avir_float8_avx.h

//$ nobt
//$ nocpp

/**
 * @file avir_float8_avx.h
 *
 * @brief Inclusion file for the "float8" type.
 *
 * This file includes the "float8" AVX-based type used for SIMD variable
 * storage and processing.
 *
 * AVIR Copyright (c) 2015 Aleksey Vaneev
 */

#ifndef AVIR_FLOAT8_AVX_INCLUDED
#define AVIR_FLOAT8_AVX_INCLUDED

#include <immintrin.h>
#include "avir_dil.h"

namespace avir {

/**
 * @brief SIMD packed 8-float type.
 *
 * This class implements a packed 8-float type that can be used to perform
 * parallel computation using SIMD instructions on AVX-enabled processors.
 * This class can be used as the "fptype" argument of the avir::fpclass_def
 * or avir::fpclass_def_dil class.
 */

class float8
{
public:
	float8()
	{
	}

	float8( const float8& s )
		: value( s.value )
	{
	}

	float8( const __m256 s )
		: value( s )
	{
	}

	float8( const float s )
		: value( _mm256_set1_ps( s ))
	{
	}

	float8& operator = ( const float8& s )
	{
		value = s.value;
		return( *this );
	}

	float8& operator = ( const __m256 s )
	{
		value = s;
		return( *this );
	}

	float8& operator = ( const float s )
	{
		value = _mm256_set1_ps( s );
		return( *this );
	}

	operator float () const
	{
		return( _mm_cvtss_f32( _mm256_extractf128_ps( value, 0 )));
	}

	/**
	 * @param p Pointer to memory from where the value should be loaded,
	 * should be 16-byte aligned.
	 * @return float8 value loaded from the specified memory location.
	 */

	static float8 load( const float* const p )
	{
		return( _mm256_load_ps( p ));
	}

	/**
	 * @param p Pointer to memory from where the value should be loaded,
	 * may have any alignment.
	 * @return float8 value loaded from the specified memory location.
	 */

	static float8 loadu( const float* const p )
	{
		return( _mm256_loadu_ps( p ));
	}

	/**
	 * @param p Pointer to memory from where the value should be loaded,
	 * may have any alignment.
	 * @param lim The maximum number of elements to load, >0.
	 * @return float8 value loaded from the specified memory location, with
	 * elements beyond "lim" set to 0.
	 */

	static float8 loadu( const float* const p, const int lim )
	{
		__m128 lo;
		__m128 hi;

		if( lim > 4 )
		{
			lo = _mm_loadu_ps( p );
			hi = loadu4( p + 4, lim - 4 );
		}
		else
		{
			lo = loadu4( p, lim );
			hi = _mm_setzero_ps();
		}

		return( _mm256_insertf128_ps( _mm256_castps128_ps256( lo ), hi, 1 ));
	}

	/**
	 * Function stores *this value to the specified memory location.
	 *
	 * @param[out] p Output memory location, may have any alignment.
	 */

	void storeu( float* const p ) const
	{
		_mm256_storeu_ps( p, value );
	}

	/**
	 * Function stores "lim" lower elements of *this value to the specified
	 * memory location.
	 *
	 * @param[out] p Output memory location, may have any alignment.
	 * @param lim The number of lower elements to store, >0.
	 */

	void storeu( float* p, int lim ) const
	{
		__m128 v;

		if( lim > 4 )
		{
			_mm_storeu_ps( p, _mm256_extractf128_ps( value, 0 ));
			v = _mm256_extractf128_ps( value, 1 );
			p += 4;
			lim -= 4;
		}
		else
		{
			v = _mm256_extractf128_ps( value, 0 );
		}

		if( lim > 2 )
		{
			if( lim > 3 )
			{
				_mm_storeu_ps( p, v );
			}
			else
			{
				_mm_storel_pi( (__m64*) p, v );
				_mm_store_ss( p + 2, _mm_movehl_ps( v, v ));
			}
		}
		else
		{
			if( lim == 2 )
			{
				_mm_storel_pi( (__m64*) p, v );
			}
			else
			{
				_mm_store_ss( p, v );
			}
		}
	}

	float8& operator += ( const float8& s )
	{
		value = _mm256_add_ps( value, s.value );
		return( *this );
	}

	float8& operator -= ( const float8& s )
	{
		value = _mm256_sub_ps( value, s.value );
		return( *this );
	}

	float8& operator *= ( const float8& s )
	{
		value = _mm256_mul_ps( value, s.value );
		return( *this );
	}

	float8& operator /= ( const float8& s )
	{
		value = _mm256_div_ps( value, s.value );
		return( *this );
	}

	float8 operator + ( const float8& s ) const
	{
		return( _mm256_add_ps( value, s.value ));
	}

	float8 operator - ( const float8& s ) const
	{
		return( _mm256_sub_ps( value, s.value ));
	}

	float8 operator * ( const float8& s ) const
	{
		return( _mm256_mul_ps( value, s.value ));
	}

	float8 operator / ( const float8& s ) const
	{
		return( _mm256_div_ps( value, s.value ));
	}

	/**
	 * @return Horizontal sum of elements.
	 */

	float hadd() const
	{
		__m128 v = _mm_add_ps( _mm256_extractf128_ps( value, 0 ),
			_mm256_extractf128_ps( value, 1 ));

		v = _mm_hadd_ps( v, v );
		v = _mm_hadd_ps( v, v );
		return( _mm_cvtss_f32( v ));
	}

	/**
	 * Function performs in-place addition of a value located in memory and
	 * the specified value.
	 *
	 * @param p Pointer to value where addition happens. May be unaligned.
	 * @param v Value to add.
	 */

	static void addu( float* const p, const float8& v )
	{
		( loadu( p ) + v ).storeu( p );
	}

	/**
	 * Function performs in-place addition of a value located in memory and
	 * the specified value. Limited to the specfied number of elements.
	 *
	 * @param p Pointer to value where addition happens. May be unaligned.
	 * @param v Value to add.
	 * @param lim The element number limit, >0.
	 */

	static void addu( float* const p, const float8& v, const int lim )
	{
		( loadu( p, lim ) + v ).storeu( p, lim );
	}

	__m256 value; ///< Packed value of 8 floats.
		///<

private:
	static __m128 loadu4( const float* const p, const int lim )
	{
		if( lim > 2 )
		{
			if( lim > 3 )
			{
				return( _mm_loadu_ps( p ));
			}
			else
			{
				return( _mm_set_ps( 0.0f, p[ 2 ], p[ 1 ], p[ 0 ]));
			}
		}
		else
		{
			if( lim == 2 )
			{
				return( _mm_set_ps( 0.0f, 0.0f, p[ 1 ], p[ 0 ]));
			}
			else
			{
				return( _mm_load_ss( p ));
			}
		}
	}
};

/**
 * SIMD rounding function, exact result.
 *
 * @param v Value to round.
 * @return Rounded SIMD value.
 */

inline float8 round( const float8& v )
{
	return( _mm256_round_ps( v.value,
		( _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC )));
}

/**
 * SIMD function "clamps" (clips) the specified packed values so that they are
 * not lesser than "minv", and not greater than "maxv".
 *
 * @param Value Value to clamp.
 * @param minv Minimal allowed value.
 * @param maxv Maximal allowed value.
 * @return The clamped value.
 */

inline float8 clamp( const float8& Value, const float8 minv,
	const float8 maxv )
{
	return( _mm256_min_ps( _mm256_max_ps( Value.value, minv.value ),
		maxv.value ));
}

template<>
struct fpclass_reset< float8 >
{
	static void reset()
	{
		_mm_empty();
	}
};

template<>
struct fpclass_reset< const float8 >
{
	static void reset()
	{
		_mm_empty();
	}
};

typedef fpclass_def_dil< float, avir :: float8 > fpclass_float8_dil; ///<
	///< Class that can be used as the "fpclass" template parameter of the
	///< avir::CImageResizer class to perform calculation using
	///< de-interleaved SIMD algorithm, using SIMD float8 type.
	///<

} // namespace avir

#endif // AVIR_FLOAT8_AVX_INCLUDED