE
@@ -0,0 +1,190 @@
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+      the conditions stated in this License.
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+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
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+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
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+   6. Trademarks. This License does not grant permission to use the trade
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+      agreed to in writing, Licensor provides the Work (and each
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+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
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+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
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+   9. Accepting Warranty or Additional Liability. While redistributing
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+   Unless required by applicable law or agreed to in writing, software
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diff --git a/libstdc++-v3/src/c++17/fast_float/LICENSE-MIT b/libstdc++-v3/src/c++17/fast_float/LICENSE-MIT
new file mode 100644
index 00000000000..2fb2a37ad7f
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/LICENSE-MIT
@@ -0,0 +1,27 @@
+MIT License
+
+Copyright (c) 2021 The fast_float authors
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
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+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES b/libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/libstdc++-v3/src/c++17/fast_float/MERGE b/libstdc++-v3/src/c++17/fast_float/MERGE
new file mode 100644
index 00000000000..43bdc3981c8
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/MERGE
@@ -0,0 +1,4 @@
+d35368cae610b4edeec61cd41e4d2367a4d33f58
+
+The first line of this file holds the git revision number of the
+last merge done from the master library sources.
diff --git a/libstdc++-v3/src/c++17/fast_float/ascii_number.h b/libstdc++-v3/src/c++17/fast_float/ascii_number.h
new file mode 100644
index 00000000000..3e6bb3e9ef3
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/ascii_number.h
@@ -0,0 +1,231 @@
+#ifndef FASTFLOAT_ASCII_NUMBER_H
+#define FASTFLOAT_ASCII_NUMBER_H
+
+#include <cctype>
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+
+#include "float_common.h"
+
+namespace fast_float {
+
+// Next function can be micro-optimized, but compilers are entirely
+// able to optimize it well.
+fastfloat_really_inline bool is_integer(char c)  noexcept  { return c >= '0' && c <= '9'; }
+
+fastfloat_really_inline uint64_t byteswap(uint64_t val) {
+  return (val & 0xFF00000000000000) >> 56
+    | (val & 0x00FF000000000000) >> 40
+    | (val & 0x0000FF0000000000) >> 24
+    | (val & 0x000000FF00000000) >> 8
+    | (val & 0x00000000FF000000) << 8
+    | (val & 0x0000000000FF0000) << 24
+    | (val & 0x000000000000FF00) << 40
+    | (val & 0x00000000000000FF) << 56;
+}
+
+fastfloat_really_inline uint64_t read_u64(const char *chars) {
+  uint64_t val;
+  ::memcpy(&val, chars, sizeof(uint64_t));
+#if FASTFLOAT_IS_BIG_ENDIAN == 1
+  // Need to read as-if the number was in little-endian order.
+  val = byteswap(val);
+#endif
+  return val;
+}
+
+fastfloat_really_inline void write_u64(uint8_t *chars, uint64_t val) {
+#if FASTFLOAT_IS_BIG_ENDIAN == 1
+  // Need to read as-if the number was in little-endian order.
+  val = byteswap(val);
+#endif
+  ::memcpy(chars, &val, sizeof(uint64_t));
+}
+
+// credit  @aqrit
+fastfloat_really_inline uint32_t  parse_eight_digits_unrolled(uint64_t val) {
+  const uint64_t mask = 0x000000FF000000FF;
+  const uint64_t mul1 = 0x000F424000000064; // 100 + (1000000ULL << 32)
+  const uint64_t mul2 = 0x0000271000000001; // 1 + (10000ULL << 32)
+  val -= 0x3030303030303030;
+  val = (val * 10) + (val >> 8); // val = (val * 2561) >> 8;
+  val = (((val & mask) * mul1) + (((val >> 16) & mask) * mul2)) >> 32;
+  return uint32_t(val);
+}
+
+fastfloat_really_inline uint32_t parse_eight_digits_unrolled(const char *chars)  noexcept  {
+  return parse_eight_digits_unrolled(read_u64(chars));
+}
+
+// credit @aqrit
+fastfloat_really_inline bool is_made_of_eight_digits_fast(uint64_t val)  noexcept  {
+  return !((((val + 0x4646464646464646) | (val - 0x3030303030303030)) &
+     0x8080808080808080));
+}
+
+fastfloat_really_inline bool is_made_of_eight_digits_fast(const char *chars)  noexcept  {
+  return is_made_of_eight_digits_fast(read_u64(chars));
+}
+
+typedef span<const char> byte_span;
+
+struct parsed_number_string {
+  int64_t exponent{0};
+  uint64_t mantissa{0};
+  const char *lastmatch{nullptr};
+  bool negative{false};
+  bool valid{false};
+  bool too_many_digits{false};
+  // contains the range of the significant digits
+  byte_span integer{};  // non-nullable
+  byte_span fraction{}; // nullable
+};
+
+// Assuming that you use no more than 19 digits, this will
+// parse an ASCII string.
+fastfloat_really_inline
+parsed_number_string parse_number_string(const char *p, const char *pend, parse_options options) noexcept {
+  const chars_format fmt = options.format;
+  const char decimal_point = options.decimal_point;
+
+  parsed_number_string answer;
+  answer.valid = false;
+  answer.too_many_digits = false;
+  answer.negative = (*p == '-');
+  if (*p == '-') { // C++17 20.19.3.(7.1) explicitly forbids '+' sign here
+    ++p;
+    if (p == pend) {
+      return answer;
+    }
+    if (!is_integer(*p) && (*p != decimal_point)) { // a sign must be followed by an integer or the dot
+      return answer;
+    }
+  }
+  const char *const start_digits = p;
+
+  uint64_t i = 0; // an unsigned int avoids signed overflows (which are bad)
+
+  while ((std::distance(p, pend) >= 8) && is_made_of_eight_digits_fast(p)) {
+    i = i * 100000000 + parse_eight_digits_unrolled(p); // in rare cases, this will overflow, but that's ok
+    p += 8;
+  }
+  while ((p != pend) && is_integer(*p)) {
+    // a multiplication by 10 is cheaper than an arbitrary integer
+    // multiplication
+    i = 10 * i +
+        uint64_t(*p - '0'); // might overflow, we will handle the overflow later
+    ++p;
+  }
+  const char *const end_of_integer_part = p;
+  int64_t digit_count = int64_t(end_of_integer_part - start_digits);
+  answer.integer = byte_span(start_digits, size_t(digit_count));
+  int64_t exponent = 0;
+  if ((p != pend) && (*p == decimal_point)) {
+    ++p;
+    const char* before = p;
+    // can occur at most twice without overflowing, but let it occur more, since
+    // for integers with many digits, digit parsing is the primary bottleneck.
+    while ((std::distance(p, pend) >= 8) && is_made_of_eight_digits_fast(p)) {
+      i = i * 100000000 + parse_eight_digits_unrolled(p); // in rare cases, this will overflow, but that's ok
+      p += 8;
+    }
+    while ((p != pend) && is_integer(*p)) {
+      uint8_t digit = uint8_t(*p - '0');
+      ++p;
+      i = i * 10 + digit; // in rare cases, this will overflow, but that's ok
+    }
+    exponent = before - p;
+    answer.fraction = byte_span(before, size_t(p - before));
+    digit_count -= exponent;
+  }
+  // we must have encountered at least one integer!
+  if (digit_count == 0) {
+    return answer;
+  }
+  int64_t exp_number = 0;            // explicit exponential part
+  if ((fmt & chars_format::scientific) && (p != pend) && (('e' == *p) || ('E' == *p))) {
+    const char * location_of_e = p;
+    ++p;
+    bool neg_exp = false;
+    if ((p != pend) && ('-' == *p)) {
+      neg_exp = true;
+      ++p;
+    } else if ((p != pend) && ('+' == *p)) { // '+' on exponent is allowed by C++17 20.19.3.(7.1)
+      ++p;
+    }
+    if ((p == pend) || !is_integer(*p)) {
+      if(!(fmt & chars_format::fixed)) {
+        // We are in error.
+        return answer;
+      }
+      // Otherwise, we will be ignoring the 'e'.
+      p = location_of_e;
+    } else {
+      while ((p != pend) && is_integer(*p)) {
+        uint8_t digit = uint8_t(*p - '0');
+        if (exp_number < 0x10000000) {
+          exp_number = 10 * exp_number + digit;
+        }
+        ++p;
+      }
+      if(neg_exp) { exp_number = - exp_number; }
+      exponent += exp_number;
+    }
+  } else {
+    // If it scientific and not fixed, we have to bail out.
+    if((fmt & chars_format::scientific) && !(fmt & chars_format::fixed)) { return answer; }
+  }
+  answer.lastmatch = p;
+  answer.valid = true;
+
+  // If we frequently had to deal with long strings of digits,
+  // we could extend our code by using a 128-bit integer instead
+  // of a 64-bit integer. However, this is uncommon.
+  //
+  // We can deal with up to 19 digits.
+  if (digit_count > 19) { // this is uncommon
+    // It is possible that the integer had an overflow.
+    // We have to handle the case where we have 0.0000somenumber.
+    // We need to be mindful of the case where we only have zeroes...
+    // E.g., 0.000000000...000.
+    const char *start = start_digits;
+    while ((start != pend) && (*start == '0' || *start == decimal_point)) {
+      if(*start == '0') { digit_count --; }
+      start++;
+    }
+    if (digit_count > 19) {
+      answer.too_many_digits = true;
+      // Let us start again, this time, avoiding overflows.
+      // We don't need to check if is_integer, since we use the
+      // pre-tokenized spans from above.
+      i = 0;
+      p = answer.integer.ptr;
+      const char* int_end = p + answer.integer.len();
+      const uint64_t minimal_nineteen_digit_integer{1000000000000000000};
+      while((i < minimal_nineteen_digit_integer) && (p != int_end)) {
+        i = i * 10 + uint64_t(*p - '0');
+        ++p;
+      }
+      if (i >= minimal_nineteen_digit_integer) { // We have a big integers
+        exponent = end_of_integer_part - p + exp_number;
+      } else { // We have a value with a fractional component.
+          p = answer.fraction.ptr;
+          const char* frac_end = p + answer.fraction.len();
+          while((i < minimal_nineteen_digit_integer) && (p != frac_end)) {
+            i = i * 10 + uint64_t(*p - '0');
+            ++p;
+          }
+          exponent = answer.fraction.ptr - p + exp_number;
+      }
+      // We have now corrected both exponent and i, to a truncated value
+    }
+  }
+  answer.exponent = exponent;
+  answer.mantissa = i;
+  return answer;
+}
+
+} // namespace fast_float
+
+#endif
diff --git a/libstdc++-v3/src/c++17/fast_float/bigint.h b/libstdc++-v3/src/c++17/fast_float/bigint.h
new file mode 100644
index 00000000000..b56cb9b03b3
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/bigint.h
@@ -0,0 +1,590 @@
+#ifndef FASTFLOAT_BIGINT_H
+#define FASTFLOAT_BIGINT_H
+
+#include <algorithm>
+#include <cstdint>
+#include <climits>
+#include <cstring>
+
+#include "float_common.h"
+
+namespace fast_float {
+
+// the limb width: we want efficient multiplication of double the bits in
+// limb, or for 64-bit limbs, at least 64-bit multiplication where we can
+// extract the high and low parts efficiently. this is every 64-bit
+// architecture except for sparc, which emulates 128-bit multiplication.
+// we might have platforms where `CHAR_BIT` is not 8, so let's avoid
+// doing `8 * sizeof(limb)`.
+#if defined(FASTFLOAT_64BIT) && !defined(__sparc)
+#define FASTFLOAT_64BIT_LIMB
+typedef uint64_t limb;
+constexpr size_t limb_bits = 64;
+#else
+#define FASTFLOAT_32BIT_LIMB
+typedef uint32_t limb;
+constexpr size_t limb_bits = 32;
+#endif
+
+typedef span<limb> limb_span;
+
+// number of bits in a bigint. this needs to be at least the number
+// of bits required to store the largest bigint, which is
+// `log2(10**(digits + max_exp))`, or `log2(10**(767 + 342))`, or
+// ~3600 bits, so we round to 4000.
+constexpr size_t bigint_bits = 4000;
+constexpr size_t bigint_limbs = bigint_bits / limb_bits;
+
+// vector-like type that is allocated on the stack. the entire
+// buffer is pre-allocated, and only the length changes.
+template <uint16_t size>
+struct stackvec {
+  limb data[size];
+  // we never need more than 150 limbs
+  uint16_t length{0};
+
+  stackvec() = default;
+  stackvec(const stackvec &) = delete;
+  stackvec &operator=(const stackvec &) = delete;
+  stackvec(stackvec &&) = delete;
+  stackvec &operator=(stackvec &&other) = delete;
+
+  // create stack vector from existing limb span.
+  stackvec(limb_span s) {
+    FASTFLOAT_ASSERT(try_extend(s));
+  }
+
+  limb& operator[](size_t index) noexcept {
+    FASTFLOAT_DEBUG_ASSERT(index < length);
+    return data[index];
+  }
+  const limb& operator[](size_t index) const noexcept {
+    FASTFLOAT_DEBUG_ASSERT(index < length);
+    return data[index];
+  }
+  // index from the end of the container
+  const limb& rindex(size_t index) const noexcept {
+    FASTFLOAT_DEBUG_ASSERT(index < length);
+    size_t rindex = length - index - 1;
+    return data[rindex];
+  }
+
+  // set the length, without bounds checking.
+  void set_len(size_t len) noexcept {
+    length = uint16_t(len);
+  }
+  constexpr size_t len() const noexcept {
+    return length;
+  }
+  constexpr bool is_empty() const noexcept {
+    return length == 0;
+  }
+  constexpr size_t capacity() const noexcept {
+    return size;
+  }
+  // append item to vector, without bounds checking
+  void push_unchecked(limb value) noexcept {
+    data[length] = value;
+    length++;
+  }
+  // append item to vector, returning if item was added
+  bool try_push(limb value) noexcept {
+    if (len() < capacity()) {
+      push_unchecked(value);
+      return true;
+    } else {
+      return false;
+    }
+  }
+  // add items to the vector, from a span, without bounds checking
+  void extend_unchecked(limb_span s) noexcept {
+    limb* ptr = data + length;
+    ::memcpy((void*)ptr, (const void*)s.ptr, sizeof(limb) * s.len());
+    set_len(len() + s.len());
+  }
+  // try to add items to the vector, returning if items were added
+  bool try_extend(limb_span s) noexcept {
+    if (len() + s.len() <= capacity()) {
+      extend_unchecked(s);
+      return true;
+    } else {
+      return false;
+    }
+  }
+  // resize the vector, without bounds checking
+  // if the new size is longer than the vector, assign value to each
+  // appended item.
+  void resize_unchecked(size_t new_len, limb value) noexcept {
+    if (new_len > len()) {
+      size_t count = new_len - len();
+      limb* first = data + len();
+      limb* last = first + count;
+      ::std::fill(first, last, value);
+      set_len(new_len);
+    } else {
+      set_len(new_len);
+    }
+  }
+  // try to resize the vector, returning if the vector was resized.
+  bool try_resize(size_t new_len, limb value) noexcept {
+    if (new_len > capacity()) {
+      return false;
+    } else {
+      resize_unchecked(new_len, value);
+      return true;
+    }
+  }
+  // check if any limbs are non-zero after the given index.
+  // this needs to be done in reverse order, since the index
+  // is relative to the most significant limbs.
+  bool nonzero(size_t index) const noexcept {
+    while (index < len()) {
+      if (rindex(index) != 0) {
+        return true;
+      }
+      index++;
+    }
+    return false;
+  }
+  // normalize the big integer, so most-significant zero limbs are removed.
+  void normalize() noexcept {
+    while (len() > 0 && rindex(0) == 0) {
+      length--;
+    }
+  }
+};
+
+fastfloat_really_inline
+uint64_t empty_hi64(bool& truncated) noexcept {
+  truncated = false;
+  return 0;
+}
+
+fastfloat_really_inline
+uint64_t uint64_hi64(uint64_t r0, bool& truncated) noexcept {
+  truncated = false;
+  int shl = leading_zeroes(r0);
+  return r0 << shl;
+}
+
+fastfloat_really_inline
+uint64_t uint64_hi64(uint64_t r0, uint64_t r1, bool& truncated) noexcept {
+  int shl = leading_zeroes(r0);
+  if (shl == 0) {
+    truncated = r1 != 0;
+    return r0;
+  } else {
+    int shr = 64 - shl;
+    truncated = (r1 << shl) != 0;
+    return (r0 << shl) | (r1 >> shr);
+  }
+}
+
+fastfloat_really_inline
+uint64_t uint32_hi64(uint32_t r0, bool& truncated) noexcept {
+  return uint64_hi64(r0, truncated);
+}
+
+fastfloat_really_inline
+uint64_t uint32_hi64(uint32_t r0, uint32_t r1, bool& truncated) noexcept {
+  uint64_t x0 = r0;
+  uint64_t x1 = r1;
+  return uint64_hi64((x0 << 32) | x1, truncated);
+}
+
+fastfloat_really_inline
+uint64_t uint32_hi64(uint32_t r0, uint32_t r1, uint32_t r2, bool& truncated) noexcept {
+  uint64_t x0 = r0;
+  uint64_t x1 = r1;
+  uint64_t x2 = r2;
+  return uint64_hi64(x0, (x1 << 32) | x2, truncated);
+}
+
+// add two small integers, checking for overflow.
+// we want an efficient operation. for msvc, where
+// we don't have built-in intrinsics, this is still
+// pretty fast.
+fastfloat_really_inline
+limb scalar_add(limb x, limb y, bool& overflow) noexcept {
+  limb z;
+
+// gcc and clang
+#if defined(__has_builtin)
+  #if __has_builtin(__builtin_add_overflow)
+    overflow = __builtin_add_overflow(x, y, &z);
+    return z;
+  #endif
+#endif
+
+  // generic, this still optimizes correctly on MSVC.
+  z = x + y;
+  overflow = z < x;
+  return z;
+}
+
+// multiply two small integers, getting both the high and low bits.
+fastfloat_really_inline
+limb scalar_mul(limb x, limb y, limb& carry) noexcept {
+#ifdef FASTFLOAT_64BIT_LIMB
+  #if defined(__SIZEOF_INT128__)
+  // GCC and clang both define it as an extension.
+  __uint128_t z = __uint128_t(x) * __uint128_t(y) + __uint128_t(carry);
+  carry = limb(z >> limb_bits);
+  return limb(z);
+  #else
+  // fallback, no native 128-bit integer multiplication with carry.
+  // on msvc, this optimizes identically, somehow.
+  value128 z = full_multiplication(x, y);
+  bool overflow;
+  z.low = scalar_add(z.low, carry, overflow);
+  z.high += uint64_t(overflow);  // cannot overflow
+  carry = z.high;
+  return z.low;
+  #endif
+#else
+  uint64_t z = uint64_t(x) * uint64_t(y) + uint64_t(carry);
+  carry = limb(z >> limb_bits);
+  return limb(z);
+#endif
+}
+
+// add scalar value to bigint starting from offset.
+// used in grade school multiplication
+template <uint16_t size>
+inline bool small_add_from(stackvec<size>& vec, limb y, size_t start) noexcept {
+  size_t index = start;
+  limb carry = y;
+  bool overflow;
+  while (carry != 0 && index < vec.len()) {
+    vec[index] = scalar_add(vec[index], carry, overflow);
+    carry = limb(overflow);
+    index += 1;
+  }
+  if (carry != 0) {
+    FASTFLOAT_TRY(vec.try_push(carry));
+  }
+  return true;
+}
+
+// add scalar value to bigint.
+template <uint16_t size>
+fastfloat_really_inline bool small_add(stackvec<size>& vec, limb y) noexcept {
+  return small_add_from(vec, y, 0);
+}
+
+// multiply bigint by scalar value.
+template <uint16_t size>
+inline bool small_mul(stackvec<size>& vec, limb y) noexcept {
+  limb carry = 0;
+  for (size_t index = 0; index < vec.len(); index++) {
+    vec[index] = scalar_mul(vec[index], y, carry);
+  }
+  if (carry != 0) {
+    FASTFLOAT_TRY(vec.try_push(carry));
+  }
+  return true;
+}
+
+// add bigint to bigint starting from index.
+// used in grade school multiplication
+template <uint16_t size>
+bool large_add_from(stackvec<size>& x, limb_span y, size_t start) noexcept {
+  // the effective x buffer is from `xstart..x.len()`, so exit early
+  // if we can't get that current range.
+  if (x.len() < start || y.len() > x.len() - start) {
+      FASTFLOAT_TRY(x.try_resize(y.len() + start, 0));
+  }
+
+  bool carry = false;
+  for (size_t index = 0; index < y.len(); index++) {
+    limb xi = x[index + start];
+    limb yi = y[index];
+    bool c1 = false;
+    bool c2 = false;
+    xi = scalar_add(xi, yi, c1);
+    if (carry) {
+      xi = scalar_add(xi, 1, c2);
+    }
+    x[index + start] = xi;
+    carry = c1 | c2;
+  }
+
+  // handle overflow
+  if (carry) {
+    FASTFLOAT_TRY(small_add_from(x, 1, y.len() + start));
+  }
+  return true;
+}
+
+// add bigint to bigint.
+template <uint16_t size>
+fastfloat_really_inline bool large_add_from(stackvec<size>& x, limb_span y) noexcept {
+  return large_add_from(x, y, 0);
+}
+
+// grade-school multiplication algorithm
+template <uint16_t size>
+bool long_mul(stackvec<size>& x, limb_span y) noexcept {
+  limb_span xs = limb_span(x.data, x.len());
+  stackvec<size> z(xs);
+  limb_span zs = limb_span(z.data, z.len());
+
+  if (y.len() != 0) {
+    limb y0 = y[0];
+    FASTFLOAT_TRY(small_mul(x, y0));
+    for (size_t index = 1; index < y.len(); index++) {
+      limb yi = y[index];
+      stackvec<size> zi;
+      if (yi != 0) {
+        // re-use the same buffer throughout
+        zi.set_len(0);
+        FASTFLOAT_TRY(zi.try_extend(zs));
+        FASTFLOAT_TRY(small_mul(zi, yi));
+        limb_span zis = limb_span(zi.data, zi.len());
+        FASTFLOAT_TRY(large_add_from(x, zis, index));
+      }
+    }
+  }
+
+  x.normalize();
+  return true;
+}
+
+// grade-school multiplication algorithm
+template <uint16_t size>
+bool large_mul(stackvec<size>& x, limb_span y) noexcept {
+  if (y.len() == 1) {
+    FASTFLOAT_TRY(small_mul(x, y[0]));
+  } else {
+    FASTFLOAT_TRY(long_mul(x, y));
+  }
+  return true;
+}
+
+// big integer type. implements a small subset of big integer
+// arithmetic, using simple algorithms since asymptotically
+// faster algorithms are slower for a small number of limbs.
+// all operations assume the big-integer is normalized.
+struct bigint {
+  // storage of the limbs, in little-endian order.
+  stackvec<bigint_limbs> vec;
+
+  bigint(): vec() {}
+  bigint(const bigint &) = delete;
+  bigint &operator=(const bigint &) = delete;
+  bigint(bigint &&) = delete;
+  bigint &operator=(bigint &&other) = delete;
+
+  bigint(uint64_t value): vec() {
+#ifdef FASTFLOAT_64BIT_LIMB
+    vec.push_unchecked(value);
+#else
+    vec.push_unchecked(uint32_t(value));
+    vec.push_unchecked(uint32_t(value >> 32));
+#endif
+    vec.normalize();
+  }
+
+  // get the high 64 bits from the vector, and if bits were truncated.
+  // this is to get the significant digits for the float.
+  uint64_t hi64(bool& truncated) const noexcept {
+#ifdef FASTFLOAT_64BIT_LIMB
+    if (vec.len() == 0) {
+      return empty_hi64(truncated);
+    } else if (vec.len() == 1) {
+      return uint64_hi64(vec.rindex(0), truncated);
+    } else {
+      uint64_t result = uint64_hi64(vec.rindex(0), vec.rindex(1), truncated);
+      truncated |= vec.nonzero(2);
+      return result;
+    }
+#else
+    if (vec.len() == 0) {
+      return empty_hi64(truncated);
+    } else if (vec.len() == 1) {
+      return uint32_hi64(vec.rindex(0), truncated);
+    } else if (vec.len() == 2) {
+      return uint32_hi64(vec.rindex(0), vec.rindex(1), truncated);
+    } else {
+      uint64_t result = uint32_hi64(vec.rindex(0), vec.rindex(1), vec.rindex(2), truncated);
+      truncated |= vec.nonzero(3);
+      return result;
+    }
+#endif
+  }
+
+  // compare two big integers, returning the large value.
+  // assumes both are normalized. if the return value is
+  // negative, other is larger, if the return value is
+  // positive, this is larger, otherwise they are equal.
+  // the limbs are stored in little-endian order, so we
+  // must compare the limbs in ever order.
+  int compare(const bigint& other) const noexcept {
+    if (vec.len() > other.vec.len()) {
+      return 1;
+    } else if (vec.len() < other.vec.len()) {
+      return -1;
+    } else {
+      for (size_t index = vec.len(); index > 0; index--) {
+        limb xi = vec[index - 1];
+        limb yi = other.vec[index - 1];
+        if (xi > yi) {
+          return 1;
+        } else if (xi < yi) {
+          return -1;
+        }
+      }
+      return 0;
+    }
+  }
+
+  // shift left each limb n bits, carrying over to the new limb
+  // returns true if we were able to shift all the digits.
+  bool shl_bits(size_t n) noexcept {
+    // Internally, for each item, we shift left by n, and add the previous
+    // right shifted limb-bits.
+    // For example, we transform (for u8) shifted left 2, to:
+    //      b10100100 b01000010
+    //      b10 b10010001 b00001000
+    FASTFLOAT_DEBUG_ASSERT(n != 0);
+    FASTFLOAT_DEBUG_ASSERT(n < sizeof(limb) * 8);
+
+    size_t shl = n;
+    size_t shr = limb_bits - shl;
+    limb prev = 0;
+    for (size_t index = 0; index < vec.len(); index++) {
+      limb xi = vec[index];
+      vec[index] = (xi << shl) | (prev >> shr);
+      prev = xi;
+    }
+
+    limb carry = prev >> shr;
+    if (carry != 0) {
+      return vec.try_push(carry);
+    }
+    return true;
+  }
+
+  // move the limbs left by `n` limbs.
+  bool shl_limbs(size_t n) noexcept {
+    FASTFLOAT_DEBUG_ASSERT(n != 0);
+    if (n + vec.len() > vec.capacity()) {
+      return false;
+    } else if (!vec.is_empty()) {
+      // move limbs
+      limb* dst = vec.data + n;
+      const limb* src = vec.data;
+      ::memmove(dst, src, sizeof(limb) * vec.len());
+      // fill in empty limbs
+      limb* first = vec.data;
+      limb* last = first + n;
+      ::std::fill(first, last, 0);
+      vec.set_len(n + vec.len());
+      return true;
+    } else {
+      return true;
+    }
+  }
+
+  // move the limbs left by `n` bits.
+  bool shl(size_t n) noexcept {
+    size_t rem = n % limb_bits;
+    size_t div = n / limb_bits;
+    if (rem != 0) {
+      FASTFLOAT_TRY(shl_bits(rem));
+    }
+    if (div != 0) {
+      FASTFLOAT_TRY(shl_limbs(div));
+    }
+    return true;
+  }
+
+  // get the number of leading zeros in the bigint.
+  int ctlz() const noexcept {
+    if (vec.is_empty()) {
+      return 0;
+    } else {
+#ifdef FASTFLOAT_64BIT_LIMB
+      return leading_zeroes(vec.rindex(0));
+#else
+      // no use defining a specialized leading_zeroes for a 32-bit type.
+      uint64_t r0 = vec.rindex(0);
+      return leading_zeroes(r0 << 32);
+#endif
+    }
+  }
+
+  // get the number of bits in the bigint.
+  int bit_length() const noexcept {
+    int lz = ctlz();
+    return int(limb_bits * vec.len()) - lz;
+  }
+
+  bool mul(limb y) noexcept {
+    return small_mul(vec, y);
+  }
+
+  bool add(limb y) noexcept {
+    return small_add(vec, y);
+  }
+
+  // multiply as if by 2 raised to a power.
+  bool pow2(uint32_t exp) noexcept {
+    return shl(exp);
+  }
+
+  // multiply as if by 5 raised to a power.
+  bool pow5(uint32_t exp) noexcept {
+    // multiply by a power of 5
+    static constexpr uint32_t large_step = 135;
+    static constexpr uint64_t small_power_of_5[] = {
+      1UL, 5UL, 25UL, 125UL, 625UL, 3125UL, 15625UL, 78125UL, 390625UL,
+      1953125UL, 9765625UL, 48828125UL, 244140625UL, 1220703125UL,
+      6103515625UL, 30517578125UL, 152587890625UL, 762939453125UL,
+      3814697265625UL, 19073486328125UL, 95367431640625UL, 476837158203125UL,
+      2384185791015625UL, 11920928955078125UL, 59604644775390625UL,
+      298023223876953125UL, 1490116119384765625UL, 7450580596923828125UL,
+    };
+#ifdef FASTFLOAT_64BIT_LIMB
+    constexpr static limb large_power_of_5[] = {
+      1414648277510068013UL, 9180637584431281687UL, 4539964771860779200UL,
+      10482974169319127550UL, 198276706040285095UL};
+#else
+    constexpr static limb large_power_of_5[] = {
+      4279965485U, 329373468U, 4020270615U, 2137533757U, 4287402176U,
+      1057042919U, 1071430142U, 2440757623U, 381945767U, 46164893U};
+#endif
+    size_t large_length = sizeof(large_power_of_5) / sizeof(limb);
+    limb_span large = limb_span(large_power_of_5, large_length);
+    while (exp >= large_step) {
+      FASTFLOAT_TRY(large_mul(vec, large));
+      exp -= large_step;
+    }
+#ifdef FASTFLOAT_64BIT_LIMB
+    uint32_t small_step = 27;
+    limb max_native = 7450580596923828125UL;
+#else
+    uint32_t small_step = 13;
+    limb max_native = 1220703125U;
+#endif
+    while (exp >= small_step) {
+      FASTFLOAT_TRY(small_mul(vec, max_native));
+      exp -= small_step;
+    }
+    if (exp != 0) {
+      FASTFLOAT_TRY(small_mul(vec, limb(small_power_of_5[exp])));
+    }
+
+    return true;
+  }
+
+  // multiply as if by 10 raised to a power.
+  bool pow10(uint32_t exp) noexcept {
+    FASTFLOAT_TRY(pow5(exp));
+    return pow2(exp);
+  }
+};
+
+} // namespace fast_float
+
+#endif
diff --git a/libstdc++-v3/src/c++17/fast_float/decimal_to_binary.h b/libstdc++-v3/src/c++17/fast_float/decimal_to_binary.h
new file mode 100644
index 00000000000..6da6c66a3ac
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/decimal_to_binary.h
@@ -0,0 +1,194 @@
+#ifndef FASTFLOAT_DECIMAL_TO_BINARY_H
+#define FASTFLOAT_DECIMAL_TO_BINARY_H
+
+#include "float_common.h"
+#include "fast_table.h"
+#include <cfloat>
+#include <cinttypes>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+
+namespace fast_float {
+
+// This will compute or rather approximate w * 5**q and return a pair of 64-bit words approximating
+// the result, with the "high" part corresponding to the most significant bits and the
+// low part corresponding to the least significant bits.
+//
+template <int bit_precision>
+fastfloat_really_inline
+value128 compute_product_approximation(int64_t q, uint64_t w) {
+  const int index = 2 * int(q - powers::smallest_power_of_five);
+  // For small values of q, e.g., q in [0,27], the answer is always exact because
+  // The line value128 firstproduct = full_multiplication(w, power_of_five_128[index]);
+  // gives the exact answer.
+  value128 firstproduct = full_multiplication(w, powers::power_of_five_128[index]);
+  static_assert((bit_precision >= 0) && (bit_precision <= 64), " precision should  be in (0,64]");
+  constexpr uint64_t precision_mask = (bit_precision < 64) ?
+               (uint64_t(0xFFFFFFFFFFFFFFFF) >> bit_precision)
+               : uint64_t(0xFFFFFFFFFFFFFFFF);
+  if((firstproduct.high & precision_mask) == precision_mask) { // could further guard with  (lower + w < lower)
+    // regarding the second product, we only need secondproduct.high, but our expectation is that the compiler will optimize this extra work away if needed.
+    value128 secondproduct = full_multiplication(w, powers::power_of_five_128[index + 1]);
+    firstproduct.low += secondproduct.high;
+    if(secondproduct.high > firstproduct.low) {
+      firstproduct.high++;
+    }
+  }
+  return firstproduct;
+}
+
+namespace detail {
+/**
+ * For q in (0,350), we have that
+ *  f = (((152170 + 65536) * q ) >> 16);
+ * is equal to
+ *   floor(p) + q
+ * where
+ *   p = log(5**q)/log(2) = q * log(5)/log(2)
+ *
+ * For negative values of q in (-400,0), we have that 
+ *  f = (((152170 + 65536) * q ) >> 16);
+ * is equal to 
+ *   -ceil(p) + q
+ * where
+ *   p = log(5**-q)/log(2) = -q * log(5)/log(2)
+ */
+  constexpr fastfloat_really_inline int32_t power(int32_t q)  noexcept  {
+    return (((152170 + 65536) * q) >> 16) + 63;
+  }
+} // namespace detail
+
+// create an adjusted mantissa, biased by the invalid power2
+// for significant digits already multiplied by 10 ** q.
+template <typename binary>
+fastfloat_really_inline
+adjusted_mantissa compute_error_scaled(int64_t q, uint64_t w, int lz) noexcept  {
+  int hilz = int(w >> 63) ^ 1;
+  adjusted_mantissa answer;
+  answer.mantissa = w << hilz;
+  int bias = binary::mantissa_explicit_bits() - binary::minimum_exponent();
+  answer.power2 = int32_t(detail::power(int32_t(q)) + bias - hilz - lz - 62 + invalid_am_bias);
+  return answer;
+}
+
+// w * 10 ** q, without rounding the representation up.
+// the power2 in the exponent will be adjusted by invalid_am_bias.
+template <typename binary>
+fastfloat_really_inline
+adjusted_mantissa compute_error(int64_t q, uint64_t w)  noexcept  {
+  int lz = leading_zeroes(w);
+  w <<= lz;
+  value128 product = compute_product_approximation<binary::mantissa_explicit_bits() + 3>(q, w);
+  return compute_error_scaled<binary>(q, product.high, lz);
+}
+
+// w * 10 ** q
+// The returned value should be a valid ieee64 number that simply need to be packed.
+// However, in some very rare cases, the computation will fail. In such cases, we
+// return an adjusted_mantissa with a negative power of 2: the caller should recompute
+// in such cases.
+template <typename binary>
+fastfloat_really_inline
+adjusted_mantissa compute_float(int64_t q, uint64_t w)  noexcept  {
+  adjusted_mantissa answer;
+  if ((w == 0) || (q < binary::smallest_power_of_ten())) {
+    answer.power2 = 0;
+    answer.mantissa = 0;
+    // result should be zero
+    return answer;
+  }
+  if (q > binary::largest_power_of_ten()) {
+    // we want to get infinity:
+    answer.power2 = binary::infinite_power();
+    answer.mantissa = 0;
+    return answer;
+  }
+  // At this point in time q is in [powers::smallest_power_of_five, powers::largest_power_of_five].
+
+  // We want the most significant bit of i to be 1. Shift if needed.
+  int lz = leading_zeroes(w);
+  w <<= lz;
+
+  // The required precision is binary::mantissa_explicit_bits() + 3 because
+  // 1. We need the implicit bit
+  // 2. We need an extra bit for rounding purposes
+  // 3. We might lose a bit due to the "upperbit" routine (result too small, requiring a shift)
+
+  value128 product = compute_product_approximation<binary::mantissa_explicit_bits() + 3>(q, w);
+  if(product.low == 0xFFFFFFFFFFFFFFFF) { //  could guard it further
+    // In some very rare cases, this could happen, in which case we might need a more accurate
+    // computation that what we can provide cheaply. This is very, very unlikely.
+    //
+    const bool inside_safe_exponent = (q >= -27) && (q <= 55); // always good because 5**q <2**128 when q>=0, 
+    // and otherwise, for q<0, we have 5**-q<2**64 and the 128-bit reciprocal allows for exact computation.
+    if(!inside_safe_exponent) {
+      return compute_error_scaled<binary>(q, product.high, lz);
+    }
+  }
+  // The "compute_product_approximation" function can be slightly slower than a branchless approach:
+  // value128 product = compute_product(q, w);
+  // but in practice, we can win big with the compute_product_approximation if its additional branch
+  // is easily predicted. Which is best is data specific.
+  int upperbit = int(product.high >> 63);
+
+  answer.mantissa = product.high >> (upperbit + 64 - binary::mantissa_explicit_bits() - 3);
+
+  answer.power2 = int32_t(detail::power(int32_t(q)) + upperbit - lz - binary::minimum_exponent());
+  if (answer.power2 <= 0) { // we have a subnormal?
+    // Here have that answer.power2 <= 0 so -answer.power2 >= 0
+    if(-answer.power2 + 1 >= 64) { // if we have more than 64 bits below the minimum exponent, you have a zero for sure.
+      answer.power2 = 0;
+      answer.mantissa = 0;
+      // result should be zero
+      return answer;
+    }
+    // next line is safe because -answer.power2 + 1 < 64
+    answer.mantissa >>= -answer.power2 + 1;
+    // Thankfully, we can't have both "round-to-even" and subnormals because
+    // "round-to-even" only occurs for powers close to 0.
+    answer.mantissa += (answer.mantissa & 1); // round up
+    answer.mantissa >>= 1;
+    // There is a weird scenario where we don't have a subnormal but just.
+    // Suppose we start with 2.2250738585072013e-308, we end up
+    // with 0x3fffffffffffff x 2^-1023-53 which is technically subnormal
+    // whereas 0x40000000000000 x 2^-1023-53  is normal. Now, we need to round
+    // up 0x3fffffffffffff x 2^-1023-53  and once we do, we are no longer
+    // subnormal, but we can only know this after rounding.
+    // So we only declare a subnormal if we are smaller than the threshold.
+    answer.power2 = (answer.mantissa < (uint64_t(1) << binary::mantissa_explicit_bits())) ? 0 : 1;
+    return answer;
+  }
+
+  // usually, we round *up*, but if we fall right in between and and we have an
+  // even basis, we need to round down
+  // We are only concerned with the cases where 5**q fits in single 64-bit word.
+  if ((product.low <= 1) &&  (q >= binary::min_exponent_round_to_even()) && (q <= binary::max_exponent_round_to_even()) &&
+      ((answer.mantissa & 3) == 1) ) { // we may fall between two floats!
+    // To be in-between two floats we need that in doing
+    //   answer.mantissa = product.high >> (upperbit + 64 - binary::mantissa_explicit_bits() - 3);
+    // ... we dropped out only zeroes. But if this happened, then we can go back!!!
+    if((answer.mantissa  << (upperbit + 64 - binary::mantissa_explicit_bits() - 3)) ==  product.high) {
+      answer.mantissa &= ~uint64_t(1);          // flip it so that we do not round up
+    }
+  }
+
+  answer.mantissa += (answer.mantissa & 1); // round up
+  answer.mantissa >>= 1;
+  if (answer.mantissa >= (uint64_t(2) << binary::mantissa_explicit_bits())) {
+    answer.mantissa = (uint64_t(1) << binary::mantissa_explicit_bits());
+    answer.power2++; // undo previous addition
+  }
+
+  answer.mantissa &= ~(uint64_t(1) << binary::mantissa_explicit_bits());
+  if (answer.power2 >= binary::infinite_power()) { // infinity
+    answer.power2 = binary::infinite_power();
+    answer.mantissa = 0;
+  }
+  return answer;
+}
+
+} // namespace fast_float
+
+#endif
diff --git a/libstdc++-v3/src/c++17/fast_float/digit_comparison.h b/libstdc++-v3/src/c++17/fast_float/digit_comparison.h
new file mode 100644
index 00000000000..7ffe874303b
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/digit_comparison.h
@@ -0,0 +1,423 @@
+#ifndef FASTFLOAT_DIGIT_COMPARISON_H
+#define FASTFLOAT_DIGIT_COMPARISON_H
+
+#include <algorithm>
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+
+#include "float_common.h"
+#include "bigint.h"
+#include "ascii_number.h"
+
+namespace fast_float {
+
+// 1e0 to 1e19
+constexpr static uint64_t powers_of_ten_uint64[] = {
+    1UL, 10UL, 100UL, 1000UL, 10000UL, 100000UL, 1000000UL, 10000000UL, 100000000UL,
+    1000000000UL, 10000000000UL, 100000000000UL, 1000000000000UL, 10000000000000UL,
+    100000000000000UL, 1000000000000000UL, 10000000000000000UL, 100000000000000000UL,
+    1000000000000000000UL, 10000000000000000000UL};
+
+// calculate the exponent, in scientific notation, of the number.
+// this algorithm is not even close to optimized, but it has no practical
+// effect on performance: in order to have a faster algorithm, we'd need
+// to slow down performance for faster algorithms, and this is still fast.
+fastfloat_really_inline int32_t scientific_exponent(parsed_number_string& num) noexcept {
+  uint64_t mantissa = num.mantissa;
+  int32_t exponent = int32_t(num.exponent);
+  while (mantissa >= 10000) {
+    mantissa /= 10000;
+    exponent += 4;
+  }
+  while (mantissa >= 100) {
+    mantissa /= 100;
+    exponent += 2;
+  }
+  while (mantissa >= 10) {
+    mantissa /= 10;
+    exponent += 1;
+  }
+  return exponent;
+}
+
+// this converts a native floating-point number to an extended-precision float.
+template <typename T>
+fastfloat_really_inline adjusted_mantissa to_extended(T value) noexcept {
+  adjusted_mantissa am;
+  int32_t bias = binary_format<T>::mantissa_explicit_bits() - binary_format<T>::minimum_exponent();
+  if (std::is_same<T, float>::value) {
+    constexpr uint32_t exponent_mask = 0x7F800000;
+    constexpr uint32_t mantissa_mask = 0x007FFFFF;
+    constexpr uint64_t hidden_bit_mask = 0x00800000;
+    uint32_t bits;
+    ::memcpy(&bits, &value, sizeof(T));
+    if ((bits & exponent_mask) == 0) {
+      // denormal
+      am.power2 = 1 - bias;
+      am.mantissa = bits & mantissa_mask;
+    } else {
+      // normal
+      am.power2 = int32_t((bits & exponent_mask) >> binary_format<T>::mantissa_explicit_bits());
+      am.power2 -= bias;
+      am.mantissa = (bits & mantissa_mask) | hidden_bit_mask;
+    }
+  } else {
+    constexpr uint64_t exponent_mask = 0x7FF0000000000000;
+    constexpr uint64_t mantissa_mask = 0x000FFFFFFFFFFFFF;
+    constexpr uint64_t hidden_bit_mask = 0x0010000000000000;
+    uint64_t bits;
+    ::memcpy(&bits, &value, sizeof(T));
+    if ((bits & exponent_mask) == 0) {
+      // denormal
+      am.power2 = 1 - bias;
+      am.mantissa = bits & mantissa_mask;
+    } else {
+      // normal
+      am.power2 = int32_t((bits & exponent_mask) >> binary_format<T>::mantissa_explicit_bits());
+      am.power2 -= bias;
+      am.mantissa = (bits & mantissa_mask) | hidden_bit_mask;
+    }
+  }
+
+  return am;
+}
+
+// get the extended precision value of the halfway point between b and b+u.
+// we are given a native float that represents b, so we need to adjust it
+// halfway between b and b+u.
+template <typename T>
+fastfloat_really_inline adjusted_mantissa to_extended_halfway(T value) noexcept {
+  adjusted_mantissa am = to_extended(value);
+  am.mantissa <<= 1;
+  am.mantissa += 1;
+  am.power2 -= 1;
+  return am;
+}
+
+// round an extended-precision float to the nearest machine float.
+template <typename T, typename callback>
+fastfloat_really_inline void round(adjusted_mantissa& am, callback cb) noexcept {
+  int32_t mantissa_shift = 64 - binary_format<T>::mantissa_explicit_bits() - 1;
+  if (-am.power2 >= mantissa_shift) {
+    // have a denormal float
+    int32_t shift = -am.power2 + 1;
+    cb(am, std::min(shift, 64));
+    // check for round-up: if rounding-nearest carried us to the hidden bit.
+    am.power2 = (am.mantissa < (uint64_t(1) << binary_format<T>::mantissa_explicit_bits())) ? 0 : 1;
+    return;
+  }
+
+  // have a normal float, use the default shift.
+  cb(am, mantissa_shift);
+
+  // check for carry
+  if (am.mantissa >= (uint64_t(2) << binary_format<T>::mantissa_explicit_bits())) {
+    am.mantissa = (uint64_t(1) << binary_format<T>::mantissa_explicit_bits());
+    am.power2++;
+  }
+
+  // check for infinite: we could have carried to an infinite power
+  am.mantissa &= ~(uint64_t(1) << binary_format<T>::mantissa_explicit_bits());
+  if (am.power2 >= binary_format<T>::infinite_power()) {
+    am.power2 = binary_format<T>::infinite_power();
+    am.mantissa = 0;
+  }
+}
+
+template <typename callback>
+fastfloat_really_inline
+void round_nearest_tie_even(adjusted_mantissa& am, int32_t shift, callback cb) noexcept {
+  uint64_t mask;
+  uint64_t halfway;
+  if (shift == 64) {
+    mask = UINT64_MAX;
+  } else {
+    mask = (uint64_t(1) << shift) - 1;
+  }
+  if (shift == 0) {
+    halfway = 0;
+  } else {
+    halfway = uint64_t(1) << (shift - 1);
+  }
+  uint64_t truncated_bits = am.mantissa & mask;
+  uint64_t is_above = truncated_bits > halfway;
+  uint64_t is_halfway = truncated_bits == halfway;
+
+  // shift digits into position
+  if (shift == 64) {
+    am.mantissa = 0;
+  } else {
+    am.mantissa >>= shift;
+  }
+  am.power2 += shift;
+
+  bool is_odd = (am.mantissa & 1) == 1;
+  am.mantissa += uint64_t(cb(is_odd, is_halfway, is_above));
+}
+
+fastfloat_really_inline void round_down(adjusted_mantissa& am, int32_t shift) noexcept {
+  if (shift == 64) {
+    am.mantissa = 0;
+  } else {
+    am.mantissa >>= shift;
+  }
+  am.power2 += shift;
+}
+
+fastfloat_really_inline void skip_zeros(const char*& first, const char* last) noexcept {
+  uint64_t val;
+  while (std::distance(first, last) >= 8) {
+    ::memcpy(&val, first, sizeof(uint64_t));
+    if (val != 0x3030303030303030) {
+      break;
+    }
+    first += 8;
+  }
+  while (first != last) {
+    if (*first != '0') {
+      break;
+    }
+    first++;
+  }
+}
+
+// determine if any non-zero digits were truncated.
+// all characters must be valid digits.
+fastfloat_really_inline bool is_truncated(const char* first, const char* last) noexcept {
+  // do 8-bit optimizations, can just compare to 8 literal 0s.
+  uint64_t val;
+  while (std::distance(first, last) >= 8) {
+    ::memcpy(&val, first, sizeof(uint64_t));
+    if (val != 0x3030303030303030) {
+      return true;
+    }
+    first += 8;
+  }
+  while (first != last) {
+    if (*first != '0') {
+      return true;
+    }
+    first++;
+  }
+  return false;
+}
+
+fastfloat_really_inline bool is_truncated(byte_span s) noexcept {
+  return is_truncated(s.ptr, s.ptr + s.len());
+}
+
+fastfloat_really_inline
+void parse_eight_digits(const char*& p, limb& value, size_t& counter, size_t& count) noexcept {
+  value = value * 100000000 + parse_eight_digits_unrolled(p);
+  p += 8;
+  counter += 8;
+  count += 8;
+}
+
+fastfloat_really_inline
+void parse_one_digit(const char*& p, limb& value, size_t& counter, size_t& count) noexcept {
+  value = value * 10 + limb(*p - '0');
+  p++;
+  counter++;
+  count++;
+}
+
+fastfloat_really_inline
+void add_native(bigint& big, limb power, limb value) noexcept {
+  big.mul(power);
+  big.add(value);
+}
+
+fastfloat_really_inline void round_up_bigint(bigint& big, size_t& count) noexcept {
+  // need to round-up the digits, but need to avoid rounding
+  // ....9999 to ...10000, which could cause a false halfway point.
+  add_native(big, 10, 1);
+  count++;
+}
+
+// parse the significant digits into a big integer
+inline void parse_mantissa(bigint& result, parsed_number_string& num, size_t max_digits, size_t& digits) noexcept {
+  // try to minimize the number of big integer and scalar multiplication.
+  // therefore, try to parse 8 digits at a time, and multiply by the largest
+  // scalar value (9 or 19 digits) for each step.
+  size_t counter = 0;
+  digits = 0;
+  limb value = 0;
+#ifdef FASTFLOAT_64BIT_LIMB
+  size_t step = 19;
+#else
+  size_t step = 9;
+#endif
+
+  // process all integer digits.
+  const char* p = num.integer.ptr;
+  const char* pend = p + num.integer.len();
+  skip_zeros(p, pend);
+  // process all digits, in increments of step per loop
+  while (p != pend) {
+    while ((std::distance(p, pend) >= 8) && (step - counter >= 8) && (max_digits - digits >= 8)) {
+      parse_eight_digits(p, value, counter, digits);
+    }
+    while (counter < step && p != pend && digits < max_digits) {
+      parse_one_digit(p, value, counter, digits);
+    }
+    if (digits == max_digits) {
+      // add the temporary value, then check if we've truncated any digits
+      add_native(result, limb(powers_of_ten_uint64[counter]), value);
+      bool truncated = is_truncated(p, pend);
+      if (num.fraction.ptr != nullptr) {
+        truncated |= is_truncated(num.fraction);
+      }
+      if (truncated) {
+        round_up_bigint(result, digits);
+      }
+      return;
+    } else {
+      add_native(result, limb(powers_of_ten_uint64[counter]), value);
+      counter = 0;
+      value = 0;
+    }
+  }
+
+  // add our fraction digits, if they're available.
+  if (num.fraction.ptr != nullptr) {
+    p = num.fraction.ptr;
+    pend = p + num.fraction.len();
+    if (digits == 0) {
+      skip_zeros(p, pend);
+    }
+    // process all digits, in increments of step per loop
+    while (p != pend) {
+      while ((std::distance(p, pend) >= 8) && (step - counter >= 8) && (max_digits - digits >= 8)) {
+        parse_eight_digits(p, value, counter, digits);
+      }
+      while (counter < step && p != pend && digits < max_digits) {
+        parse_one_digit(p, value, counter, digits);
+      }
+      if (digits == max_digits) {
+        // add the temporary value, then check if we've truncated any digits
+        add_native(result, limb(powers_of_ten_uint64[counter]), value);
+        bool truncated = is_truncated(p, pend);
+        if (truncated) {
+          round_up_bigint(result, digits);
+        }
+        return;
+      } else {
+        add_native(result, limb(powers_of_ten_uint64[counter]), value);
+        counter = 0;
+        value = 0;
+      }
+    }
+  }
+
+  if (counter != 0) {
+    add_native(result, limb(powers_of_ten_uint64[counter]), value);
+  }
+}
+
+template <typename T>
+inline adjusted_mantissa positive_digit_comp(bigint& bigmant, int32_t exponent) noexcept {
+  FASTFLOAT_ASSERT(bigmant.pow10(uint32_t(exponent)));
+  adjusted_mantissa answer;
+  bool truncated;
+  answer.mantissa = bigmant.hi64(truncated);
+  int bias = binary_format<T>::mantissa_explicit_bits() - binary_format<T>::minimum_exponent();
+  answer.power2 = bigmant.bit_length() - 64 + bias;
+
+  round<T>(answer, [truncated](adjusted_mantissa& a, int32_t shift) {
+    round_nearest_tie_even(a, shift, [truncated](bool is_odd, bool is_halfway, bool is_above) -> bool {
+      return is_above || (is_halfway && truncated) || (is_odd && is_halfway);
+    });
+  });
+
+  return answer;
+}
+
+// the scaling here is quite simple: we have, for the real digits `m * 10^e`,
+// and for the theoretical digits `n * 2^f`. Since `e` is always negative,
+// to scale them identically, we do `n * 2^f * 5^-f`, so we now have `m * 2^e`.
+// we then need to scale by `2^(f- e)`, and then the two significant digits
+// are of the same magnitude.
+template <typename T>
+inline adjusted_mantissa negative_digit_comp(bigint& bigmant, adjusted_mantissa am, int32_t exponent) noexcept {
+  bigint& real_digits = bigmant;
+  int32_t real_exp = exponent;
+
+  // get the value of `b`, rounded down, and get a bigint representation of b+h
+  adjusted_mantissa am_b = am;
+  // gcc7 buf: use a lambda to remove the noexcept qualifier bug with -Wnoexcept-type.
+  round<T>(am_b, [](adjusted_mantissa&a, int32_t shift) { round_down(a, shift); });
+  T b;
+  to_float(false, am_b, b);
+  adjusted_mantissa theor = to_extended_halfway(b);
+  bigint theor_digits(theor.mantissa);
+  int32_t theor_exp = theor.power2;
+
+  // scale real digits and theor digits to be same power.
+  int32_t pow2_exp = theor_exp - real_exp;
+  uint32_t pow5_exp = uint32_t(-real_exp);
+  if (pow5_exp != 0) {
+    FASTFLOAT_ASSERT(theor_digits.pow5(pow5_exp));
+  }
+  if (pow2_exp > 0) {
+    FASTFLOAT_ASSERT(theor_digits.pow2(uint32_t(pow2_exp)));
+  } else if (pow2_exp < 0) {
+    FASTFLOAT_ASSERT(real_digits.pow2(uint32_t(-pow2_exp)));
+  }
+
+  // compare digits, and use it to director rounding
+  int ord = real_digits.compare(theor_digits);
+  adjusted_mantissa answer = am;
+  round<T>(answer, [ord](adjusted_mantissa& a, int32_t shift) {
+    round_nearest_tie_even(a, shift, [ord](bool is_odd, bool _, bool __) -> bool {
+      (void)_;  // not needed, since we've done our comparison
+      (void)__; // not needed, since we've done our comparison
+      if (ord > 0) {
+        return true;
+      } else if (ord < 0) {
+        return false;
+      } else {
+        return is_odd;
+      }
+    });
+  });
+
+  return answer;
+}
+
+// parse the significant digits as a big integer to unambiguously round the
+// the significant digits. here, we are trying to determine how to round
+// an extended float representation close to `b+h`, halfway between `b`
+// (the float rounded-down) and `b+u`, the next positive float. this
+// algorithm is always correct, and uses one of two approaches. when
+// the exponent is positive relative to the significant digits (such as
+// 1234), we create a big-integer representation, get the high 64-bits,
+// determine if any lower bits are truncated, and use that to direct
+// rounding. in case of a negative exponent relative to the significant
+// digits (such as 1.2345), we create a theoretical representation of
+// `b` as a big-integer type, scaled to the same binary exponent as
+// the actual digits. we then compare the big integer representations
+// of both, and use that to direct rounding.
+template <typename T>
+inline adjusted_mantissa digit_comp(parsed_number_string& num, adjusted_mantissa am) noexcept {
+  // remove the invalid exponent bias
+  am.power2 -= invalid_am_bias;
+
+  int32_t sci_exp = scientific_exponent(num);
+  size_t max_digits = binary_format<T>::max_digits();
+  size_t digits = 0;
+  bigint bigmant;
+  parse_mantissa(bigmant, num, max_digits, digits);
+  // can't underflow, since digits is at most max_digits.
+  int32_t exponent = sci_exp + 1 - int32_t(digits);
+  if (exponent >= 0) {
+    return positive_digit_comp<T>(bigmant, exponent);
+  } else {
+    return negative_digit_comp<T>(bigmant, am, exponent);
+  }
+}
+
+} // namespace fast_float
+
+#endif
diff --git a/libstdc++-v3/src/c++17/fast_float/fast_float.h b/libstdc++-v3/src/c++17/fast_float/fast_float.h
new file mode 100644
index 00000000000..3c483803af3
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/fast_float.h
@@ -0,0 +1,63 @@
+#ifndef FASTFLOAT_FAST_FLOAT_H
+#define FASTFLOAT_FAST_FLOAT_H
+
+#include <system_error>
+
+namespace fast_float {
+enum chars_format {
+    scientific = 1<<0,
+    fixed = 1<<2,
+    hex = 1<<3,
+    general = fixed | scientific
+};
+
+
+struct from_chars_result {
+  const char *ptr;
+  std::errc ec;
+};
+
+struct parse_options {
+  constexpr explicit parse_options(chars_format fmt = chars_format::general,
+                         char dot = '.')
+    : format(fmt), decimal_point(dot) {}
+
+  /** Which number formats are accepted */
+  chars_format format;
+  /** The character used as decimal point */
+  char decimal_point;
+};
+
+/**
+ * This function parses the character sequence [first,last) for a number. It parses floating-point numbers expecting
+ * a locale-indepent format equivalent to what is used by std::strtod in the default ("C") locale.
+ * The resulting floating-point value is the closest floating-point values (using either float or double),
+ * using the "round to even" convention for values that would otherwise fall right in-between two values.
+ * That is, we provide exact parsing according to the IEEE standard.
+ *
+ * Given a successful parse, the pointer (`ptr`) in the returned value is set to point right after the
+ * parsed number, and the `value` referenced is set to the parsed value. In case of error, the returned
+ * `ec` contains a representative error, otherwise the default (`std::errc()`) value is stored.
+ *
+ * The implementation does not throw and does not allocate memory (e.g., with `new` or `malloc`).
+ *
+ * Like the C++17 standard, the `fast_float::from_chars` functions take an optional last argument of
+ * the type `fast_float::chars_format`. It is a bitset value: we check whether
+ * `fmt & fast_float::chars_format::fixed` and `fmt & fast_float::chars_format::scientific` are set
+ * to determine whether we allowe the fixed point and scientific notation respectively.
+ * The default is  `fast_float::chars_format::general` which allows both `fixed` and `scientific`.
+ */
+template<typename T>
+from_chars_result from_chars(const char *first, const char *last,
+                             T &value, chars_format fmt = chars_format::general)  noexcept;
+
+/**
+ * Like from_chars, but accepts an `options` argument to govern number parsing.
+ */
+template<typename T>
+from_chars_result from_chars_advanced(const char *first, const char *last,
+                                      T &value, parse_options options)  noexcept;
+
+}
+#include "parse_number.h"
+#endif // FASTFLOAT_FAST_FLOAT_H
diff --git a/libstdc++-v3/src/c++17/fast_float/fast_table.h b/libstdc++-v3/src/c++17/fast_float/fast_table.h
new file mode 100644
index 00000000000..5766274ca41
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/fast_table.h
@@ -0,0 +1,699 @@
+#ifndef FASTFLOAT_FAST_TABLE_H
+#define FASTFLOAT_FAST_TABLE_H
+
+#include <cstdint>
+
+namespace fast_float {
+
+/**
+ * When mapping numbers from decimal to binary,
+ * we go from w * 10^q to m * 2^p but we have
+ * 10^q = 5^q * 2^q, so effectively
+ * we are trying to match
+ * w * 2^q * 5^q to m * 2^p. Thus the powers of two
+ * are not a concern since they can be represented
+ * exactly using the binary notation, only the powers of five
+ * affect the binary significand.
+ */
+
+/**
+ * The smallest non-zero float (binary64) is 2^−1074.
+ * We take as input numbers of the form w x 10^q where w < 2^64.
+ * We have that w * 10^-343  <  2^(64-344) 5^-343 < 2^-1076.
+ * However, we have that
+ * (2^64-1) * 10^-342 =  (2^64-1) * 2^-342 * 5^-342 > 2^−1074.
+ * Thus it is possible for a number of the form w * 10^-342 where
+ * w is a 64-bit value to be a non-zero floating-point number.
+ *********
+ * Any number of form w * 10^309 where w>= 1 is going to be
+ * infinite in binary64 so we never need to worry about powers
+ * of 5 greater than 308.
+ */
+template <class unused = void>
+struct powers_template {
+
+constexpr static int smallest_power_of_five = binary_format<double>::smallest_power_of_ten();
+constexpr static int largest_power_of_five = binary_format<double>::largest_power_of_ten();
+constexpr static int number_of_entries = 2 * (largest_power_of_five - smallest_power_of_five + 1);
+// Powers of five from 5^-342 all the way to 5^308 rounded toward one.
+static const uint64_t power_of_five_128[number_of_entries];
+};
+
+template <class unused>
+const uint64_t powers_template<unused>::power_of_five_128[number_of_entries] = {
+        0xeef453d6923bd65a,0x113faa2906a13b3f,
+        0x9558b4661b6565f8,0x4ac7ca59a424c507,
+        0xbaaee17fa23ebf76,0x5d79bcf00d2df649,
+        0xe95a99df8ace6f53,0xf4d82c2c107973dc,
+        0x91d8a02bb6c10594,0x79071b9b8a4be869,
+        0xb64ec836a47146f9,0x9748e2826cdee284,
+        0xe3e27a444d8d98b7,0xfd1b1b2308169b25,
+        0x8e6d8c6ab0787f72,0xfe30f0f5e50e20f7,
+        0xb208ef855c969f4f,0xbdbd2d335e51a935,
+        0xde8b2b66b3bc4723,0xad2c788035e61382,
+        0x8b16fb203055ac76,0x4c3bcb5021afcc31,
+        0xaddcb9e83c6b1793,0xdf4abe242a1bbf3d,
+        0xd953e8624b85dd78,0xd71d6dad34a2af0d,
+        0x87d4713d6f33aa6b,0x8672648c40e5ad68,
+        0xa9c98d8ccb009506,0x680efdaf511f18c2,
+        0xd43bf0effdc0ba48,0x212bd1b2566def2,
+        0x84a57695fe98746d,0x14bb630f7604b57,
+        0xa5ced43b7e3e9188,0x419ea3bd35385e2d,
+        0xcf42894a5dce35ea,0x52064cac828675b9,
+        0x818995ce7aa0e1b2,0x7343efebd1940993,
+        0xa1ebfb4219491a1f,0x1014ebe6c5f90bf8,
+        0xca66fa129f9b60a6,0xd41a26e077774ef6,
+        0xfd00b897478238d0,0x8920b098955522b4,
+        0x9e20735e8cb16382,0x55b46e5f5d5535b0,
+        0xc5a890362fddbc62,0xeb2189f734aa831d,
+        0xf712b443bbd52b7b,0xa5e9ec7501d523e4,
+        0x9a6bb0aa55653b2d,0x47b233c92125366e,
+        0xc1069cd4eabe89f8,0x999ec0bb696e840a,
+        0xf148440a256e2c76,0xc00670ea43ca250d,
+        0x96cd2a865764dbca,0x380406926a5e5728,
+        0xbc807527ed3e12bc,0xc605083704f5ecf2,
+        0xeba09271e88d976b,0xf7864a44c633682e,
+        0x93445b8731587ea3,0x7ab3ee6afbe0211d,
+        0xb8157268fdae9e4c,0x5960ea05bad82964,
+        0xe61acf033d1a45df,0x6fb92487298e33bd,
+        0x8fd0c16206306bab,0xa5d3b6d479f8e056,
+        0xb3c4f1ba87bc8696,0x8f48a4899877186c,
+        0xe0b62e2929aba83c,0x331acdabfe94de87,
+        0x8c71dcd9ba0b4925,0x9ff0c08b7f1d0b14,
+        0xaf8e5410288e1b6f,0x7ecf0ae5ee44dd9,
+        0xdb71e91432b1a24a,0xc9e82cd9f69d6150,
+        0x892731ac9faf056e,0xbe311c083a225cd2,
+        0xab70fe17c79ac6ca,0x6dbd630a48aaf406,
+        0xd64d3d9db981787d,0x92cbbccdad5b108,
+        0x85f0468293f0eb4e,0x25bbf56008c58ea5,
+        0xa76c582338ed2621,0xaf2af2b80af6f24e,
+        0xd1476e2c07286faa,0x1af5af660db4aee1,
+        0x82cca4db847945ca,0x50d98d9fc890ed4d,
+        0xa37fce126597973c,0xe50ff107bab528a0,
+        0xcc5fc196fefd7d0c,0x1e53ed49a96272c8,
+        0xff77b1fcbebcdc4f,0x25e8e89c13bb0f7a,
+        0x9faacf3df73609b1,0x77b191618c54e9ac,
+        0xc795830d75038c1d,0xd59df5b9ef6a2417,
+        0xf97ae3d0d2446f25,0x4b0573286b44ad1d,
+        0x9becce62836ac577,0x4ee367f9430aec32,
+        0xc2e801fb244576d5,0x229c41f793cda73f,
+        0xf3a20279ed56d48a,0x6b43527578c1110f,
+        0x9845418c345644d6,0x830a13896b78aaa9,
+        0xbe5691ef416bd60c,0x23cc986bc656d553,
+        0xedec366b11c6cb8f,0x2cbfbe86b7ec8aa8,
+        0x94b3a202eb1c3f39,0x7bf7d71432f3d6a9,
+        0xb9e08a83a5e34f07,0xdaf5ccd93fb0cc53,
+        0xe858ad248f5c22c9,0xd1b3400f8f9cff68,
+        0x91376c36d99995be,0x23100809b9c21fa1,
+        0xb58547448ffffb2d,0xabd40a0c2832a78a,
+        0xe2e69915b3fff9f9,0x16c90c8f323f516c,
+        0x8dd01fad907ffc3b,0xae3da7d97f6792e3,
+        0xb1442798f49ffb4a,0x99cd11cfdf41779c,
+        0xdd95317f31c7fa1d,0x40405643d711d583,
+        0x8a7d3eef7f1cfc52,0x482835ea666b2572,
+        0xad1c8eab5ee43b66,0xda3243650005eecf,
+        0xd863b256369d4a40,0x90bed43e40076a82,
+        0x873e4f75e2224e68,0x5a7744a6e804a291,
+        0xa90de3535aaae202,0x711515d0a205cb36,
+        0xd3515c2831559a83,0xd5a5b44ca873e03,
+        0x8412d9991ed58091,0xe858790afe9486c2,
+        0xa5178fff668ae0b6,0x626e974dbe39a872,
+        0xce5d73ff402d98e3,0xfb0a3d212dc8128f,
+        0x80fa687f881c7f8e,0x7ce66634bc9d0b99,
+        0xa139029f6a239f72,0x1c1fffc1ebc44e80,
+        0xc987434744ac874e,0xa327ffb266b56220,
+        0xfbe9141915d7a922,0x4bf1ff9f0062baa8,
+        0x9d71ac8fada6c9b5,0x6f773fc3603db4a9,
+        0xc4ce17b399107c22,0xcb550fb4384d21d3,
+        0xf6019da07f549b2b,0x7e2a53a146606a48,
+        0x99c102844f94e0fb,0x2eda7444cbfc426d,
+        0xc0314325637a1939,0xfa911155fefb5308,
+        0xf03d93eebc589f88,0x793555ab7eba27ca,
+        0x96267c7535b763b5,0x4bc1558b2f3458de,
+        0xbbb01b9283253ca2,0x9eb1aaedfb016f16,
+        0xea9c227723ee8bcb,0x465e15a979c1cadc,
+        0x92a1958a7675175f,0xbfacd89ec191ec9,
+        0xb749faed14125d36,0xcef980ec671f667b,
+        0xe51c79a85916f484,0x82b7e12780e7401a,
+        0x8f31cc0937ae58d2,0xd1b2ecb8b0908810,
+        0xb2fe3f0b8599ef07,0x861fa7e6dcb4aa15,
+        0xdfbdcece67006ac9,0x67a791e093e1d49a,
+        0x8bd6a141006042bd,0xe0c8bb2c5c6d24e0,
+        0xaecc49914078536d,0x58fae9f773886e18,
+        0xda7f5bf590966848,0xaf39a475506a899e,
+        0x888f99797a5e012d,0x6d8406c952429603,
+        0xaab37fd7d8f58178,0xc8e5087ba6d33b83,
+        0xd5605fcdcf32e1d6,0xfb1e4a9a90880a64,
+        0x855c3be0a17fcd26,0x5cf2eea09a55067f,
+        0xa6b34ad8c9dfc06f,0xf42faa48c0ea481e,
+        0xd0601d8efc57b08b,0xf13b94daf124da26,
+        0x823c12795db6ce57,0x76c53d08d6b70858,
+        0xa2cb1717b52481ed,0x54768c4b0c64ca6e,
+        0xcb7ddcdda26da268,0xa9942f5dcf7dfd09,
+        0xfe5d54150b090b02,0xd3f93b35435d7c4c,
+        0x9efa548d26e5a6e1,0xc47bc5014a1a6daf,
+        0xc6b8e9b0709f109a,0x359ab6419ca1091b,
+        0xf867241c8cc6d4c0,0xc30163d203c94b62,
+        0x9b407691d7fc44f8,0x79e0de63425dcf1d,
+        0xc21094364dfb5636,0x985915fc12f542e4,
+        0xf294b943e17a2bc4,0x3e6f5b7b17b2939d,
+        0x979cf3ca6cec5b5a,0xa705992ceecf9c42,
+        0xbd8430bd08277231,0x50c6ff782a838353,
+        0xece53cec4a314ebd,0xa4f8bf5635246428,
+        0x940f4613ae5ed136,0x871b7795e136be99,
+        0xb913179899f68584,0x28e2557b59846e3f,
+        0xe757dd7ec07426e5,0x331aeada2fe589cf,
+        0x9096ea6f3848984f,0x3ff0d2c85def7621,
+        0xb4bca50b065abe63,0xfed077a756b53a9,
+        0xe1ebce4dc7f16dfb,0xd3e8495912c62894,
+        0x8d3360f09cf6e4bd,0x64712dd7abbbd95c,
+        0xb080392cc4349dec,0xbd8d794d96aacfb3,
+        0xdca04777f541c567,0xecf0d7a0fc5583a0,
+        0x89e42caaf9491b60,0xf41686c49db57244,
+        0xac5d37d5b79b6239,0x311c2875c522ced5,
+        0xd77485cb25823ac7,0x7d633293366b828b,
+        0x86a8d39ef77164bc,0xae5dff9c02033197,
+        0xa8530886b54dbdeb,0xd9f57f830283fdfc,
+        0xd267caa862a12d66,0xd072df63c324fd7b,
+        0x8380dea93da4bc60,0x4247cb9e59f71e6d,
+        0xa46116538d0deb78,0x52d9be85f074e608,
+        0xcd795be870516656,0x67902e276c921f8b,
+        0x806bd9714632dff6,0xba1cd8a3db53b6,
+        0xa086cfcd97bf97f3,0x80e8a40eccd228a4,
+        0xc8a883c0fdaf7df0,0x6122cd128006b2cd,
+        0xfad2a4b13d1b5d6c,0x796b805720085f81,
+        0x9cc3a6eec6311a63,0xcbe3303674053bb0,
+        0xc3f490aa77bd60fc,0xbedbfc4411068a9c,
+        0xf4f1b4d515acb93b,0xee92fb5515482d44,
+        0x991711052d8bf3c5,0x751bdd152d4d1c4a,
+        0xbf5cd54678eef0b6,0xd262d45a78a0635d,
+        0xef340a98172aace4,0x86fb897116c87c34,
+        0x9580869f0e7aac0e,0xd45d35e6ae3d4da0,
+        0xbae0a846d2195712,0x8974836059cca109,
+        0xe998d258869facd7,0x2bd1a438703fc94b,
+        0x91ff83775423cc06,0x7b6306a34627ddcf,
+        0xb67f6455292cbf08,0x1a3bc84c17b1d542,
+        0xe41f3d6a7377eeca,0x20caba5f1d9e4a93,
+        0x8e938662882af53e,0x547eb47b7282ee9c,
+        0xb23867fb2a35b28d,0xe99e619a4f23aa43,
+        0xdec681f9f4c31f31,0x6405fa00e2ec94d4,
+        0x8b3c113c38f9f37e,0xde83bc408dd3dd04,
+        0xae0b158b4738705e,0x9624ab50b148d445,
+        0xd98ddaee19068c76,0x3badd624dd9b0957,
+        0x87f8a8d4cfa417c9,0xe54ca5d70a80e5d6,
+        0xa9f6d30a038d1dbc,0x5e9fcf4ccd211f4c,
+        0xd47487cc8470652b,0x7647c3200069671f,
+        0x84c8d4dfd2c63f3b,0x29ecd9f40041e073,
+        0xa5fb0a17c777cf09,0xf468107100525890,
+        0xcf79cc9db955c2cc,0x7182148d4066eeb4,
+        0x81ac1fe293d599bf,0xc6f14cd848405530,
+        0xa21727db38cb002f,0xb8ada00e5a506a7c,
+        0xca9cf1d206fdc03b,0xa6d90811f0e4851c,
+        0xfd442e4688bd304a,0x908f4a166d1da663,
+        0x9e4a9cec15763e2e,0x9a598e4e043287fe,
+        0xc5dd44271ad3cdba,0x40eff1e1853f29fd,
+        0xf7549530e188c128,0xd12bee59e68ef47c,
+        0x9a94dd3e8cf578b9,0x82bb74f8301958ce,
+        0xc13a148e3032d6e7,0xe36a52363c1faf01,
+        0xf18899b1bc3f8ca1,0xdc44e6c3cb279ac1,
+        0x96f5600f15a7b7e5,0x29ab103a5ef8c0b9,
+        0xbcb2b812db11a5de,0x7415d448f6b6f0e7,
+        0xebdf661791d60f56,0x111b495b3464ad21,
+        0x936b9fcebb25c995,0xcab10dd900beec34,
+        0xb84687c269ef3bfb,0x3d5d514f40eea742,
+        0xe65829b3046b0afa,0xcb4a5a3112a5112,
+        0x8ff71a0fe2c2e6dc,0x47f0e785eaba72ab,
+        0xb3f4e093db73a093,0x59ed216765690f56,
+        0xe0f218b8d25088b8,0x306869c13ec3532c,
+        0x8c974f7383725573,0x1e414218c73a13fb,
+        0xafbd2350644eeacf,0xe5d1929ef90898fa,
+        0xdbac6c247d62a583,0xdf45f746b74abf39,
+        0x894bc396ce5da772,0x6b8bba8c328eb783,
+        0xab9eb47c81f5114f,0x66ea92f3f326564,
+        0xd686619ba27255a2,0xc80a537b0efefebd,
+        0x8613fd0145877585,0xbd06742ce95f5f36,
+        0xa798fc4196e952e7,0x2c48113823b73704,
+        0xd17f3b51fca3a7a0,0xf75a15862ca504c5,
+        0x82ef85133de648c4,0x9a984d73dbe722fb,
+        0xa3ab66580d5fdaf5,0xc13e60d0d2e0ebba,
+        0xcc963fee10b7d1b3,0x318df905079926a8,
+        0xffbbcfe994e5c61f,0xfdf17746497f7052,
+        0x9fd561f1fd0f9bd3,0xfeb6ea8bedefa633,
+        0xc7caba6e7c5382c8,0xfe64a52ee96b8fc0,
+        0xf9bd690a1b68637b,0x3dfdce7aa3c673b0,
+        0x9c1661a651213e2d,0x6bea10ca65c084e,
+        0xc31bfa0fe5698db8,0x486e494fcff30a62,
+        0xf3e2f893dec3f126,0x5a89dba3c3efccfa,
+        0x986ddb5c6b3a76b7,0xf89629465a75e01c,
+        0xbe89523386091465,0xf6bbb397f1135823,
+        0xee2ba6c0678b597f,0x746aa07ded582e2c,
+        0x94db483840b717ef,0xa8c2a44eb4571cdc,
+        0xba121a4650e4ddeb,0x92f34d62616ce413,
+        0xe896a0d7e51e1566,0x77b020baf9c81d17,
+        0x915e2486ef32cd60,0xace1474dc1d122e,
+        0xb5b5ada8aaff80b8,0xd819992132456ba,
+        0xe3231912d5bf60e6,0x10e1fff697ed6c69,
+        0x8df5efabc5979c8f,0xca8d3ffa1ef463c1,
+        0xb1736b96b6fd83b3,0xbd308ff8a6b17cb2,
+        0xddd0467c64bce4a0,0xac7cb3f6d05ddbde,
+        0x8aa22c0dbef60ee4,0x6bcdf07a423aa96b,
+        0xad4ab7112eb3929d,0x86c16c98d2c953c6,
+        0xd89d64d57a607744,0xe871c7bf077ba8b7,
+        0x87625f056c7c4a8b,0x11471cd764ad4972,
+        0xa93af6c6c79b5d2d,0xd598e40d3dd89bcf,
+        0xd389b47879823479,0x4aff1d108d4ec2c3,
+        0x843610cb4bf160cb,0xcedf722a585139ba,
+        0xa54394fe1eedb8fe,0xc2974eb4ee658828,
+        0xce947a3da6a9273e,0x733d226229feea32,
+        0x811ccc668829b887,0x806357d5a3f525f,
+        0xa163ff802a3426a8,0xca07c2dcb0cf26f7,
+        0xc9bcff6034c13052,0xfc89b393dd02f0b5,
+        0xfc2c3f3841f17c67,0xbbac2078d443ace2,
+        0x9d9ba7832936edc0,0xd54b944b84aa4c0d,
+        0xc5029163f384a931,0xa9e795e65d4df11,
+        0xf64335bcf065d37d,0x4d4617b5ff4a16d5,
+        0x99ea0196163fa42e,0x504bced1bf8e4e45,
+        0xc06481fb9bcf8d39,0xe45ec2862f71e1d6,
+        0xf07da27a82c37088,0x5d767327bb4e5a4c,
+        0x964e858c91ba2655,0x3a6a07f8d510f86f,
+        0xbbe226efb628afea,0x890489f70a55368b,
+        0xeadab0aba3b2dbe5,0x2b45ac74ccea842e,
+        0x92c8ae6b464fc96f,0x3b0b8bc90012929d,
+        0xb77ada0617e3bbcb,0x9ce6ebb40173744,
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+        0xb38d92d760ec4455,0x37c981dcc395a9ac,
+        0xe070f78d3927556a,0x85bbe253f47b1417,
+        0x8c469ab843b89562,0x93956d7478ccec8e,
+        0xaf58416654a6babb,0x387ac8d1970027b2,
+        0xdb2e51bfe9d0696a,0x6997b05fcc0319e,
+        0x88fcf317f22241e2,0x441fece3bdf81f03,
+        0xab3c2fddeeaad25a,0xd527e81cad7626c3,
+        0xd60b3bd56a5586f1,0x8a71e223d8d3b074,
+        0x85c7056562757456,0xf6872d5667844e49,
+        0xa738c6bebb12d16c,0xb428f8ac016561db,
+        0xd106f86e69d785c7,0xe13336d701beba52,
+        0x82a45b450226b39c,0xecc0024661173473,
+        0xa34d721642b06084,0x27f002d7f95d0190,
+        0xcc20ce9bd35c78a5,0x31ec038df7b441f4,
+        0xff290242c83396ce,0x7e67047175a15271,
+        0x9f79a169bd203e41,0xf0062c6e984d386,
+        0xc75809c42c684dd1,0x52c07b78a3e60868,
+        0xf92e0c3537826145,0xa7709a56ccdf8a82,
+        0x9bbcc7a142b17ccb,0x88a66076400bb691,
+        0xc2abf989935ddbfe,0x6acff893d00ea435,
+        0xf356f7ebf83552fe,0x583f6b8c4124d43,
+        0x98165af37b2153de,0xc3727a337a8b704a,
+        0xbe1bf1b059e9a8d6,0x744f18c0592e4c5c,
+        0xeda2ee1c7064130c,0x1162def06f79df73,
+        0x9485d4d1c63e8be7,0x8addcb5645ac2ba8,
+        0xb9a74a0637ce2ee1,0x6d953e2bd7173692,
+        0xe8111c87c5c1ba99,0xc8fa8db6ccdd0437,
+        0x910ab1d4db9914a0,0x1d9c9892400a22a2,
+        0xb54d5e4a127f59c8,0x2503beb6d00cab4b,
+        0xe2a0b5dc971f303a,0x2e44ae64840fd61d,
+        0x8da471a9de737e24,0x5ceaecfed289e5d2,
+        0xb10d8e1456105dad,0x7425a83e872c5f47,
+        0xdd50f1996b947518,0xd12f124e28f77719,
+        0x8a5296ffe33cc92f,0x82bd6b70d99aaa6f,
+        0xace73cbfdc0bfb7b,0x636cc64d1001550b,
+        0xd8210befd30efa5a,0x3c47f7e05401aa4e,
+        0x8714a775e3e95c78,0x65acfaec34810a71,
+        0xa8d9d1535ce3b396,0x7f1839a741a14d0d,
+        0xd31045a8341ca07c,0x1ede48111209a050,
+        0x83ea2b892091e44d,0x934aed0aab460432,
+        0xa4e4b66b68b65d60,0xf81da84d5617853f,
+        0xce1de40642e3f4b9,0x36251260ab9d668e,
+        0x80d2ae83e9ce78f3,0xc1d72b7c6b426019,
+        0xa1075a24e4421730,0xb24cf65b8612f81f,
+        0xc94930ae1d529cfc,0xdee033f26797b627,
+        0xfb9b7cd9a4a7443c,0x169840ef017da3b1,
+        0x9d412e0806e88aa5,0x8e1f289560ee864e,
+        0xc491798a08a2ad4e,0xf1a6f2bab92a27e2,
+        0xf5b5d7ec8acb58a2,0xae10af696774b1db,
+        0x9991a6f3d6bf1765,0xacca6da1e0a8ef29,
+        0xbff610b0cc6edd3f,0x17fd090a58d32af3,
+        0xeff394dcff8a948e,0xddfc4b4cef07f5b0,
+        0x95f83d0a1fb69cd9,0x4abdaf101564f98e,
+        0xbb764c4ca7a4440f,0x9d6d1ad41abe37f1,
+        0xea53df5fd18d5513,0x84c86189216dc5ed,
+        0x92746b9be2f8552c,0x32fd3cf5b4e49bb4,
+        0xb7118682dbb66a77,0x3fbc8c33221dc2a1,
+        0xe4d5e82392a40515,0xfabaf3feaa5334a,
+        0x8f05b1163ba6832d,0x29cb4d87f2a7400e,
+        0xb2c71d5bca9023f8,0x743e20e9ef511012,
+        0xdf78e4b2bd342cf6,0x914da9246b255416,
+        0x8bab8eefb6409c1a,0x1ad089b6c2f7548e,
+        0xae9672aba3d0c320,0xa184ac2473b529b1,
+        0xda3c0f568cc4f3e8,0xc9e5d72d90a2741e,
+        0x8865899617fb1871,0x7e2fa67c7a658892,
+        0xaa7eebfb9df9de8d,0xddbb901b98feeab7,
+        0xd51ea6fa85785631,0x552a74227f3ea565,
+        0x8533285c936b35de,0xd53a88958f87275f,
+        0xa67ff273b8460356,0x8a892abaf368f137,
+        0xd01fef10a657842c,0x2d2b7569b0432d85,
+        0x8213f56a67f6b29b,0x9c3b29620e29fc73,
+        0xa298f2c501f45f42,0x8349f3ba91b47b8f,
+        0xcb3f2f7642717713,0x241c70a936219a73,
+        0xfe0efb53d30dd4d7,0xed238cd383aa0110,
+        0x9ec95d1463e8a506,0xf4363804324a40aa,
+        0xc67bb4597ce2ce48,0xb143c6053edcd0d5,
+        0xf81aa16fdc1b81da,0xdd94b7868e94050a,
+        0x9b10a4e5e9913128,0xca7cf2b4191c8326,
+        0xc1d4ce1f63f57d72,0xfd1c2f611f63a3f0,
+        0xf24a01a73cf2dccf,0xbc633b39673c8cec,
+        0x976e41088617ca01,0xd5be0503e085d813,
+        0xbd49d14aa79dbc82,0x4b2d8644d8a74e18,
+        0xec9c459d51852ba2,0xddf8e7d60ed1219e,
+        0x93e1ab8252f33b45,0xcabb90e5c942b503,
+        0xb8da1662e7b00a17,0x3d6a751f3b936243,
+        0xe7109bfba19c0c9d,0xcc512670a783ad4,
+        0x906a617d450187e2,0x27fb2b80668b24c5,
+        0xb484f9dc9641e9da,0xb1f9f660802dedf6,
+        0xe1a63853bbd26451,0x5e7873f8a0396973,
+        0x8d07e33455637eb2,0xdb0b487b6423e1e8,
+        0xb049dc016abc5e5f,0x91ce1a9a3d2cda62,
+        0xdc5c5301c56b75f7,0x7641a140cc7810fb,
+        0x89b9b3e11b6329ba,0xa9e904c87fcb0a9d,
+        0xac2820d9623bf429,0x546345fa9fbdcd44,
+        0xd732290fbacaf133,0xa97c177947ad4095,
+        0x867f59a9d4bed6c0,0x49ed8eabcccc485d,
+        0xa81f301449ee8c70,0x5c68f256bfff5a74,
+        0xd226fc195c6a2f8c,0x73832eec6fff3111,
+        0x83585d8fd9c25db7,0xc831fd53c5ff7eab,
+        0xa42e74f3d032f525,0xba3e7ca8b77f5e55,
+        0xcd3a1230c43fb26f,0x28ce1bd2e55f35eb,
+        0x80444b5e7aa7cf85,0x7980d163cf5b81b3,
+        0xa0555e361951c366,0xd7e105bcc332621f,
+        0xc86ab5c39fa63440,0x8dd9472bf3fefaa7,
+        0xfa856334878fc150,0xb14f98f6f0feb951,
+        0x9c935e00d4b9d8d2,0x6ed1bf9a569f33d3,
+        0xc3b8358109e84f07,0xa862f80ec4700c8,
+        0xf4a642e14c6262c8,0xcd27bb612758c0fa,
+        0x98e7e9cccfbd7dbd,0x8038d51cb897789c,
+        0xbf21e44003acdd2c,0xe0470a63e6bd56c3,
+        0xeeea5d5004981478,0x1858ccfce06cac74,
+        0x95527a5202df0ccb,0xf37801e0c43ebc8,
+        0xbaa718e68396cffd,0xd30560258f54e6ba,
+        0xe950df20247c83fd,0x47c6b82ef32a2069,
+        0x91d28b7416cdd27e,0x4cdc331d57fa5441,
+        0xb6472e511c81471d,0xe0133fe4adf8e952,
+        0xe3d8f9e563a198e5,0x58180fddd97723a6,
+        0x8e679c2f5e44ff8f,0x570f09eaa7ea7648,};
+using powers = powers_template<>;
+
+}
+
+#endif
diff --git a/libstdc++-v3/src/c++17/fast_float/float_common.h b/libstdc++-v3/src/c++17/fast_float/float_common.h
new file mode 100644
index 00000000000..c8e7e4fc99e
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/float_common.h
@@ -0,0 +1,362 @@
+#ifndef FASTFLOAT_FLOAT_COMMON_H
+#define FASTFLOAT_FLOAT_COMMON_H
+
+#include <cfloat>
+#include <cstdint>
+#include <cassert>
+#include <cstring>
+
+#if (defined(__x86_64) || defined(__x86_64__) || defined(_M_X64)   \
+       || defined(__amd64) || defined(__aarch64__) || defined(_M_ARM64) \
+       || defined(__MINGW64__)                                          \
+       || defined(__s390x__)                                            \
+       || (defined(__ppc64__) || defined(__PPC64__) || defined(__ppc64le__) || defined(__PPC64LE__)) \
+       || defined(__EMSCRIPTEN__))
+#define FASTFLOAT_64BIT
+#elif (defined(__i386) || defined(__i386__) || defined(_M_IX86)   \
+     || defined(__arm__) || defined(_M_ARM)                   \
+     || defined(__MINGW32__))
+#define FASTFLOAT_32BIT
+#else
+  // Need to check incrementally, since SIZE_MAX is a size_t, avoid overflow.
+  // We can never tell the register width, but the SIZE_MAX is a good approximation.
+  // UINTPTR_MAX and INTPTR_MAX are optional, so avoid them for max portability.
+  #if SIZE_MAX == 0xffff
+    #error Unknown platform (16-bit, unsupported)
+  #elif SIZE_MAX == 0xffffffff
+    #define FASTFLOAT_32BIT
+  #elif SIZE_MAX == 0xffffffffffffffff
+    #define FASTFLOAT_64BIT
+  #else
+    #error Unknown platform (not 32-bit, not 64-bit?)
+  #endif
+#endif
+
+#if ((defined(_WIN32) || defined(_WIN64)) && !defined(__clang__))
+#include <intrin.h>
+#endif
+
+#if defined(_MSC_VER) && !defined(__clang__)
+#define FASTFLOAT_VISUAL_STUDIO 1
+#endif
+
+#ifdef _WIN32
+#define FASTFLOAT_IS_BIG_ENDIAN 0
+#else
+#if defined(__APPLE__) || defined(__FreeBSD__)
+#include <machine/endian.h>
+#elif defined(sun) || defined(__sun)
+#include <sys/byteorder.h>
+#else
+#include <endian.h>
+#endif
+#
+#ifndef __BYTE_ORDER__
+// safe choice
+#define FASTFLOAT_IS_BIG_ENDIAN 0
+#endif
+#
+#ifndef __ORDER_LITTLE_ENDIAN__
+// safe choice
+#define FASTFLOAT_IS_BIG_ENDIAN 0
+#endif
+#
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define FASTFLOAT_IS_BIG_ENDIAN 0
+#else
+#define FASTFLOAT_IS_BIG_ENDIAN 1
+#endif
+#endif
+
+#ifdef FASTFLOAT_VISUAL_STUDIO
+#define fastfloat_really_inline __forceinline
+#else
+#define fastfloat_really_inline inline __attribute__((always_inline))
+#endif
+
+#ifndef FASTFLOAT_ASSERT
+#define FASTFLOAT_ASSERT(x)  { if (!(x)) abort(); }
+#endif
+
+#ifndef FASTFLOAT_DEBUG_ASSERT
+#include <cassert>
+#define FASTFLOAT_DEBUG_ASSERT(x) assert(x)
+#endif
+
+// rust style `try!()` macro, or `?` operator
+#define FASTFLOAT_TRY(x) { if (!(x)) return false; }
+
+namespace fast_float {
+
+// Compares two ASCII strings in a case insensitive manner.
+inline bool fastfloat_strncasecmp(const char *input1, const char *input2,
+                                  size_t length) {
+  char running_diff{0};
+  for (size_t i = 0; i < length; i++) {
+    running_diff |= (input1[i] ^ input2[i]);
+  }
+  return (running_diff == 0) || (running_diff == 32);
+}
+
+#ifndef FLT_EVAL_METHOD
+#error "FLT_EVAL_METHOD should be defined, please include cfloat."
+#endif
+
+// a pointer and a length to a contiguous block of memory
+template <typename T>
+struct span {
+  const T* ptr;
+  size_t length;
+  span(const T* _ptr, size_t _length) : ptr(_ptr), length(_length) {}
+  span() : ptr(nullptr), length(0) {}
+
+  constexpr size_t len() const noexcept {
+    return length;
+  }
+
+  const T& operator[](size_t index) const noexcept {
+    FASTFLOAT_DEBUG_ASSERT(index < length);
+    return ptr[index];
+  }
+};
+
+struct value128 {
+  uint64_t low;
+  uint64_t high;
+  value128(uint64_t _low, uint64_t _high) : low(_low), high(_high) {}
+  value128() : low(0), high(0) {}
+};
+
+/* result might be undefined when input_num is zero */
+fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
+  assert(input_num > 0);
+#ifdef FASTFLOAT_VISUAL_STUDIO
+  #if defined(_M_X64) || defined(_M_ARM64)
+  unsigned long leading_zero = 0;
+  // Search the mask data from most significant bit (MSB)
+  // to least significant bit (LSB) for a set bit (1).
+  _BitScanReverse64(&leading_zero, input_num);
+  return (int)(63 - leading_zero);
+  #else
+  int last_bit = 0;
+  if(input_num & uint64_t(0xffffffff00000000)) input_num >>= 32, last_bit |= 32;
+  if(input_num & uint64_t(        0xffff0000)) input_num >>= 16, last_bit |= 16;
+  if(input_num & uint64_t(            0xff00)) input_num >>=  8, last_bit |=  8;
+  if(input_num & uint64_t(              0xf0)) input_num >>=  4, last_bit |=  4;
+  if(input_num & uint64_t(               0xc)) input_num >>=  2, last_bit |=  2;
+  if(input_num & uint64_t(               0x2)) input_num >>=  1, last_bit |=  1;
+  return 63 - last_bit;
+  #endif
+#else
+  return __builtin_clzll(input_num);
+#endif
+}
+
+#ifdef FASTFLOAT_32BIT
+
+// slow emulation routine for 32-bit
+fastfloat_really_inline uint64_t emulu(uint32_t x, uint32_t y) {
+    return x * (uint64_t)y;
+}
+
+// slow emulation routine for 32-bit
+#if !defined(__MINGW64__)
+fastfloat_really_inline uint64_t _umul128(uint64_t ab, uint64_t cd,
+                                          uint64_t *hi) {
+  uint64_t ad = emulu((uint32_t)(ab >> 32), (uint32_t)cd);
+  uint64_t bd = emulu((uint32_t)ab, (uint32_t)cd);
+  uint64_t adbc = ad + emulu((uint32_t)ab, (uint32_t)(cd >> 32));
+  uint64_t adbc_carry = !!(adbc < ad);
+  uint64_t lo = bd + (adbc << 32);
+  *hi = emulu((uint32_t)(ab >> 32), (uint32_t)(cd >> 32)) + (adbc >> 32) +
+        (adbc_carry << 32) + !!(lo < bd);
+  return lo;
+}
+#endif // !__MINGW64__
+
+#endif // FASTFLOAT_32BIT
+
+
+// compute 64-bit a*b
+fastfloat_really_inline value128 full_multiplication(uint64_t a,
+                                                     uint64_t b) {
+  value128 answer;
+#ifdef _M_ARM64
+  // ARM64 has native support for 64-bit multiplications, no need to emulate
+  answer.high = __umulh(a, b);
+  answer.low = a * b;
+#elif defined(FASTFLOAT_32BIT) || (defined(_WIN64) && !defined(__clang__))
+  answer.low = _umul128(a, b, &answer.high); // _umul128 not available on ARM64
+#elif defined(FASTFLOAT_64BIT)
+  __uint128_t r = ((__uint128_t)a) * b;
+  answer.low = uint64_t(r);
+  answer.high = uint64_t(r >> 64);
+#else
+  #error Not implemented
+#endif
+  return answer;
+}
+
+struct adjusted_mantissa {
+  uint64_t mantissa{0};
+  int32_t power2{0}; // a negative value indicates an invalid result
+  adjusted_mantissa() = default;
+  bool operator==(const adjusted_mantissa &o) const {
+    return mantissa == o.mantissa && power2 == o.power2;
+  }
+  bool operator!=(const adjusted_mantissa &o) const {
+    return mantissa != o.mantissa || power2 != o.power2;
+  }
+};
+
+// Bias so we can get the real exponent with an invalid adjusted_mantissa.
+constexpr static int32_t invalid_am_bias = -0x8000;
+
+constexpr static double powers_of_ten_double[] = {
+    1e0,  1e1,  1e2,  1e3,  1e4,  1e5,  1e6,  1e7,  1e8,  1e9,  1e10, 1e11,
+    1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22};
+constexpr static float powers_of_ten_float[] = {1e0, 1e1, 1e2, 1e3, 1e4, 1e5,
+                                                1e6, 1e7, 1e8, 1e9, 1e10};
+
+template <typename T> struct binary_format {
+  static inline constexpr int mantissa_explicit_bits();
+  static inline constexpr int minimum_exponent();
+  static inline constexpr int infinite_power();
+  static inline constexpr int sign_index();
+  static inline constexpr int min_exponent_fast_path();
+  static inline constexpr int max_exponent_fast_path();
+  static inline constexpr int max_exponent_round_to_even();
+  static inline constexpr int min_exponent_round_to_even();
+  static inline constexpr uint64_t max_mantissa_fast_path();
+  static inline constexpr int largest_power_of_ten();
+  static inline constexpr int smallest_power_of_ten();
+  static inline constexpr T exact_power_of_ten(int64_t power);
+  static inline constexpr size_t max_digits();
+};
+
+template <> inline constexpr int binary_format<double>::mantissa_explicit_bits() {
+  return 52;
+}
+template <> inline constexpr int binary_format<float>::mantissa_explicit_bits() {
+  return 23;
+}
+
+template <> inline constexpr int binary_format<double>::max_exponent_round_to_even() {
+  return 23;
+}
+
+template <> inline constexpr int binary_format<float>::max_exponent_round_to_even() {
+  return 10;
+}
+
+template <> inline constexpr int binary_format<double>::min_exponent_round_to_even() {
+  return -4;
+}
+
+template <> inline constexpr int binary_format<float>::min_exponent_round_to_even() {
+  return -17;
+}
+
+template <> inline constexpr int binary_format<double>::minimum_exponent() {
+  return -1023;
+}
+template <> inline constexpr int binary_format<float>::minimum_exponent() {
+  return -127;
+}
+
+template <> inline constexpr int binary_format<double>::infinite_power() {
+  return 0x7FF;
+}
+template <> inline constexpr int binary_format<float>::infinite_power() {
+  return 0xFF;
+}
+
+template <> inline constexpr int binary_format<double>::sign_index() { return 63; }
+template <> inline constexpr int binary_format<float>::sign_index() { return 31; }
+
+template <> inline constexpr int binary_format<double>::min_exponent_fast_path() {
+#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
+  return 0;
+#else
+  return -22;
+#endif
+}
+template <> inline constexpr int binary_format<float>::min_exponent_fast_path() {
+#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
+  return 0;
+#else
+  return -10;
+#endif
+}
+
+template <> inline constexpr int binary_format<double>::max_exponent_fast_path() {
+  return 22;
+}
+template <> inline constexpr int binary_format<float>::max_exponent_fast_path() {
+  return 10;
+}
+
+template <> inline constexpr uint64_t binary_format<double>::max_mantissa_fast_path() {
+  return uint64_t(2) << mantissa_explicit_bits();
+}
+template <> inline constexpr uint64_t binary_format<float>::max_mantissa_fast_path() {
+  return uint64_t(2) << mantissa_explicit_bits();
+}
+
+template <>
+inline constexpr double binary_format<double>::exact_power_of_ten(int64_t power) {
+  return powers_of_ten_double[power];
+}
+template <>
+inline constexpr float binary_format<float>::exact_power_of_ten(int64_t power) {
+
+  return powers_of_ten_float[power];
+}
+
+
+template <>
+inline constexpr int binary_format<double>::largest_power_of_ten() {
+  return 308;
+}
+template <>
+inline constexpr int binary_format<float>::largest_power_of_ten() {
+  return 38;
+}
+
+template <>
+inline constexpr int binary_format<double>::smallest_power_of_ten() {
+  return -342;
+}
+template <>
+inline constexpr int binary_format<float>::smallest_power_of_ten() {
+  return -65;
+}
+
+template <> inline constexpr size_t binary_format<double>::max_digits() {
+  return 769;
+}
+template <> inline constexpr size_t binary_format<float>::max_digits() {
+  return 114;
+}
+
+template<typename T>
+fastfloat_really_inline void to_float(bool negative, adjusted_mantissa am, T &value) {
+  uint64_t word = am.mantissa;
+  word |= uint64_t(am.power2) << binary_format<T>::mantissa_explicit_bits();
+  word = negative
+  ? word | (uint64_t(1) << binary_format<T>::sign_index()) : word;
+#if FASTFLOAT_IS_BIG_ENDIAN == 1
+   if (std::is_same<T, float>::value) {
+     ::memcpy(&value, (char *)&word + 4, sizeof(T)); // extract value at offset 4-7 if float on big-endian
+   } else {
+     ::memcpy(&value, &word, sizeof(T));
+   }
+#else
+   // For little-endian systems:
+   ::memcpy(&value, &word, sizeof(T));
+#endif
+}
+
+} // namespace fast_float
+
+#endif
diff --git a/libstdc++-v3/src/c++17/fast_float/parse_number.h b/libstdc++-v3/src/c++17/fast_float/parse_number.h
new file mode 100644
index 00000000000..62ae3b039e6
--- /dev/null
+++ b/libstdc++-v3/src/c++17/fast_float/parse_number.h
@@ -0,0 +1,113 @@
+#ifndef FASTFLOAT_PARSE_NUMBER_H
+#define FASTFLOAT_PARSE_NUMBER_H
+
+#include "ascii_number.h"
+#include "decimal_to_binary.h"
+#include "digit_comparison.h"
+
+#include <cmath>
+#include <cstring>
+#include <limits>
+#include <system_error>
+
+namespace fast_float {
+
+
+namespace detail {
+/**
+ * Special case +inf, -inf, nan, infinity, -infinity.
+ * The case comparisons could be made much faster given that we know that the
+ * strings a null-free and fixed.
+ **/
+template <typename T>
+from_chars_result parse_infnan(const char *first, const char *last, T &value)  noexcept  {
+  from_chars_result answer;
+  answer.ptr = first;
+  answer.ec = std::errc(); // be optimistic
+  bool minusSign = false;
+  if (*first == '-') { // assume first < last, so dereference without checks; C++17 20.19.3.(7.1) explicitly forbids '+' here
+      minusSign = true;
+      ++first;
+  }
+  if (last - first >= 3) {
+    if (fastfloat_strncasecmp(first, "nan", 3)) {
+      answer.ptr = (first += 3);
+      value = minusSign ? -std::numeric_limits<T>::quiet_NaN() : std::numeric_limits<T>::quiet_NaN();
+      // Check for possible nan(n-char-seq-opt), C++17 20.19.3.7, C11 7.20.1.3.3. At least MSVC produces nan(ind) and nan(snan).
+      if(first != last && *first == '(') {
+        for(const char* ptr = first + 1; ptr != last; ++ptr) {
+          if (*ptr == ')') {
+            answer.ptr = ptr + 1; // valid nan(n-char-seq-opt)
+            break;
+          }
+          else if(!(('a' <= *ptr && *ptr <= 'z') || ('A' <= *ptr && *ptr <= 'Z') || ('0' <= *ptr && *ptr <= '9') || *ptr == '_'))
+            break; // forbidden char, not nan(n-char-seq-opt)
+        }
+      }
+      return answer;
+    }
+    if (fastfloat_strncasecmp(first, "inf", 3)) {
+      if ((last - first >= 8) && fastfloat_strncasecmp(first + 3, "inity", 5)) {
+        answer.ptr = first + 8;
+      } else {
+        answer.ptr = first + 3;
+      }
+      value = minusSign ? -std::numeric_limits<T>::infinity() : std::numeric_limits<T>::infinity();
+      return answer;
+    }
+  }
+  answer.ec = std::errc::invalid_argument;
+  return answer;
+}
+
+} // namespace detail
+
+template<typename T>
+from_chars_result from_chars(const char *first, const char *last,
+                             T &value, chars_format fmt /*= chars_format::general*/)  noexcept  {
+  return from_chars_advanced(first, last, value, parse_options{fmt});
+}
+
+template<typename T>
+from_chars_result from_chars_advanced(const char *first, const char *last,
+                                      T &value, parse_options options)  noexcept  {
+
+  static_assert (std::is_same<T, double>::value || std::is_same<T, float>::value, "only float and double are supported");
+
+
+  from_chars_result answer;
+  if (first == last) {
+    answer.ec = std::errc::invalid_argument;
+    answer.ptr = first;
+    return answer;
+  }
+  parsed_number_string pns = parse_number_string(first, last, options);
+  if (!pns.valid) {
+    return detail::parse_infnan(first, last, value);
+  }
+  answer.ec = std::errc(); // be optimistic
+  answer.ptr = pns.lastmatch;
+  // Next is Clinger's fast path.
+  if (binary_format<T>::min_exponent_fast_path() <= pns.exponent && pns.exponent <= binary_format<T>::max_exponent_fast_path() && pns.mantissa <=binary_format<T>::max_mantissa_fast_path() && !pns.too_many_digits) {
+    value = T(pns.mantissa);
+    if (pns.exponent < 0) { value = value / binary_format<T>::exact_power_of_ten(-pns.exponent); }
+    else { value = value * binary_format<T>::exact_power_of_ten(pns.exponent); }
+    if (pns.negative) { value = -value; }
+    return answer;
+  }
+  adjusted_mantissa am = compute_float<binary_format<T>>(pns.exponent, pns.mantissa);
+  if(pns.too_many_digits && am.power2 >= 0) {
+    if(am != compute_float<binary_format<T>>(pns.exponent, pns.mantissa + 1)) {
+      am = compute_error<binary_format<T>>(pns.exponent, pns.mantissa);
+    }
+  }
+  // If we called compute_float<binary_format<T>>(pns.exponent, pns.mantissa) and we have an invalid power (am.power2 < 0),
+  // then we need to go the long way around again. This is very uncommon.
+  if(am.power2 < 0) { am = digit_comp<T>(pns, am); }
+  to_float(pns.negative, am, value);
+  return answer;
+}
+
+} // namespace fast_float
+
+#endif
-- 
2.34.0



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