In ripn jet, handle zero values correctly.
/*
Divide, rounding up.
*/
-#define DIVCEIL(x,y) 1 + ((x - 1) / y);
+#define DIVCEIL(x,y) \
+ (x==0) ? 0 : \
+ 1 + ((x - 1) / y);
/*
`ripn` breaks `atom` into a list of blocks, of bit-width `bits`. The
