animetosho

Count Leading/Trailing Zero Bits (Byte-wise)

Counting the trailing zero bit count (TZCNT) can be done by isolating the lowest bit, then depositing this into the appropriate locations for the count. The leading zero bit count (LZCNT) can be done by reversing bits, then computing the TZCNT.

__m128i _mm_tzcnt_epi8(__m128i a) {
	// isolate lowest bit
	a = _mm_andnot_si128(_mm_add_epi8(a, _mm_set1_epi8(0xff)), a);
	// convert lowest bit to index

jibsen

About

These are timings for cloning the [squash][] repository including submodules, running [CMake][] to generate makefiles, and building the project in debug mode.

All toolsets run on the same machine (Core i5, 8 GB, Win10 64):

panzi

// "License": Public Domain
// I, Mathias Panzenböck, place this file hereby into the public domain. Use it at your own risk for whatever you like.
// In case there are jurisdictions that don't support putting things in the public domain you can also consider it to
// be "dual licensed" under the BSD, MIT and Apache licenses, if you want to. This code is trivial anyway. Consider it
// an example on how to get the endian conversion functions on different platforms.

#ifndef PORTABLE_ENDIAN_H__
#define PORTABLE_ENDIAN_H__

#if (defined(_WIN16) || defined(_WIN32) || defined(_WIN64)) && !defined(__WINDOWS__)