/*
 * AltiVec optimizations for libjpeg-turbo
 *
 * Copyright (C) 2015, D. R. Commander.  All Rights Reserved.
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

/* This file is included by jdcolor-altivec.c */


void jsimd_ycc_rgb_convert_altivec(JDIMENSION out_width, JSAMPIMAGE input_buf,
                                   JDIMENSION input_row,
                                   JSAMPARRAY output_buf, int num_rows) {
	JSAMPROW outptr, inptr0, inptr1, inptr2;
	int pitch = out_width * RGB_PIXELSIZE, num_cols;
#if __BIG_ENDIAN__
	int offset;
#endif
	unsigned char __attribute__((aligned(16))) tmpbuf[RGB_PIXELSIZE * 16];

	__vector unsigned char rgb0, rgb1, rgb2, rgbx0, rgbx1, rgbx2, rgbx3,
			y, cb, cr;
#if __BIG_ENDIAN__
	__vector unsigned char edgel, edgeh, edges, out0, out1, out2, out3;
#if RGB_PIXELSIZE == 4
	__vector unsigned char out4;
#endif
#endif
#if RGB_PIXELSIZE == 4
	__vector unsigned char rgb3;
#endif
	__vector short rg0, rg1, rg2, rg3, bx0, bx1, bx2, bx3, yl, yh, cbl, cbh,
			crl, crh, rl, rh, gl, gh, bl, bh, g0w, g1w, g2w, g3w;
	__vector int g0, g1, g2, g3;

	/* Constants
	 * NOTE: The >> 1 is to compensate for the fact that vec_madds() returns 17
	 * high-order bits, not 16.
	 */
	__vector short pw_f0402 = {__8X(F_0_402 >> 1)},
			pw_mf0228 = {__8X(-F_0_228 >> 1)},
			pw_mf0344_f0285 = {__4X2(-F_0_344, F_0_285)},
			pw_one = {__8X(1)}, pw_255 = {__8X(255)},
			pw_cj = {__8X(CENTERJSAMPLE)};
	__vector int pd_onehalf = {__4X(ONE_HALF)};
	__vector unsigned char pb_zero = {__16X(0)},
#if __BIG_ENDIAN__
	shift_pack_index = {0,1,4,5,8,9,12,13,16,17,20,21,24,25,28,29};
#else
			shift_pack_index = {2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22, 23, 26, 27, 30, 31};
#endif

	while (--num_rows >= 0) {
		inptr0 = input_buf[0][input_row];
		inptr1 = input_buf[1][input_row];
		inptr2 = input_buf[2][input_row];
		input_row++;
		outptr = *output_buf++;

		for (num_cols = pitch; num_cols > 0;
		     num_cols -= RGB_PIXELSIZE * 16, outptr += RGB_PIXELSIZE * 16,
		     inptr0 += 16, inptr1 += 16, inptr2 += 16) {

			y = vec_ld(0, inptr0);
			/* NOTE: We have to use vec_merge*() here because vec_unpack*() doesn't
			 * support unsigned vectors.
			 */
			yl = (__vector signed short) VEC_UNPACKHU(y);
			yh = (__vector signed short) VEC_UNPACKLU(y);

			cb = vec_ld(0, inptr1);
			cbl = (__vector signed short) VEC_UNPACKHU(cb);
			cbh = (__vector signed short) VEC_UNPACKLU(cb);
			cbl = vec_sub(cbl, pw_cj);
			cbh = vec_sub(cbh, pw_cj);

			cr = vec_ld(0, inptr2);
			crl = (__vector signed short) VEC_UNPACKHU(cr);
			crh = (__vector signed short) VEC_UNPACKLU(cr);
			crl = vec_sub(crl, pw_cj);
			crh = vec_sub(crh, pw_cj);

			/* (Original)
			 * R = Y                + 1.40200 * Cr
			 * G = Y - 0.34414 * Cb - 0.71414 * Cr
			 * B = Y + 1.77200 * Cb
			 *
			 * (This implementation)
			 * R = Y                + 0.40200 * Cr + Cr
			 * G = Y - 0.34414 * Cb + 0.28586 * Cr - Cr
			 * B = Y - 0.22800 * Cb + Cb + Cb
			 */
			bl = vec_add(cbl, cbl);
			bh = vec_add(cbh, cbh);
			bl = vec_madds(bl, pw_mf0228, pw_one);
			bh = vec_madds(bh, pw_mf0228, pw_one);
			bl = vec_sra(bl, (__vector unsigned short) pw_one);
			bh = vec_sra(bh, (__vector unsigned short) pw_one);
			bl = vec_add(bl, cbl);
			bh = vec_add(bh, cbh);
			bl = vec_add(bl, cbl);
			bh = vec_add(bh, cbh);
			bl = vec_add(bl, yl);
			bh = vec_add(bh, yh);

			rl = vec_add(crl, crl);
			rh = vec_add(crh, crh);
			rl = vec_madds(rl, pw_f0402, pw_one);
			rh = vec_madds(rh, pw_f0402, pw_one);
			rl = vec_sra(rl, (__vector unsigned short) pw_one);
			rh = vec_sra(rh, (__vector unsigned short) pw_one);
			rl = vec_add(rl, crl);
			rh = vec_add(rh, crh);
			rl = vec_add(rl, yl);
			rh = vec_add(rh, yh);

			g0w = vec_mergeh(cbl, crl);
			g1w = vec_mergel(cbl, crl);
			g0 = vec_msums(g0w, pw_mf0344_f0285, pd_onehalf);
			g1 = vec_msums(g1w, pw_mf0344_f0285, pd_onehalf);
			g2w = vec_mergeh(cbh, crh);
			g3w = vec_mergel(cbh, crh);
			g2 = vec_msums(g2w, pw_mf0344_f0285, pd_onehalf);
			g3 = vec_msums(g3w, pw_mf0344_f0285, pd_onehalf);
			/* Clever way to avoid 4 shifts + 2 packs.  This packs the high word from
			 * each dword into a new 16-bit vector, which is the equivalent of
			 * descaling the 32-bit results (right-shifting by 16 bits) and then
			 * packing them.
			 */
			gl = vec_perm((__vector short) g0, (__vector short) g1, shift_pack_index);
			gh = vec_perm((__vector short) g2, (__vector short) g3, shift_pack_index);
			gl = vec_sub(gl, crl);
			gh = vec_sub(gh, crh);
			gl = vec_add(gl, yl);
			gh = vec_add(gh, yh);

			rg0 = vec_mergeh(rl, gl);
			bx0 = vec_mergeh(bl, pw_255);
			rg1 = vec_mergel(rl, gl);
			bx1 = vec_mergel(bl, pw_255);
			rg2 = vec_mergeh(rh, gh);
			bx2 = vec_mergeh(bh, pw_255);
			rg3 = vec_mergel(rh, gh);
			bx3 = vec_mergel(bh, pw_255);

			rgbx0 = vec_packsu(rg0, bx0);
			rgbx1 = vec_packsu(rg1, bx1);
			rgbx2 = vec_packsu(rg2, bx2);
			rgbx3 = vec_packsu(rg3, bx3);

#if RGB_PIXELSIZE == 3
			/* rgbx0 = R0 G0 R1 G1 R2 G2 R3 G3 B0 X0 B1 X1 B2 X2 B3 X3
			 * rgbx1 = R4 G4 R5 G5 R6 G6 R7 G7 B4 X4 B5 X5 B6 X6 B7 X7
			 * rgbx2 = R8 G8 R9 G9 Ra Ga Rb Gb B8 X8 B9 X9 Ba Xa Bb Xb
			 * rgbx3 = Rc Gc Rd Gd Re Ge Rf Gf Bc Xc Bd Xd Be Xe Bf Xf
			 *
			 * rgb0 = R0 G0 B0 R1 G1 B1 R2 G2 B2 R3 G3 B3 R4 G4 B4 R5
			 * rgb1 = G5 B5 R6 G6 B6 R7 G7 B7 R8 G8 B8 R9 G9 B9 Ra Ga
			 * rgb2 = Ba Rb Gb Bb Rc Gc Bc Rd Gd Bd Re Ge Be Rf Gf Bf
			 */
			rgb0 = vec_perm(rgbx0, rgbx1, (__vector unsigned char)RGB_INDEX0);
			rgb1 = vec_perm(rgbx1, rgbx2, (__vector unsigned char)RGB_INDEX1);
			rgb2 = vec_perm(rgbx2, rgbx3, (__vector unsigned char)RGB_INDEX2);
#else
			/* rgbx0 = R0 G0 R1 G1 R2 G2 R3 G3 B0 X0 B1 X1 B2 X2 B3 X3
			 * rgbx1 = R4 G4 R5 G5 R6 G6 R7 G7 B4 X4 B5 X5 B6 X6 B7 X7
			 * rgbx2 = R8 G8 R9 G9 Ra Ga Rb Gb B8 X8 B9 X9 Ba Xa Bb Xb
			 * rgbx3 = Rc Gc Rd Gd Re Ge Rf Gf Bc Xc Bd Xd Be Xe Bf Xf
			 *
			 * rgb0 = R0 G0 B0 X0 R1 G1 B1 X1 R2 G2 B2 X2 R3 G3 B3 X3
			 * rgb1 = R4 G4 B4 X4 R5 G5 B5 X5 R6 G6 B6 X6 R7 G7 B7 X7
			 * rgb2 = R8 G8 B8 X8 R9 G9 B9 X9 Ra Ga Ba Xa Rb Gb Bb Xb
			 * rgb3 = Rc Gc Bc Xc Rd Gd Bd Xd Re Ge Be Xe Rf Gf Bf Xf
			 */
			rgb0 = vec_perm(rgbx0, rgbx0, (__vector unsigned char) RGB_INDEX);
			rgb1 = vec_perm(rgbx1, rgbx1, (__vector unsigned char) RGB_INDEX);
			rgb2 = vec_perm(rgbx2, rgbx2, (__vector unsigned char) RGB_INDEX);
			rgb3 = vec_perm(rgbx3, rgbx3, (__vector unsigned char) RGB_INDEX);
#endif

#if __BIG_ENDIAN__
			offset = (size_t)outptr & 15;
			if (offset) {
			  __vector unsigned char unaligned_shift_index;
			  int bytes = num_cols + offset;

			  if (bytes < (RGB_PIXELSIZE + 1) * 16 && (bytes & 15)) {
				/* Slow path to prevent buffer overwrite.  Since there is no way to
				 * write a partial AltiVec register, overwrite would occur on the
				 * last chunk of the last image row if the right edge is not on a
				 * 16-byte boundary.  It could also occur on other rows if the bytes
				 * per row is low enough.  Since we can't determine whether we're on
				 * the last image row, we have to assume every row is the last.
				 */
				vec_st(rgb0, 0, tmpbuf);
				vec_st(rgb1, 16, tmpbuf);
				vec_st(rgb2, 32, tmpbuf);
#if RGB_PIXELSIZE == 4
				vec_st(rgb3, 48, tmpbuf);
#endif
				memcpy(outptr, tmpbuf, min(num_cols, RGB_PIXELSIZE * 16));
			  } else {
				/* Fast path */
				unaligned_shift_index = vec_lvsl(0, outptr);
				edgel = vec_ld(0, outptr);
				edgeh = vec_ld(min(num_cols - 1, RGB_PIXELSIZE * 16), outptr);
				edges = vec_perm(edgeh, edgel, unaligned_shift_index);
				unaligned_shift_index = vec_lvsr(0, outptr);
				out0 = vec_perm(edges, rgb0, unaligned_shift_index);
				out1 = vec_perm(rgb0, rgb1, unaligned_shift_index);
				out2 = vec_perm(rgb1, rgb2, unaligned_shift_index);
#if RGB_PIXELSIZE == 4
				out3 = vec_perm(rgb2, rgb3, unaligned_shift_index);
				out4 = vec_perm(rgb3, edges, unaligned_shift_index);
#else
				out3 = vec_perm(rgb2, edges, unaligned_shift_index);
#endif
				vec_st(out0, 0, outptr);
				if (bytes > 16)
				  vec_st(out1, 16, outptr);
				if (bytes > 32)
				  vec_st(out2, 32, outptr);
				if (bytes > 48)
				  vec_st(out3, 48, outptr);
#if RGB_PIXELSIZE == 4
				if (bytes > 64)
				  vec_st(out4, 64, outptr);
#endif
			  }
			} else {
#endif /* __BIG_ENDIAN__ */
			if (num_cols < RGB_PIXELSIZE * 16 && (num_cols & 15)) {
				/* Slow path */
				VEC_ST(rgb0, 0, tmpbuf);
				VEC_ST(rgb1, 16, tmpbuf);
				VEC_ST(rgb2, 32, tmpbuf);
#if RGB_PIXELSIZE == 4
				VEC_ST(rgb3, 48, tmpbuf);
#endif
				memcpy(outptr, tmpbuf, min(num_cols, RGB_PIXELSIZE * 16));
			} else {
				/* Fast path */
				VEC_ST(rgb0, 0, outptr);
				if (num_cols > 16)
					VEC_ST(rgb1, 16, outptr);
				if (num_cols > 32)
					VEC_ST(rgb2, 32, outptr);
#if RGB_PIXELSIZE == 4
				if (num_cols > 48)
				  VEC_ST(rgb3, 48, outptr);
#endif
			}
#if __BIG_ENDIAN__
			}
#endif
		}
	}
}
