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// Copyright (c) 2008-2020 NVIDIA Corporation. All rights reserved.
// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.

#pragma once

#if PX_GCC_FAMILY ||  NV_ORBIS
#include <xmmintrin.h> // _BitScanForward
#else
#if __APPLE__
#include <x86intrin.h>
#else
#pragma warning(push)
#pragma warning(disable : 4668) //'symbol'  is not defined as a preprocessor macro, replacing with '0' for 'directives'
#pragma warning(disable : 4987) // nonstandard extension used: 'throw (...)'
#pragma warning(pop)
#include <intrin.h>             // _BitScanForward
#endif
#endif

namespace nv
{
namespace cloth
{

uint32_t findBitSet(uint32_t mask)
{
#if defined(_MSC_VER)
	unsigned long result;
	_BitScanForward(&result, unsigned long(mask));
	return result;
#else
	return __builtin_ffs(mask) - 1;
#endif
}

Simd4i intFloor(const Simd4f& v)
{
	Simd4i i = _mm_cvttps_epi32(v);
	return _mm_sub_epi32(i, _mm_srli_epi32(simd4i(v), 31));
	//Simd4i i = truncate(v);
	//return i - (simd4i(v) >> 31);
}

Simd4i horizontalOr(const Simd4i& mask)
{
	Simd4i tmp = mask | _mm_shuffle_epi32(mask, 0xb1); // w z y x -> z w x y
	return tmp | _mm_shuffle_epi32(tmp, 0x4e);         // w z y x -> y x w z
//	return splat<0>(mask) | splat<1>(mask) | splat<2>(mask) | splat<3>(mask);
}

Gather<Simd4i>::Gather(const Simd4i& index)
{
	//index are grid positions
	//grid has 8 spaces, grid indices that are within rage use 3 bits (0x7 mask)
	mSelectQ = _mm_srai_epi32(index << 29, 31); //expand bit 0x4 to the whole register
	mSelectD = _mm_srai_epi32(index << 30, 31); //expand bit 0x2 to the whole register
	mSelectW = _mm_srai_epi32(index << 31, 31); //expand the least significant bit (0x1) to the whole register
	mOutOfRange = (index ^ sIntSignBit) > sSignedMask; //true if index is outside the grid = (index > 0x7 || index < 0x0)
}

Simd4i Gather<Simd4i>::operator()(const Simd4i* ptr) const
{
	//ptr points to the cone/sphere grid

	// more efficient with _mm_shuffle_epi8 (SSSE3)

	//lo contains the bottom 4 grid cells, heigh the top 4
	Simd4i lo = ptr[0], hi = ptr[1];

	//select correct cell in the grid using binary decision tree
	//      m  =         select ?     a        :    b
	//first bit (even/uneven cells)
	Simd4i m01 = select(mSelectW, splat<1>(lo), splat<0>(lo));
	Simd4i m23 = select(mSelectW, splat<3>(lo), splat<2>(lo));
	Simd4i m45 = select(mSelectW, splat<1>(hi), splat<0>(hi));
	Simd4i m67 = select(mSelectW, splat<3>(hi), splat<2>(hi));

	//second bit
	Simd4i m0123 = select(mSelectD, m23, m01);
	Simd4i m4567 = select(mSelectD, m67, m45);

	// third bit							force result zero if it is out of range
	return select(mSelectQ, m4567, m0123) & ~mOutOfRange;
}

} // namespace cloth
} // namespace nv