Update docs

Author: totalspectrum

doc/c.md

@@ -474,6 +474,20 @@ x = __builtin_muluh(a, b)
 ```
 Calculates the upper 32 bits of the 64 bit product of (unsigned) integers `a` and `b`.
 
+### MULDIV64
+
+```
+x = _muldiv64(a, b, d)
+```
+Takes three 32 bit unsigned values. Calculates the 64 bit result `a * b`, then divides by `d`.
+
+### ONES
+
+```
+x = _ones(y)
+```
+Counts the number of bits set in the 32 bit integer `y`.
+
 ### PARITY
 
 ```

include/propeller2.h

@@ -142,6 +142,8 @@ uint32_t  _rnd(void);
 int       _clz(uint32_t val);   /* count leading zeros */
 int       _encod(uint32_t val); /* Spin encode operator */
 uint32_t  _isqrt(uint32_t val); /* Spin integer square root */
+uint32_t  _muldiv64(uint32_t m1, uint32_t m2, uint32_t d); /* calculate m1*m2 / d */
+uint32_t  _ones(uint32_t n);    /* count one bits set */
 
 /* counter related functions */
 uint32_t  _cnt(void);