[libc][NFC] Rename `MANTISSA_WIDTH` in `FRACTION_LEN` (#75489)

This one might be a bit controversial since the terminology has been
introduced from the start but I think `FRACTION_LEN` is a better name
here. AFAICT it really is "the number of bits after the decimal dot when
the number is in normal form."

`MANTISSA_WIDTH` is less precise as it's unclear whether we take the
leading bit into account.
This patch also renames most of the properties to use the `_LEN` suffix
and fixes useless casts or variables.

1 files changed, 1 insertions, 1 deletions

diff --git a/libc/src/math/generic/log1pf.cpp b/libc/src/math/generic/log1pf.cpp
index fabd2bdc31bf..891700d5ed08 100644
--- a/libc/src/math/generic/log1pf.cpp
+++ b/libc/src/math/generic/log1pf.cpp
@@ -57,7 +57,7 @@ LIBC_INLINE float log(double x) {
   // Get the 8 highest bits, use 7 bits (excluding the implicit hidden bit) for
   // lookup tables.
   int f_index = static_cast<int>(xbits.get_mantissa() >>
-                                 (fputil::FPBits<double>::MANTISSA_WIDTH - 7));
+                                 (fputil::FPBits<double>::FRACTION_LEN - 7));
 
   // Set bits to 1.m
   xbits.set_biased_exponent(0x3FF);