From ea489b8b0d89e391455689b7cc397d0c261677c9 Mon Sep 17 00:00:00 2001 From: Andre McCurdy Date: Wed, 18 Apr 2018 17:41:00 -0700 Subject: provide optimized a_ctz_32 for arm Provide an ARM specific a_ctz_32 helper function for architecture versions for which it can be implemented efficiently via the "rbit" instruction (ie all Thumb-2 capable versions of ARM v6 and above). --- arch/arm/atomic_arch.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'arch/arm') diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h index c5c56f81..72fcddb4 100644 --- a/arch/arm/atomic_arch.h +++ b/arch/arm/atomic_arch.h @@ -91,4 +91,16 @@ static inline int a_clz_32(uint32_t x) return x; } +#if __ARM_ARCH_6T2__ || __ARM_ARCH_7A__ || __ARM_ARCH_7R__ || __ARM_ARCH >= 7 + +#define a_ctz_32 a_ctz_32 +static inline int a_ctz_32(uint32_t x) +{ + uint32_t xr; + __asm__ ("rbit %0, %1" : "=r"(xr) : "r"(x)); + return a_clz_32(xr); +} + +#endif + #endif -- cgit v1.2.1