[libc][math][c23] adds nanf128 (#85201)

Continuing #84689, this one required more changes than the others, so I
am making it a separate PR.

Extends some stuff in `str_to_float.h`, `str_to_integer.h` to work on
types wider than `unsigned long long` and `uint64_t`.

cc @lntue for review.

Author: Michael Flanders

libc/config/linux/aarch64/entrypoints.txt

@@ -468,6 +468,7 @@ if(LIBC_TYPES_HAS_FLOAT128)
     libc.src.math.lrintf128
     libc.src.math.lroundf128
     libc.src.math.modff128
+    libc.src.math.nanf128
     libc.src.math.nextafterf128
     libc.src.math.rintf128
     libc.src.math.roundf128

libc/config/linux/riscv/entrypoints.txt

@@ -476,6 +476,7 @@ if(LIBC_TYPES_HAS_FLOAT128)
     libc.src.math.lrintf128
     libc.src.math.lroundf128
     libc.src.math.modff128
+    libc.src.math.nanf128
     libc.src.math.nextafterf128
     libc.src.math.rintf128
     libc.src.math.roundf128

libc/config/linux/x86_64/entrypoints.txt

@@ -481,6 +481,7 @@ if(LIBC_TYPES_HAS_FLOAT128)
     libc.src.math.lrintf128
     libc.src.math.lroundf128
     libc.src.math.modff128
+    libc.src.math.nanf128
     libc.src.math.nextafterf128
     libc.src.math.rintf128
     libc.src.math.roundf128

libc/docs/math/index.rst

@@ -259,6 +259,8 @@ Basic Operations
 +--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
 | nanl         | |check| | |check| | |check| | |check| | |check| |         |         | |check| | |check| | |check| |         |         |
 +--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
+| nanf128      | |check| | |check| |         | |check| |         |         |         |         |         |         |         |         |
++--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
 | nearbyint    | |check| | |check| | |check| | |check| | |check| |         |         | |check| | |check| | |check| |         |         |
 +--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
 | nearbyintf   | |check| | |check| | |check| | |check| | |check| |         |         | |check| | |check| | |check| |         |         |

libc/spec/stdc.td

@@ -559,6 +559,7 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"nanf", RetValSpec<FloatType>, [ArgSpec<ConstCharPtr>]>,
           FunctionSpec<"nan", RetValSpec<DoubleType>, [ArgSpec<ConstCharPtr>]>,
           FunctionSpec<"nanl", RetValSpec<LongDoubleType>, [ArgSpec<ConstCharPtr>]>,
+          GuardedFunctionSpec<"nanf128", RetValSpec<Float128Type>, [ArgSpec<ConstCharPtr>], "LIBC_TYPES_HAS_FLOAT128">,
       ]
   >;
 

libc/src/__support/UInt.h

@@ -993,6 +993,68 @@ struct is_big_int<BigInt<Bits, Signed, T>> : cpp::true_type {};
 template <class T>
 LIBC_INLINE_VAR constexpr bool is_big_int_v = is_big_int<T>::value;
 
+// extensions of type traits to include BigInt
+
+// is_integral_or_big_int
+template <typename T>
+struct is_integral_or_big_int
+    : cpp::bool_constant<(cpp::is_integral_v<T> || is_big_int_v<T>)> {};
+
+template <typename T>
+LIBC_INLINE_VAR constexpr bool is_integral_or_big_int_v =
+    is_integral_or_big_int<T>::value;
+
+// make_big_int_unsigned
+template <typename T> struct make_big_int_unsigned;
+
+template <size_t Bits, bool Signed, typename T>
+struct make_big_int_unsigned<BigInt<Bits, Signed, T>>
+    : cpp::type_identity<BigInt<Bits, false, T>> {};
+
+template <typename T>
+using make_big_int_unsigned_t = typename make_big_int_unsigned<T>::type;
+
+// make_big_int_signed
+template <typename T> struct make_big_int_signed;
+
+template <size_t Bits, bool Signed, typename T>
+struct make_big_int_signed<BigInt<Bits, Signed, T>>
+    : cpp::type_identity<BigInt<Bits, true, T>> {};
+
+template <typename T>
+using make_big_int_signed_t = typename make_big_int_signed<T>::type;
+
+// make_integral_or_big_int_unsigned
+template <typename T, class = void> struct make_integral_or_big_int_unsigned;
+
+template <typename T>
+struct make_integral_or_big_int_unsigned<
+    T, cpp::enable_if_t<cpp::is_integral_v<T>>> : cpp::make_unsigned<T> {};
+
+template <typename T>
+struct make_integral_or_big_int_unsigned<T, cpp::enable_if_t<is_big_int_v<T>>>
+    : make_big_int_unsigned<T> {};
+
+template <typename T>
+using make_integral_or_big_int_unsigned_t =
+    typename make_integral_or_big_int_unsigned<T>::type;
+
+// make_integral_or_big_int_signed
+template <typename T, class = void> struct make_integral_or_big_int_signed;
+
+template <typename T>
+struct make_integral_or_big_int_signed<T,
+                                       cpp::enable_if_t<cpp::is_integral_v<T>>>
+    : cpp::make_signed<T> {};
+
+template <typename T>
+struct make_integral_or_big_int_signed<T, cpp::enable_if_t<is_big_int_v<T>>>
+    : make_big_int_signed<T> {};
+
+template <typename T>
+using make_integral_or_big_int_signed_t =
+    typename make_integral_or_big_int_signed<T>::type;
+
 namespace cpp {
 
 // Specialization of cpp::bit_cast ('bit.h') from T to BigInt.

libc/src/__support/integer_to_string.h

@@ -67,7 +67,7 @@
 #include "src/__support/CPP/span.h"
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/CPP/type_traits.h"
-#include "src/__support/UInt.h" // is_big_int
+#include "src/__support/UInt.h" // make_integral_or_big_int_unsigned_t
 #include "src/__support/common.h"
 
 namespace LIBC_NAMESPACE {
@@ -150,18 +150,6 @@ template <bool forward> class StringBufferWriterImpl {
 using StringBufferWriter = StringBufferWriterImpl<true>;
 using BackwardStringBufferWriter = StringBufferWriterImpl<false>;
 
-template <typename T, class = void> struct IntegerWriterUnsigned {};
-
-template <typename T>
-struct IntegerWriterUnsigned<T, cpp::enable_if_t<cpp::is_integral_v<T>>> {
-  using type = cpp::make_unsigned_t<T>;
-};
-
-template <typename T>
-struct IntegerWriterUnsigned<T, cpp::enable_if_t<is_big_int_v<T>>> {
-  using type = typename T::unsigned_type;
-};
-
 } // namespace details
 
 namespace radix {
@@ -222,7 +210,7 @@ template <typename T, typename Fmt = radix::Dec> class IntegerToString {
   // An internal stateless structure that handles the number formatting logic.
   struct IntegerWriter {
     static_assert(cpp::is_integral_v<T> || is_big_int_v<T>);
-    using UNSIGNED_T = typename details::IntegerWriterUnsigned<T>::type;
+    using UNSIGNED_T = make_integral_or_big_int_unsigned_t<T>;
 
     LIBC_INLINE static char digit_char(uint8_t digit) {
       if (digit < 10)

libc/src/__support/str_to_float.h

@@ -1056,17 +1056,17 @@ hexadecimal_string_to_float(const char *__restrict src,
   return output;
 }
 
-LIBC_INLINE uint64_t
+template <class T>
+LIBC_INLINE typename fputil::FPBits<T>::StorageType
 nan_mantissa_from_ncharseq(const cpp::string_view ncharseq) {
-  uint64_t nan_mantissa = 0;
+  using FPBits = typename fputil::FPBits<T>;
+  using StorageType = typename FPBits::StorageType;
+
+  StorageType nan_mantissa = 0;
 
   if (ncharseq.data() != nullptr && isdigit(ncharseq[0])) {
-    // This is to prevent errors when StorageType is larger than 64
-    // bits, since strtointeger only supports up to 64 bits. This is
-    // actually more than is required by the specification, which says
-    // for the input type "NAN(n-char-sequence)" that "the meaning of
-    // the n-char sequence is implementation-defined."
-    auto strtoint_result = strtointeger<uint64_t>(ncharseq.data(), 0);
+    StrToNumResult<StorageType> strtoint_result =
+        strtointeger<StorageType>(ncharseq.data(), 0);
     if (!strtoint_result.has_error())
       nan_mantissa = strtoint_result.value;
 
@@ -1172,9 +1172,8 @@ LIBC_INLINE StrToNumResult<T> strtofloatingpoint(const char *__restrict src) {
           ++index;
         if (src[index] == ')') {
           ++index;
-          auto nan_mantissa_result = nan_mantissa_from_ncharseq(
+          nan_mantissa = nan_mantissa_from_ncharseq<T>(
               cpp::string_view(src + (left_paren + 1), index - left_paren - 2));
-          nan_mantissa = static_cast<StorageType>(nan_mantissa_result);
         } else {
           index = left_paren;
         }
@@ -1221,11 +1220,8 @@ template <class T> LIBC_INLINE StrToNumResult<T> strtonan(const char *arg) {
   while (isalnum(arg[index]) || arg[index] == '_')
     ++index;
 
-  if (arg[index] == '\0') {
-    auto nan_mantissa_result =
-        nan_mantissa_from_ncharseq(cpp::string_view(arg, index));
-    nan_mantissa = static_cast<StorageType>(nan_mantissa_result);
-  }
+  if (arg[index] == '\0')
+    nan_mantissa = nan_mantissa_from_ncharseq<T>(cpp::string_view(arg, index));
 
   result = FPBits::quiet_nan(fputil::Sign::POS, nan_mantissa);
   return {result.get_val(), 0, error};

libc/src/__support/str_to_integer.h

@@ -11,6 +11,7 @@
 
 #include "src/__support/CPP/limits.h"
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/UInt128.h"
 #include "src/__support/common.h"
 #include "src/__support/ctype_utils.h"
 #include "src/__support/str_to_num_result.h"
@@ -75,8 +76,12 @@ template <class T>
 LIBC_INLINE StrToNumResult<T>
 strtointeger(const char *__restrict src, int base,
              const size_t src_len = cpp::numeric_limits<size_t>::max()) {
-  // TODO: Rewrite to support numbers longer than long long
-  unsigned long long result = 0;
+  using ResultType = typename cpp::conditional_t<(cpp::is_same_v<T, UInt128> ||
+                                                  cpp::is_same_v<T, Int128>),
+                                                 UInt128, unsigned long long>;
+
+  ResultType result = 0;
+
   bool is_number = false;
   size_t src_cur = 0;
   int error_val = 0;
@@ -101,15 +106,16 @@ strtointeger(const char *__restrict src, int base,
   if (base == 16 && is_hex_start(src + src_cur, src_len - src_cur))
     src_cur = src_cur + 2;
 
-  constexpr bool IS_UNSIGNED = (cpp::numeric_limits<T>::min() == 0);
+  constexpr bool IS_UNSIGNED = cpp::is_unsigned_v<T>;
   const bool is_positive = (result_sign == '+');
-  unsigned long long constexpr NEGATIVE_MAX =
-      !IS_UNSIGNED
-          ? static_cast<unsigned long long>(cpp::numeric_limits<T>::max()) + 1
-          : cpp::numeric_limits<T>::max();
-  unsigned long long const abs_max =
+
+  ResultType constexpr NEGATIVE_MAX =
+      !IS_UNSIGNED ? static_cast<ResultType>(cpp::numeric_limits<T>::max()) + 1
+                   : cpp::numeric_limits<T>::max();
+  ResultType const abs_max =
       (is_positive ? cpp::numeric_limits<T>::max() : NEGATIVE_MAX);
-  unsigned long long const abs_max_div_by_base = abs_max / base;
+  ResultType const abs_max_div_by_base = abs_max / base;
+
   while (src_cur < src_len && isalnum(src[src_cur])) {
     int cur_digit = b36_char_to_int(src[src_cur]);
     if (cur_digit >= base)
@@ -149,10 +155,12 @@ strtointeger(const char *__restrict src, int base,
       return {cpp::numeric_limits<T>::min(), str_len, error_val};
   }
 
-  return {is_positive
-              ? static_cast<T>(result)
-              : static_cast<T>(-static_cast<cpp::make_unsigned_t<T>>(result)),
-          str_len, error_val};
+  return {
+      is_positive
+          ? static_cast<T>(result)
+          : static_cast<T>(
+                -static_cast<make_integral_or_big_int_unsigned_t<T>>(result)),
+      str_len, error_val};
 }
 
 } // namespace internal

libc/src/math/CMakeLists.txt

@@ -190,6 +190,7 @@ add_math_entrypoint_object(modff128)
 add_math_entrypoint_object(nan)
 add_math_entrypoint_object(nanf)
 add_math_entrypoint_object(nanl)
+add_math_entrypoint_object(nanf128)
 
 add_math_entrypoint_object(nearbyint)
 add_math_entrypoint_object(nearbyintf)