From 06fbefd10046a0fae7e588b7c6d25fb51811b931 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Wed, 19 Apr 2017 00:20:54 +0200 Subject: add a_clz_64 helper function counts leading zero bits of a 64bit int, undefined on zero input. (has nothing to do with atomics, added to atomic.h so target specific helper functions are together.) there is a logarithmic generic implementation and another in terms of a 32bit a_clz_32 on targets where that's available. --- src/internal/atomic.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'src/internal/atomic.h') diff --git a/src/internal/atomic.h b/src/internal/atomic.h index 6f37d252..ab473dd7 100644 --- a/src/internal/atomic.h +++ b/src/internal/atomic.h @@ -277,6 +277,27 @@ static inline int a_ctz_64(uint64_t x) } #endif +#ifndef a_clz_64 +#define a_clz_64 a_clz_64 +static inline int a_clz_64(uint64_t x) +{ +#ifdef a_clz_32 + if (x>>32) + return a_clz_32(x>>32); + return a_clz_32(x) + 32; +#else + uint32_t y; + int r; + if (x>>32) y=x>>32, r=0; else y=x, r=32; + if (y>>16) y>>=16; else r |= 16; + if (y>>8) y>>=8; else r |= 8; + if (y>>4) y>>=4; else r |= 4; + if (y>>2) y>>=2; else r |= 2; + return r | !(y>>1); +#endif +} +#endif + #ifndef a_ctz_l #define a_ctz_l a_ctz_l static inline int a_ctz_l(unsigned long x) -- cgit v1.2.1