[libc-commits] [libc] [libc][math][c23] Add atanhf16 C23 math function. (PR #132612)

[via libc-commits]

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@@ -297,6 +297,49 @@ LIBC_INLINE static double log2_eval(double x) {
   return result;
 }
 
+// x should be positive, normal finite value
+// TODO: Simplify range reduction and polynomial degree for float16.
+//       See issue #137190.
+LIBC_INLINE static float log_eval_f(float x) {
+  // For x = 2^ex * (1 + mx), logf(x) = ex * logf(2) + logf(1 + mx).
+  using FPBits = fputil::FPBits<float>;
+  FPBits xbits(x);
+
+  float ex = static_cast<float>(xbits.get_exponent());
+  // p1 is the leading 7 bits of mx, i.e.
+  // p1 * 2^(-7) <= m_x < (p1 + 1) * 2^(-7).
+  int p1 = static_cast<int>(xbits.get_mantissa() >> (FPBits::FRACTION_LEN - 7));
+
+  // Set bs to (1 + (mx - p1*2^(-7))
----------------
overmighty wrote:

```suggestion
  // Set bits to (1 + (mx - p1*2^(-7)))
```

https://github.com/llvm/llvm-project/pull/132612