ref: dfa24594cbd5c2e8dee253abf7bd04edc3bb0612
dir: /src/plan9_builtins.c/
int __builtin_ctz(unsigned int x) { unsigned int r; if(x == 0) return 32; for(r = 0; (x & 1) == 0; x >>= 1, r++); return r; } int __builtin_clz(unsigned int x) { unsigned int r; if(x == 0) return 32; for(r = 0; (x & (1UL<<31)) == 0; x <<= 1, r++); return r; } int __builtin_clzll(unsigned long long x) { unsigned long long r; if(x == 0) return 64; for(r = 0; (x & (1ULL<<63)) == 0; x <<= 1, r++); return r; }