Implementation of some string.h function using SSE2 instructions
Wojciech Muła
wojciech_mula@poczta.onet.pl
Wed Aug 8 20:19:00 GMT 2007
PaweÂł Sikora wrote:
> {
> __m128i m1 = *( __m128i* )( s1 );
> __m128i m2 = *( __m128i* )( s2 );
> __m128i r1 = not( _mm_cmpeq_epi8( m1, m2 ) );
> __m128i zero = { 0 };
> __m128i r2 = _mm_cmpeq_epi8( m1, zero );
> __m128i r3 = _mm_cmpeq_epi8( m2, zero );
> __m128i r = _mm_or_si128( r1, _mm_or_si128( r2, r3 ) );
> mask = _mm_movemask_epi8( r );
> if ( mask )
> {
> unsigned index = __builtin_ffs( mask ) - 1;
> return ( s1[ index ] - s2[ index ] );
> }
> }
BTW r3 isn't needed.
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