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+/*
+ * jquanti-neon.c - sample data conversion and quantization (Arm Neon)
+ *
+ * Copyright (C) 2020-2021, Arm Limited. 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.
+ */
+
+#define JPEG_INTERNALS
+#include "../../jinclude.h"
+#include "../../jpeglib.h"
+#include "../../jsimd.h"
+#include "../../jdct.h"
+#include "../../jsimddct.h"
+#include "../jsimd.h"
+
+#include <arm_neon.h>
+
+
+/* After downsampling, the resulting sample values are in the range [0, 255],
+ * but the Discrete Cosine Transform (DCT) operates on values centered around
+ * 0.
+ *
+ * To prepare sample values for the DCT, load samples into a DCT workspace,
+ * subtracting CENTERJSAMPLE (128). The samples, now in the range [-128, 127],
+ * are also widened from 8- to 16-bit.
+ *
+ * The equivalent scalar C function convsamp() can be found in jcdctmgr.c.
+ */
+
+void jsimd_convsamp_neon(JSAMPARRAY sample_data, JDIMENSION start_col,
+ DCTELEM *workspace)
+{
+ uint8x8_t samp_row0 = vld1_u8(sample_data[0] + start_col);
+ uint8x8_t samp_row1 = vld1_u8(sample_data[1] + start_col);
+ uint8x8_t samp_row2 = vld1_u8(sample_data[2] + start_col);
+ uint8x8_t samp_row3 = vld1_u8(sample_data[3] + start_col);
+ uint8x8_t samp_row4 = vld1_u8(sample_data[4] + start_col);
+ uint8x8_t samp_row5 = vld1_u8(sample_data[5] + start_col);
+ uint8x8_t samp_row6 = vld1_u8(sample_data[6] + start_col);
+ uint8x8_t samp_row7 = vld1_u8(sample_data[7] + start_col);
+
+ int16x8_t row0 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row0, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row1 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row1, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row2 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row2, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row3 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row3, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row4 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row4, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row5 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row5, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row6 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row6, vdup_n_u8(CENTERJSAMPLE)));
+ int16x8_t row7 =
+ vreinterpretq_s16_u16(vsubl_u8(samp_row7, vdup_n_u8(CENTERJSAMPLE)));
+
+ vst1q_s16(workspace + 0 * DCTSIZE, row0);
+ vst1q_s16(workspace + 1 * DCTSIZE, row1);
+ vst1q_s16(workspace + 2 * DCTSIZE, row2);
+ vst1q_s16(workspace + 3 * DCTSIZE, row3);
+ vst1q_s16(workspace + 4 * DCTSIZE, row4);
+ vst1q_s16(workspace + 5 * DCTSIZE, row5);
+ vst1q_s16(workspace + 6 * DCTSIZE, row6);
+ vst1q_s16(workspace + 7 * DCTSIZE, row7);
+}
+
+
+/* After the DCT, the resulting array of coefficient values needs to be divided
+ * by an array of quantization values.
+ *
+ * To avoid a slow division operation, the DCT coefficients are multiplied by
+ * the (scaled) reciprocals of the quantization values and then right-shifted.
+ *
+ * The equivalent scalar C function quantize() can be found in jcdctmgr.c.
+ */
+
+void jsimd_quantize_neon(JCOEFPTR coef_block, DCTELEM *divisors,
+ DCTELEM *workspace)
+{
+ JCOEFPTR out_ptr = coef_block;
+ UDCTELEM *recip_ptr = (UDCTELEM *)divisors;
+ UDCTELEM *corr_ptr = (UDCTELEM *)divisors + DCTSIZE2;
+ DCTELEM *shift_ptr = divisors + 3 * DCTSIZE2;
+ int i;
+
+#if defined(__clang__) && (defined(__aarch64__) || defined(_M_ARM64))
+#pragma unroll
+#endif
+ for (i = 0; i < DCTSIZE; i += DCTSIZE / 2) {
+ /* Load DCT coefficients. */
+ int16x8_t row0 = vld1q_s16(workspace + (i + 0) * DCTSIZE);
+ int16x8_t row1 = vld1q_s16(workspace + (i + 1) * DCTSIZE);
+ int16x8_t row2 = vld1q_s16(workspace + (i + 2) * DCTSIZE);
+ int16x8_t row3 = vld1q_s16(workspace + (i + 3) * DCTSIZE);
+ /* Load reciprocals of quantization values. */
+ uint16x8_t recip0 = vld1q_u16(recip_ptr + (i + 0) * DCTSIZE);
+ uint16x8_t recip1 = vld1q_u16(recip_ptr + (i + 1) * DCTSIZE);
+ uint16x8_t recip2 = vld1q_u16(recip_ptr + (i + 2) * DCTSIZE);
+ uint16x8_t recip3 = vld1q_u16(recip_ptr + (i + 3) * DCTSIZE);
+ uint16x8_t corr0 = vld1q_u16(corr_ptr + (i + 0) * DCTSIZE);
+ uint16x8_t corr1 = vld1q_u16(corr_ptr + (i + 1) * DCTSIZE);
+ uint16x8_t corr2 = vld1q_u16(corr_ptr + (i + 2) * DCTSIZE);
+ uint16x8_t corr3 = vld1q_u16(corr_ptr + (i + 3) * DCTSIZE);
+ int16x8_t shift0 = vld1q_s16(shift_ptr + (i + 0) * DCTSIZE);
+ int16x8_t shift1 = vld1q_s16(shift_ptr + (i + 1) * DCTSIZE);
+ int16x8_t shift2 = vld1q_s16(shift_ptr + (i + 2) * DCTSIZE);
+ int16x8_t shift3 = vld1q_s16(shift_ptr + (i + 3) * DCTSIZE);
+
+ /* Extract sign from coefficients. */
+ int16x8_t sign_row0 = vshrq_n_s16(row0, 15);
+ int16x8_t sign_row1 = vshrq_n_s16(row1, 15);
+ int16x8_t sign_row2 = vshrq_n_s16(row2, 15);
+ int16x8_t sign_row3 = vshrq_n_s16(row3, 15);
+ /* Get absolute value of DCT coefficients. */
+ uint16x8_t abs_row0 = vreinterpretq_u16_s16(vabsq_s16(row0));
+ uint16x8_t abs_row1 = vreinterpretq_u16_s16(vabsq_s16(row1));
+ uint16x8_t abs_row2 = vreinterpretq_u16_s16(vabsq_s16(row2));
+ uint16x8_t abs_row3 = vreinterpretq_u16_s16(vabsq_s16(row3));
+ /* Add correction. */
+ abs_row0 = vaddq_u16(abs_row0, corr0);
+ abs_row1 = vaddq_u16(abs_row1, corr1);
+ abs_row2 = vaddq_u16(abs_row2, corr2);
+ abs_row3 = vaddq_u16(abs_row3, corr3);
+
+ /* Multiply DCT coefficients by quantization reciprocals. */
+ int32x4_t row0_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row0),
+ vget_low_u16(recip0)));
+ int32x4_t row0_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row0),
+ vget_high_u16(recip0)));
+ int32x4_t row1_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row1),
+ vget_low_u16(recip1)));
+ int32x4_t row1_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row1),
+ vget_high_u16(recip1)));
+ int32x4_t row2_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row2),
+ vget_low_u16(recip2)));
+ int32x4_t row2_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row2),
+ vget_high_u16(recip2)));
+ int32x4_t row3_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row3),
+ vget_low_u16(recip3)));
+ int32x4_t row3_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row3),
+ vget_high_u16(recip3)));
+ /* Narrow back to 16-bit. */
+ row0 = vcombine_s16(vshrn_n_s32(row0_l, 16), vshrn_n_s32(row0_h, 16));
+ row1 = vcombine_s16(vshrn_n_s32(row1_l, 16), vshrn_n_s32(row1_h, 16));
+ row2 = vcombine_s16(vshrn_n_s32(row2_l, 16), vshrn_n_s32(row2_h, 16));
+ row3 = vcombine_s16(vshrn_n_s32(row3_l, 16), vshrn_n_s32(row3_h, 16));
+
+ /* Since VSHR only supports an immediate as its second argument, negate the
+ * shift value and shift left.
+ */
+ row0 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row0),
+ vnegq_s16(shift0)));
+ row1 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row1),
+ vnegq_s16(shift1)));
+ row2 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row2),
+ vnegq_s16(shift2)));
+ row3 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row3),
+ vnegq_s16(shift3)));
+
+ /* Restore sign to original product. */
+ row0 = veorq_s16(row0, sign_row0);
+ row0 = vsubq_s16(row0, sign_row0);
+ row1 = veorq_s16(row1, sign_row1);
+ row1 = vsubq_s16(row1, sign_row1);
+ row2 = veorq_s16(row2, sign_row2);
+ row2 = vsubq_s16(row2, sign_row2);
+ row3 = veorq_s16(row3, sign_row3);
+ row3 = vsubq_s16(row3, sign_row3);
+
+ /* Store quantized coefficients to memory. */
+ vst1q_s16(out_ptr + (i + 0) * DCTSIZE, row0);
+ vst1q_s16(out_ptr + (i + 1) * DCTSIZE, row1);
+ vst1q_s16(out_ptr + (i + 2) * DCTSIZE, row2);
+ vst1q_s16(out_ptr + (i + 3) * DCTSIZE, row3);
+ }
+}