ref: fd8fda9937bbf76d842b91abe05fa393cdaf9c29
dir: /libcelt/entcode.c/
#ifdef HAVE_CONFIG_H #include "config.h" #endif #include "entcode.h" int ec_ilog(ec_uint32 _v){ #if defined(EC_CLZ) return EC_CLZ0-EC_CLZ(_v); #else /*On a Pentium M, this branchless version tested as the fastest on 1,000,000,000 random 32-bit integers, edging out a similar version with branches, and a 256-entry LUT version.*/ int ret; int m; ret=!!_v; m=!!(_v&0xFFFF0000)<<4; _v>>=m; ret|=m; m=!!(_v&0xFF00)<<3; _v>>=m; ret|=m; m=!!(_v&0xF0)<<2; _v>>=m; ret|=m; m=!!(_v&0xC)<<1; _v>>=m; ret|=m; ret+=!!(_v&0x2); return ret; #endif } int ec_ilog64(ec_uint64 _v){ #if defined(EC_CLZ64) return EC_CLZ64_0-EC_CLZ64(_v); #else ec_uint32 v; int ret; int m; ret=!!_v; m=!!(_v&((ec_uint64)0xFFFFFFFF)<<32)<<5; v=(ec_uint32)(_v>>m); ret|=m; m=!!(v&0xFFFF0000)<<4; v>>=m; ret|=m; m=!!(v&0xFF00)<<3; v>>=m; ret|=m; m=!!(v&0xF0)<<2; v>>=m; ret|=m; m=!!(v&0xC)<<1; v>>=m; ret|=m; ret+=!!(v&0x2); return ret; #endif }