[libc] [llvm] [libc][NFC] Refactor FPBits and remove LongDoubleBits specialization (PR #78192)

[Clement Courbet via llvm-commits]

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@@ -241,6 +294,79 @@ template <FPType fp_type> struct FPRep : public FPRepBase<fp_type> {
   using UP::FRACTION_LEN;
   using UP::FRACTION_MASK;
   using UP::MANTISSA_PRECISION;
+
+protected:
+  using typename UP::Exp;
+  using typename UP::Sig;
+  using UP::encode;
+  using UP::exp_bits;
+  using UP::exp_sig_bits;
+  using UP::sig_bits;
+
+public:
+  LIBC_INLINE constexpr bool is_nan() const {
+    return exp_sig_bits() > encode(Exp::BITS_ALL_ONES, Sig::BITS_ALL_ZEROES);
+  }
+  LIBC_INLINE constexpr bool is_quiet_nan() const {
+    return exp_sig_bits() >= encode(Exp::BITS_ALL_ONES, Sig::MSB);
+  }
+  LIBC_INLINE constexpr bool is_signaling_nan() const {
+    return is_nan() && !is_quiet_nan();
+  }
+  LIBC_INLINE constexpr bool is_inf() const {
+    return exp_sig_bits() == encode(Exp::BITS_ALL_ONES, Sig::BITS_ALL_ZEROES);
+  }
+  LIBC_INLINE constexpr bool is_zero() const {
+    return exp_sig_bits() == encode(Exp::BITS_ALL_ZEROES, Sig::BITS_ALL_ZEROES);
+  }
+  LIBC_INLINE constexpr bool is_finite() const {
+    return exp_bits() != encode(Exp::BITS_ALL_ONES);
+  }
+  LIBC_INLINE
+  constexpr bool is_subnormal() const {
+    return exp_bits() == encode(Exp::BITS_ALL_ZEROES);
+  }
+  LIBC_INLINE constexpr bool is_normal() const {
+    return is_finite() && !is_subnormal();
+  }
+
+  LIBC_INLINE static constexpr StorageType zero(bool sign = false) {
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legrosbuffle wrote:

[nit, maybe in a different patch] What about making `sign` an enum ? I remember not too long ago that a bool parameter meant "toggle the sign". Maybe `enum class Signum { POSITIVE, NEGATIVE }` ?

https://github.com/llvm/llvm-project/pull/78192