fast_float: float_common.h: Support RISC-V

src/3rdparty/fast_float/constexpr_feature_detect.h

@@ -0,0 +1,53 @@
+#ifndef FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H
+#define FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H
+
+#ifdef __has_include
+#if __has_include(<version>)
+#include <version>
+#endif
+#endif
+
+// Testing for https://wg21.link/N3652, adopted in C++14
+#if defined(__cpp_constexpr) && __cpp_constexpr >= 201304
+#define FASTFLOAT_CONSTEXPR14 constexpr
+#else
+#define FASTFLOAT_CONSTEXPR14
+#endif
+
+#if defined(__cpp_lib_bit_cast) && __cpp_lib_bit_cast >= 201806L
+#define FASTFLOAT_HAS_BIT_CAST 1
+#else
+#define FASTFLOAT_HAS_BIT_CAST 0
+#endif
+
+#if defined(__cpp_lib_is_constant_evaluated) &&                                \
+    __cpp_lib_is_constant_evaluated >= 201811L
+#define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 1
+#else
+#define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 0
+#endif
+
+#if defined(__cpp_if_constexpr) && __cpp_if_constexpr >= 201606L
+#define FASTFLOAT_IF_CONSTEXPR17(x) if constexpr (x)
+#else
+#define FASTFLOAT_IF_CONSTEXPR17(x) if (x)
+#endif
+
+// Testing for relevant C++20 constexpr library features
+#if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED && FASTFLOAT_HAS_BIT_CAST &&           \
+    defined(__cpp_lib_constexpr_algorithms) &&                                 \
+    __cpp_lib_constexpr_algorithms >= 201806L /*For std::copy and std::fill*/
+#define FASTFLOAT_CONSTEXPR20 constexpr
+#define FASTFLOAT_IS_CONSTEXPR 1
+#else
+#define FASTFLOAT_CONSTEXPR20
+#define FASTFLOAT_IS_CONSTEXPR 0
+#endif
+
+#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+#define FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE 0
+#else
+#define FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE 1
+#endif
+
+#endif // FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H

src/3rdparty/fast_float/decimal_to_binary.h

@@ -0,0 +1,212 @@
+#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 FASTFLOAT_CONSTEXPR20 value128
+compute_product_approximation(int64_t q, uint64_t w) {
+  int const 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 FASTFLOAT_CONSTEXPR14 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 FASTFLOAT_CONSTEXPR20 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);
+}
+
+// Computers w * 10 ** q.
+// The returned value should be a valid number that simply needs 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 FASTFLOAT_CONSTEXPR20 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);
+  // The computed 'product' is always sufficient.
+  // Mathematical proof:
+  // Noble Mushtak and Daniel Lemire, Fast Number Parsing Without Fallback (to
+  // appear) See script/mushtak_lemire.py
+
+  // 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);
+  int shift = upperbit + 64 - binary::mantissa_explicit_bits() - 3;
+
+  answer.mantissa = product.high >> shift;
+
+  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 in the 32-bit and
+    // and 64-bit case (with no more than 19 digits).
+    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 << shift) == 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