/* * jidctint-neon.c - accurate integer IDCT (Arm Neon) * * Copyright (C) 2020, Arm Limited. All Rights Reserved. * Copyright (C) 2020, 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. */ #define JPEG_INTERNALS #include "../../jinclude.h" #include "../../jpeglib.h" #include "../../jsimd.h" #include "../../jdct.h" #include "../../jsimddct.h" #include "../jsimd.h" #include "align.h" #include "neon-compat.h" #include #define CONST_BITS 13 #define PASS1_BITS 2 #define DESCALE_P1 (CONST_BITS - PASS1_BITS) #define DESCALE_P2 (CONST_BITS + PASS1_BITS + 3) /* The computation of the inverse DCT requires the use of constants known at * compile time. Scaled integer constants are used to avoid floating-point * arithmetic: * 0.298631336 = 2446 * 2^-13 * 0.390180644 = 3196 * 2^-13 * 0.541196100 = 4433 * 2^-13 * 0.765366865 = 6270 * 2^-13 * 0.899976223 = 7373 * 2^-13 * 1.175875602 = 9633 * 2^-13 * 1.501321110 = 12299 * 2^-13 * 1.847759065 = 15137 * 2^-13 * 1.961570560 = 16069 * 2^-13 * 2.053119869 = 16819 * 2^-13 * 2.562915447 = 20995 * 2^-13 * 3.072711026 = 25172 * 2^-13 */ #define F_0_298 2446 #define F_0_390 3196 #define F_0_541 4433 #define F_0_765 6270 #define F_0_899 7373 #define F_1_175 9633 #define F_1_501 12299 #define F_1_847 15137 #define F_1_961 16069 #define F_2_053 16819 #define F_2_562 20995 #define F_3_072 25172 #define F_1_175_MINUS_1_961 (F_1_175 - F_1_961) #define F_1_175_MINUS_0_390 (F_1_175 - F_0_390) #define F_0_541_MINUS_1_847 (F_0_541 - F_1_847) #define F_3_072_MINUS_2_562 (F_3_072 - F_2_562) #define F_0_298_MINUS_0_899 (F_0_298 - F_0_899) #define F_1_501_MINUS_0_899 (F_1_501 - F_0_899) #define F_2_053_MINUS_2_562 (F_2_053 - F_2_562) #define F_0_541_PLUS_0_765 (F_0_541 + F_0_765) ALIGN(16) static const int16_t jsimd_idct_islow_neon_consts[] = { F_0_899, F_0_541, F_2_562, F_0_298_MINUS_0_899, F_1_501_MINUS_0_899, F_2_053_MINUS_2_562, F_0_541_PLUS_0_765, F_1_175, F_1_175_MINUS_0_390, F_0_541_MINUS_1_847, F_3_072_MINUS_2_562, F_1_175_MINUS_1_961, 0, 0, 0, 0 }; /* Forward declaration of regular and sparse IDCT helper functions */ static INLINE void jsimd_idct_islow_pass1_regular(int16x4_t row0, int16x4_t row1, int16x4_t row2, int16x4_t row3, int16x4_t row4, int16x4_t row5, int16x4_t row6, int16x4_t row7, int16x4_t quant_row0, int16x4_t quant_row1, int16x4_t quant_row2, int16x4_t quant_row3, int16x4_t quant_row4, int16x4_t quant_row5, int16x4_t quant_row6, int16x4_t quant_row7, int16_t *workspace_1, int16_t *workspace_2); static INLINE void jsimd_idct_islow_pass1_sparse(int16x4_t row0, int16x4_t row1, int16x4_t row2, int16x4_t row3, int16x4_t quant_row0, int16x4_t quant_row1, int16x4_t quant_row2, int16x4_t quant_row3, int16_t *workspace_1, int16_t *workspace_2); static INLINE void jsimd_idct_islow_pass2_regular(int16_t *workspace, JSAMPARRAY output_buf, JDIMENSION output_col, unsigned buf_offset); static INLINE void jsimd_idct_islow_pass2_sparse(int16_t *workspace, JSAMPARRAY output_buf, JDIMENSION output_col, unsigned buf_offset); /* Perform dequantization and inverse DCT on one block of coefficients. For * reference, the C implementation (jpeg_idct_slow()) can be found in * jidctint.c. * * Optimization techniques used for fast data access: * * In each pass, the inverse DCT is computed for the left and right 4x8 halves * of the DCT block. This avoids spilling due to register pressure, and the * increased granularity allows for an optimized calculation depending on the * values of the DCT coefficients. Between passes, intermediate data is stored * in 4x8 workspace buffers. * * Transposing the 8x8 DCT block after each pass can be achieved by transposing * each of the four 4x4 quadrants and swapping quadrants 1 and 2 (refer to the * diagram below.) Swapping quadrants is cheap, since the second pass can just * swap the workspace buffer pointers. * * +-------+-------+ +-------+-------+ * | | | | | | * | 0 | 1 | | 0 | 2 | * | | | transpose | | | * +-------+-------+ ------> +-------+-------+ * | | | | | | * | 2 | 3 | | 1 | 3 | * | | | | | | * +-------+-------+ +-------+-------+ * * Optimization techniques used to accelerate the inverse DCT calculation: * * In a DCT coefficient block, the coefficients are increasingly likely to be 0 * as you move diagonally from top left to bottom right. If whole rows of * coefficients are 0, then the inverse DCT calculation can be simplified. On * the first pass of the inverse DCT, we test for three special cases before * defaulting to a full "regular" inverse DCT: * * 1) Coefficients in rows 4-7 are all zero. In this case, we perform a * "sparse" simplified inverse DCT on rows 0-3. * 2) AC coefficients (rows 1-7) are all zero. In this case, the inverse DCT * result is equal to the dequantized DC coefficients. * 3) AC and DC coefficients are all zero. In this case, the inverse DCT * result is all zero. For the left 4x8 half, this is handled identically * to Case 2 above. For the right 4x8 half, we do no work and signal that * the "sparse" algorithm is required for the second pass. * * In the second pass, only a single special case is tested: whether the AC and * DC coefficients were all zero in the right 4x8 block during the first pass * (refer to Case 3 above.) If this is the case, then a "sparse" variant of * the second pass is performed for both the left and right halves of the DCT * block. (The transposition after the first pass means that the right 4x8 * block during the first pass becomes rows 4-7 during the second pass.) */ void jsimd_idct_islow_neon(void *dct_table, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col) { ISLOW_MULT_TYPE *quantptr = dct_table; int16_t workspace_l[8 * DCTSIZE / 2]; int16_t workspace_r[8 * DCTSIZE / 2]; /* Compute IDCT first pass on left 4x8 coefficient block. */ /* Load DCT coefficients in left 4x8 block. */ int16x4_t row0 = vld1_s16(coef_block + 0 * DCTSIZE); int16x4_t row1 = vld1_s16(coef_block + 1 * DCTSIZE); int16x4_t row2 = vld1_s16(coef_block + 2 * DCTSIZE); int16x4_t row3 = vld1_s16(coef_block + 3 * DCTSIZE); int16x4_t row4 = vld1_s16(coef_block + 4 * DCTSIZE); int16x4_t row5 = vld1_s16(coef_block + 5 * DCTSIZE); int16x4_t row6 = vld1_s16(coef_block + 6 * DCTSIZE); int16x4_t row7 = vld1_s16(coef_block + 7 * DCTSIZE); /* Load quantization table for left 4x8 block. */ int16x4_t quant_row0 = vld1_s16(quantptr + 0 * DCTSIZE); int16x4_t quant_row1 = vld1_s16(quantptr + 1 * DCTSIZE); int16x4_t quant_row2 = vld1_s16(quantptr + 2 * DCTSIZE); int16x4_t quant_row3 = vld1_s16(quantptr + 3 * DCTSIZE); int16x4_t quant_row4 = vld1_s16(quantptr + 4 * DCTSIZE); int16x4_t quant_row5 = vld1_s16(quantptr + 5 * DCTSIZE); int16x4_t quant_row6 = vld1_s16(quantptr + 6 * DCTSIZE); int16x4_t quant_row7 = vld1_s16(quantptr + 7 * DCTSIZE); /* Construct bitmap to test if DCT coefficients in left 4x8 block are 0. */ int16x4_t bitmap = vorr_s16(row7, row6); bitmap = vorr_s16(bitmap, row5); bitmap = vorr_s16(bitmap, row4); int64_t bitmap_rows_4567 = vget_lane_s64(vreinterpret_s64_s16(bitmap), 0); if (bitmap_rows_4567 == 0) { bitmap = vorr_s16(bitmap, row3); bitmap = vorr_s16(bitmap, row2); bitmap = vorr_s16(bitmap, row1); int64_t left_ac_bitmap = vget_lane_s64(vreinterpret_s64_s16(bitmap), 0); if (left_ac_bitmap == 0) { int16x4_t dcval = vshl_n_s16(vmul_s16(row0, quant_row0), PASS1_BITS); int16x4x4_t quadrant = { { dcval, dcval, dcval, dcval } }; /* Store 4x4 blocks to workspace, transposing in the process. */ vst4_s16(workspace_l, quadrant); vst4_s16(workspace_r, quadrant); } else { jsimd_idct_islow_pass1_sparse(row0, row1, row2, row3, quant_row0, quant_row1, quant_row2, quant_row3, workspace_l, workspace_r); } } else { jsimd_idct_islow_pass1_regular(row0, row1, row2, row3, row4, row5, row6, row7, quant_row0, quant_row1, quant_row2, quant_row3, quant_row4, quant_row5, quant_row6, quant_row7, workspace_l, workspace_r); } /* Compute IDCT first pass on right 4x8 coefficient block. */ /* Load DCT coefficients in right 4x8 block. */ row0 = vld1_s16(coef_block + 0 * DCTSIZE + 4); row1 = vld1_s16(coef_block + 1 * DCTSIZE + 4); row2 = vld1_s16(coef_block + 2 * DCTSIZE + 4); row3 = vld1_s16(coef_block + 3 * DCTSIZE + 4); row4 = vld1_s16(coef_block + 4 * DCTSIZE + 4); row5 = vld1_s16(coef_block + 5 * DCTSIZE + 4); row6 = vld1_s16(coef_block + 6 * DCTSIZE + 4); row7 = vld1_s16(coef_block + 7 * DCTSIZE + 4); /* Load quantization table for right 4x8 block. */ quant_row0 = vld1_s16(quantptr + 0 * DCTSIZE + 4); quant_row1 = vld1_s16(quantptr + 1 * DCTSIZE + 4); quant_row2 = vld1_s16(quantptr + 2 * DCTSIZE + 4); quant_row3 = vld1_s16(quantptr + 3 * DCTSIZE + 4); quant_row4 = vld1_s16(quantptr + 4 * DCTSIZE + 4); quant_row5 = vld1_s16(quantptr + 5 * DCTSIZE + 4); quant_row6 = vld1_s16(quantptr + 6 * DCTSIZE + 4); quant_row7 = vld1_s16(quantptr + 7 * DCTSIZE + 4); /* Construct bitmap to test if DCT coefficients in right 4x8 block are 0. */ bitmap = vorr_s16(row7, row6); bitmap = vorr_s16(bitmap, row5); bitmap = vorr_s16(bitmap, row4); bitmap_rows_4567 = vget_lane_s64(vreinterpret_s64_s16(bitmap), 0); bitmap = vorr_s16(bitmap, row3); bitmap = vorr_s16(bitmap, row2); bitmap = vorr_s16(bitmap, row1); int64_t right_ac_bitmap = vget_lane_s64(vreinterpret_s64_s16(bitmap), 0); /* If this remains non-zero, a "regular" second pass will be performed. */ int64_t right_ac_dc_bitmap = 1; if (right_ac_bitmap == 0) { bitmap = vorr_s16(bitmap, row0); right_ac_dc_bitmap = vget_lane_s64(vreinterpret_s64_s16(bitmap), 0); if (right_ac_dc_bitmap != 0) { int16x4_t dcval = vshl_n_s16(vmul_s16(row0, quant_row0), PASS1_BITS); int16x4x4_t quadrant = { { dcval, dcval, dcval, dcval } }; /* Store 4x4 blocks to workspace, transposing in the process. */ vst4_s16(workspace_l + 4 * DCTSIZE / 2, quadrant); vst4_s16(workspace_r + 4 * DCTSIZE / 2, quadrant); } } else { if (bitmap_rows_4567 == 0) { jsimd_idct_islow_pass1_sparse(row0, row1, row2, row3, quant_row0, quant_row1, quant_row2, quant_row3, workspace_l + 4 * DCTSIZE / 2, workspace_r + 4 * DCTSIZE / 2); } else { jsimd_idct_islow_pass1_regular(row0, row1, row2, row3, row4, row5, row6, row7, quant_row0, quant_row1, quant_row2, quant_row3, quant_row4, quant_row5, quant_row6, quant_row7, workspace_l + 4 * DCTSIZE / 2, workspace_r + 4 * DCTSIZE / 2); } } /* Second pass: compute IDCT on rows in workspace. */ /* If all coefficients in right 4x8 block are 0, use "sparse" second pass. */ if (right_ac_dc_bitmap == 0) { jsimd_idct_islow_pass2_sparse(workspace_l, output_buf, output_col, 0); jsimd_idct_islow_pass2_sparse(workspace_r, output_buf, output_col, 4); } else { jsimd_idct_islow_pass2_regular(workspace_l, output_buf, output_col, 0); jsimd_idct_islow_pass2_regular(workspace_r, output_buf, output_col, 4); } } /* Perform dequantization and the first pass of the accurate inverse DCT on a * 4x8 block of coefficients. (To process the full 8x8 DCT block, this * function-- or some other optimized variant-- needs to be called for both the * left and right 4x8 blocks.) * * This "regular" version assumes that no optimization can be made to the IDCT * calculation, since no useful set of AC coefficients is all 0. * * The original C implementation of the accurate IDCT (jpeg_idct_slow()) can be * found in jidctint.c. Algorithmic changes made here are documented inline. */ static INLINE void jsimd_idct_islow_pass1_regular(int16x4_t row0, int16x4_t row1, int16x4_t row2, int16x4_t row3, int16x4_t row4, int16x4_t row5, int16x4_t row6, int16x4_t row7, int16x4_t quant_row0, int16x4_t quant_row1, int16x4_t quant_row2, int16x4_t quant_row3, int16x4_t quant_row4, int16x4_t quant_row5, int16x4_t quant_row6, int16x4_t quant_row7, int16_t *workspace_1, int16_t *workspace_2) { /* Load constants for IDCT computation. */ #ifdef HAVE_VLD1_S16_X3 const int16x4x3_t consts = vld1_s16_x3(jsimd_idct_islow_neon_consts); #else const int16x4_t consts1 = vld1_s16(jsimd_idct_islow_neon_consts); const int16x4_t consts2 = vld1_s16(jsimd_idct_islow_neon_consts + 4); const int16x4_t consts3 = vld1_s16(jsimd_idct_islow_neon_consts + 8); const int16x4x3_t consts = { { consts1, consts2, consts3 } }; #endif /* Even part */ int16x4_t z2_s16 = vmul_s16(row2, quant_row2); int16x4_t z3_s16 = vmul_s16(row6, quant_row6); int32x4_t tmp2 = vmull_lane_s16(z2_s16, consts.val[0], 1); int32x4_t tmp3 = vmull_lane_s16(z2_s16, consts.val[1], 2); tmp2 = vmlal_lane_s16(tmp2, z3_s16, consts.val[2], 1); tmp3 = vmlal_lane_s16(tmp3, z3_s16, consts.val[0], 1); z2_s16 = vmul_s16(row0, quant_row0); z3_s16 = vmul_s16(row4, quant_row4); int32x4_t tmp0 = vshll_n_s16(vadd_s16(z2_s16, z3_s16), CONST_BITS); int32x4_t tmp1 = vshll_n_s16(vsub_s16(z2_s16, z3_s16), CONST_BITS); int32x4_t tmp10 = vaddq_s32(tmp0, tmp3); int32x4_t tmp13 = vsubq_s32(tmp0, tmp3); int32x4_t tmp11 = vaddq_s32(tmp1, tmp2); int32x4_t tmp12 = vsubq_s32(tmp1, tmp2); /* Odd part */ int16x4_t tmp0_s16 = vmul_s16(row7, quant_row7); int16x4_t tmp1_s16 = vmul_s16(row5, quant_row5); int16x4_t tmp2_s16 = vmul_s16(row3, quant_row3); int16x4_t tmp3_s16 = vmul_s16(row1, quant_row1); z3_s16 = vadd_s16(tmp0_s16, tmp2_s16); int16x4_t z4_s16 = vadd_s16(tmp1_s16, tmp3_s16); /* Implementation as per jpeg_idct_islow() in jidctint.c: * z5 = (z3 + z4) * 1.175875602; * z3 = z3 * -1.961570560; z4 = z4 * -0.390180644; * z3 += z5; z4 += z5; * * This implementation: * z3 = z3 * (1.175875602 - 1.961570560) + z4 * 1.175875602; * z4 = z3 * 1.175875602 + z4 * (1.175875602 - 0.390180644); */ int32x4_t z3 = vmull_lane_s16(z3_s16, consts.val[2], 3); int32x4_t z4 = vmull_lane_s16(z3_s16, consts.val[1], 3); z3 = vmlal_lane_s16(z3, z4_s16, consts.val[1], 3); z4 = vmlal_lane_s16(z4, z4_s16, consts.val[2], 0); /* Implementation as per jpeg_idct_islow() in jidctint.c: * z1 = tmp0 + tmp3; z2 = tmp1 + tmp2; * tmp0 = tmp0 * 0.298631336; tmp1 = tmp1 * 2.053119869; * tmp2 = tmp2 * 3.072711026; tmp3 = tmp3 * 1.501321110; * z1 = z1 * -0.899976223; z2 = z2 * -2.562915447; * tmp0 += z1 + z3; tmp1 += z2 + z4; * tmp2 += z2 + z3; tmp3 += z1 + z4; * * This implementation: * tmp0 = tmp0 * (0.298631336 - 0.899976223) + tmp3 * -0.899976223; * tmp1 = tmp1 * (2.053119869 - 2.562915447) + tmp2 * -2.562915447; * tmp2 = tmp1 * -2.562915447 + tmp2 * (3.072711026 - 2.562915447); * tmp3 = tmp0 * -0.899976223 + tmp3 * (1.501321110 - 0.899976223); * tmp0 += z3; tmp1 += z4; * tmp2 += z3; tmp3 += z4; */ tmp0 = vmull_lane_s16(tmp0_s16, consts.val[0], 3); tmp1 = vmull_lane_s16(tmp1_s16, consts.val[1], 1); tmp2 = vmull_lane_s16(tmp2_s16, consts.val[2], 2); tmp3 = vmull_lane_s16(tmp3_s16, consts.val[1], 0); tmp0 = vmlsl_lane_s16(tmp0, tmp3_s16, consts.val[0], 0); tmp1 = vmlsl_lane_s16(tmp1, tmp2_s16, consts.val[0], 2); tmp2 = vmlsl_lane_s16(tmp2, tmp1_s16, consts.val[0], 2); tmp3 = vmlsl_lane_s16(tmp3, tmp0_s16, consts.val[0], 0); tmp0 = vaddq_s32(tmp0, z3); tmp1 = vaddq_s32(tmp1, z4); tmp2 = vaddq_s32(tmp2, z3); tmp3 = vaddq_s32(tmp3, z4); /* Final output stage: descale and narrow to 16-bit. */ int16x4x4_t rows_0123 = { { vrshrn_n_s32(vaddq_s32(tmp10, tmp3), DESCALE_P1), vrshrn_n_s32(vaddq_s32(tmp11, tmp2), DESCALE_P1), vrshrn_n_s32(vaddq_s32(tmp12, tmp1), DESCALE_P1), vrshrn_n_s32(vaddq_s32(tmp13, tmp0), DESCALE_P1) } }; int16x4x4_t rows_4567 = { { vrshrn_n_s32(vsubq_s32(tmp13, tmp0), DESCALE_P1), vrshrn_n_s32(vsubq_s32(tmp12, tmp1), DESCALE_P1), vrshrn_n_s32(vsubq_s32(tmp11, tmp2), DESCALE_P1), vrshrn_n_s32(vsubq_s32(tmp10, tmp3), DESCALE_P1) } }; /* Store 4x4 blocks to the intermediate workspace, ready for the second pass. * (VST4 transposes the blocks. We need to operate on rows in the next * pass.) */ vst4_s16(workspace_1, rows_0123); vst4_s16(workspace_2, rows_4567); } /* Perform dequantization and the first pass of the accurate inverse DCT on a * 4x8 block of coefficients. * * This "sparse" version assumes that the AC coefficients in rows 4-7 are all * 0. This simplifies the IDCT calculation, accelerating overall performance. */ static INLINE void jsimd_idct_islow_pass1_sparse(int16x4_t row0, int16x4_t row1, int16x4_t row2, int16x4_t row3, int16x4_t quant_row0, int16x4_t quant_row1, int16x4_t quant_row2, int16x4_t quant_row3, int16_t *workspace_1, int16_t *workspace_2) { /* Load constants for IDCT computation. */ #ifdef HAVE_VLD1_S16_X3 const int16x4x3_t consts = vld1_s16_x3(jsimd_idct_islow_neon_consts); #else const int16x4_t consts1 = vld1_s16(jsimd_idct_islow_neon_consts); const int16x4_t consts2 = vld1_s16(jsimd_idct_islow_neon_consts + 4); const int16x4_t consts3 = vld1_s16(jsimd_idct_islow_neon_consts + 8); const int16x4x3_t consts = { { consts1, consts2, consts3 } }; #endif /* Even part (z3 is all 0) */ int16x4_t z2_s16 = vmul_s16(row2, quant_row2); int32x4_t tmp2 = vmull_lane_s16(z2_s16, consts.val[0], 1); int32x4_t tmp3 = vmull_lane_s16(z2_s16, consts.val[1], 2); z2_s16 = vmul_s16(row0, quant_row0); int32x4_t tmp0 = vshll_n_s16(z2_s16, CONST_BITS); int32x4_t tmp1 = vshll_n_s16(z2_s16, CONST_BITS); int32x4_t tmp10 = vaddq_s32(tmp0, tmp3); int32x4_t tmp13 = vsubq_s32(tmp0, tmp3); int32x4_t tmp11 = vaddq_s32(tmp1, tmp2); int32x4_t tmp12 = vsubq_s32(tmp1, tmp2); /* Odd part (tmp0 and tmp1 are both all 0) */ int16x4_t tmp2_s16 = vmul_s16(row3, quant_row3); int16x4_t tmp3_s16 = vmul_s16(row1, quant_row1); int16x4_t z3_s16 = tmp2_s16; int16x4_t z4_s16 = tmp3_s16; int32x4_t z3 = vmull_lane_s16(z3_s16, consts.val[2], 3); int32x4_t z4 = vmull_lane_s16(z3_s16, consts.val[1], 3); z3 = vmlal_lane_s16(z3, z4_s16, consts.val[1], 3); z4 = vmlal_lane_s16(z4, z4_s16, consts.val[2], 0); tmp0 = vmlsl_lane_s16(z3, tmp3_s16, consts.val[0], 0); tmp1 = vmlsl_lane_s16(z4, tmp2_s16, consts.val[0], 2); tmp2 = vmlal_lane_s16(z3, tmp2_s16, consts.val[2], 2); tmp3 = vmlal_lane_s16(z4, tmp3_s16, consts.val[1], 0); /* Final output stage: descale and narrow to 16-bit. */ int16x4x4_t rows_0123 = { { vrshrn_n_s32(vaddq_s32(tmp10, tmp3), DESCALE_P1), vrshrn_n_s32(vaddq_s32(tmp11, tmp2), DESCALE_P1), vrshrn_n_s32(vaddq_s32(tmp12, tmp1), DESCALE_P1), vrshrn_n_s32(vaddq_s32(tmp13, tmp0), DESCALE_P1) } }; int16x4x4_t rows_4567 = { { vrshrn_n_s32(vsubq_s32(tmp13, tmp0), DESCALE_P1), vrshrn_n_s32(vsubq_s32(tmp12, tmp1), DESCALE_P1), vrshrn_n_s32(vsubq_s32(tmp11, tmp2), DESCALE_P1), vrshrn_n_s32(vsubq_s32(tmp10, tmp3), DESCALE_P1) } }; /* Store 4x4 blocks to the intermediate workspace, ready for the second pass. * (VST4 transposes the blocks. We need to operate on rows in the next * pass.) */ vst4_s16(workspace_1, rows_0123); vst4_s16(workspace_2, rows_4567); } /* Perform the second pass of the accurate inverse DCT on a 4x8 block of * coefficients. (To process the full 8x8 DCT block, this function-- or some * other optimized variant-- needs to be called for both the right and left 4x8 * blocks.) * * This "regular" version assumes that no optimization can be made to the IDCT * calculation, since no useful set of coefficient values are all 0 after the * first pass. * * Again, the original C implementation of the accurate IDCT (jpeg_idct_slow()) * can be found in jidctint.c. Algorithmic changes made here are documented * inline. */ static INLINE void jsimd_idct_islow_pass2_regular(int16_t *workspace, JSAMPARRAY output_buf, JDIMENSION output_col, unsigned buf_offset) { /* Load constants for IDCT computation. */ #ifdef HAVE_VLD1_S16_X3 const int16x4x3_t consts = vld1_s16_x3(jsimd_idct_islow_neon_consts); #else const int16x4_t consts1 = vld1_s16(jsimd_idct_islow_neon_consts); const int16x4_t consts2 = vld1_s16(jsimd_idct_islow_neon_consts + 4); const int16x4_t consts3 = vld1_s16(jsimd_idct_islow_neon_consts + 8); const int16x4x3_t consts = { { consts1, consts2, consts3 } }; #endif /* Even part */ int16x4_t z2_s16 = vld1_s16(workspace + 2 * DCTSIZE / 2); int16x4_t z3_s16 = vld1_s16(workspace + 6 * DCTSIZE / 2); int32x4_t tmp2 = vmull_lane_s16(z2_s16, consts.val[0], 1); int32x4_t tmp3 = vmull_lane_s16(z2_s16, consts.val[1], 2); tmp2 = vmlal_lane_s16(tmp2, z3_s16, consts.val[2], 1); tmp3 = vmlal_lane_s16(tmp3, z3_s16, consts.val[0], 1); z2_s16 = vld1_s16(workspace + 0 * DCTSIZE / 2); z3_s16 = vld1_s16(workspace + 4 * DCTSIZE / 2); int32x4_t tmp0 = vshll_n_s16(vadd_s16(z2_s16, z3_s16), CONST_BITS); int32x4_t tmp1 = vshll_n_s16(vsub_s16(z2_s16, z3_s16), CONST_BITS); int32x4_t tmp10 = vaddq_s32(tmp0, tmp3); int32x4_t tmp13 = vsubq_s32(tmp0, tmp3); int32x4_t tmp11 = vaddq_s32(tmp1, tmp2); int32x4_t tmp12 = vsubq_s32(tmp1, tmp2); /* Odd part */ int16x4_t tmp0_s16 = vld1_s16(workspace + 7 * DCTSIZE / 2); int16x4_t tmp1_s16 = vld1_s16(workspace + 5 * DCTSIZE / 2); int16x4_t tmp2_s16 = vld1_s16(workspace + 3 * DCTSIZE / 2); int16x4_t tmp3_s16 = vld1_s16(workspace + 1 * DCTSIZE / 2); z3_s16 = vadd_s16(tmp0_s16, tmp2_s16); int16x4_t z4_s16 = vadd_s16(tmp1_s16, tmp3_s16); /* Implementation as per jpeg_idct_islow() in jidctint.c: * z5 = (z3 + z4) * 1.175875602; * z3 = z3 * -1.961570560; z4 = z4 * -0.390180644; * z3 += z5; z4 += z5; * * This implementation: * z3 = z3 * (1.175875602 - 1.961570560) + z4 * 1.175875602; * z4 = z3 * 1.175875602 + z4 * (1.175875602 - 0.390180644); */ int32x4_t z3 = vmull_lane_s16(z3_s16, consts.val[2], 3); int32x4_t z4 = vmull_lane_s16(z3_s16, consts.val[1], 3); z3 = vmlal_lane_s16(z3, z4_s16, consts.val[1], 3); z4 = vmlal_lane_s16(z4, z4_s16, consts.val[2], 0); /* Implementation as per jpeg_idct_islow() in jidctint.c: * z1 = tmp0 + tmp3; z2 = tmp1 + tmp2; * tmp0 = tmp0 * 0.298631336; tmp1 = tmp1 * 2.053119869; * tmp2 = tmp2 * 3.072711026; tmp3 = tmp3 * 1.501321110; * z1 = z1 * -0.899976223; z2 = z2 * -2.562915447; * tmp0 += z1 + z3; tmp1 += z2 + z4; * tmp2 += z2 + z3; tmp3 += z1 + z4; * * This implementation: * tmp0 = tmp0 * (0.298631336 - 0.899976223) + tmp3 * -0.899976223; * tmp1 = tmp1 * (2.053119869 - 2.562915447) + tmp2 * -2.562915447; * tmp2 = tmp1 * -2.562915447 + tmp2 * (3.072711026 - 2.562915447); * tmp3 = tmp0 * -0.899976223 + tmp3 * (1.501321110 - 0.899976223); * tmp0 += z3; tmp1 += z4; * tmp2 += z3; tmp3 += z4; */ tmp0 = vmull_lane_s16(tmp0_s16, consts.val[0], 3); tmp1 = vmull_lane_s16(tmp1_s16, consts.val[1], 1); tmp2 = vmull_lane_s16(tmp2_s16, consts.val[2], 2); tmp3 = vmull_lane_s16(tmp3_s16, consts.val[1], 0); tmp0 = vmlsl_lane_s16(tmp0, tmp3_s16, consts.val[0], 0); tmp1 = vmlsl_lane_s16(tmp1, tmp2_s16, consts.val[0], 2); tmp2 = vmlsl_lane_s16(tmp2, tmp1_s16, consts.val[0], 2); tmp3 = vmlsl_lane_s16(tmp3, tmp0_s16, consts.val[0], 0); tmp0 = vaddq_s32(tmp0, z3); tmp1 = vaddq_s32(tmp1, z4); tmp2 = vaddq_s32(tmp2, z3); tmp3 = vaddq_s32(tmp3, z4); /* Final output stage: descale and narrow to 16-bit. */ int16x8_t cols_02_s16 = vcombine_s16(vaddhn_s32(tmp10, tmp3), vaddhn_s32(tmp12, tmp1)); int16x8_t cols_13_s16 = vcombine_s16(vaddhn_s32(tmp11, tmp2), vaddhn_s32(tmp13, tmp0)); int16x8_t cols_46_s16 = vcombine_s16(vsubhn_s32(tmp13, tmp0), vsubhn_s32(tmp11, tmp2)); int16x8_t cols_57_s16 = vcombine_s16(vsubhn_s32(tmp12, tmp1), vsubhn_s32(tmp10, tmp3)); /* Descale and narrow to 8-bit. */ int8x8_t cols_02_s8 = vqrshrn_n_s16(cols_02_s16, DESCALE_P2 - 16); int8x8_t cols_13_s8 = vqrshrn_n_s16(cols_13_s16, DESCALE_P2 - 16); int8x8_t cols_46_s8 = vqrshrn_n_s16(cols_46_s16, DESCALE_P2 - 16); int8x8_t cols_57_s8 = vqrshrn_n_s16(cols_57_s16, DESCALE_P2 - 16); /* Clamp to range [0-255]. */ uint8x8_t cols_02_u8 = vadd_u8(vreinterpret_u8_s8(cols_02_s8), vdup_n_u8(CENTERJSAMPLE)); uint8x8_t cols_13_u8 = vadd_u8(vreinterpret_u8_s8(cols_13_s8), vdup_n_u8(CENTERJSAMPLE)); uint8x8_t cols_46_u8 = vadd_u8(vreinterpret_u8_s8(cols_46_s8), vdup_n_u8(CENTERJSAMPLE)); uint8x8_t cols_57_u8 = vadd_u8(vreinterpret_u8_s8(cols_57_s8), vdup_n_u8(CENTERJSAMPLE)); /* Transpose 4x8 block and store to memory. (Zipping adjacent columns * together allows us to store 16-bit elements.) */ uint8x8x2_t cols_01_23 = vzip_u8(cols_02_u8, cols_13_u8); uint8x8x2_t cols_45_67 = vzip_u8(cols_46_u8, cols_57_u8); uint16x4x4_t cols_01_23_45_67 = { { vreinterpret_u16_u8(cols_01_23.val[0]), vreinterpret_u16_u8(cols_01_23.val[1]), vreinterpret_u16_u8(cols_45_67.val[0]), vreinterpret_u16_u8(cols_45_67.val[1]) } }; JSAMPROW outptr0 = output_buf[buf_offset + 0] + output_col; JSAMPROW outptr1 = output_buf[buf_offset + 1] + output_col; JSAMPROW outptr2 = output_buf[buf_offset + 2] + output_col; JSAMPROW outptr3 = output_buf[buf_offset + 3] + output_col; /* VST4 of 16-bit elements completes the transpose. */ vst4_lane_u16((uint16_t *)outptr0, cols_01_23_45_67, 0); vst4_lane_u16((uint16_t *)outptr1, cols_01_23_45_67, 1); vst4_lane_u16((uint16_t *)outptr2, cols_01_23_45_67, 2); vst4_lane_u16((uint16_t *)outptr3, cols_01_23_45_67, 3); } /* Performs the second pass of the accurate inverse DCT on a 4x8 block * of coefficients. * * This "sparse" version assumes that the coefficient values (after the first * pass) in rows 4-7 are all 0. This simplifies the IDCT calculation, * accelerating overall performance. */ static INLINE void jsimd_idct_islow_pass2_sparse(int16_t *workspace, JSAMPARRAY output_buf, JDIMENSION output_col, unsigned buf_offset) { /* Load constants for IDCT computation. */ #ifdef HAVE_VLD1_S16_X3 const int16x4x3_t consts = vld1_s16_x3(jsimd_idct_islow_neon_consts); #else const int16x4_t consts1 = vld1_s16(jsimd_idct_islow_neon_consts); const int16x4_t consts2 = vld1_s16(jsimd_idct_islow_neon_consts + 4); const int16x4_t consts3 = vld1_s16(jsimd_idct_islow_neon_consts + 8); const int16x4x3_t consts = { { consts1, consts2, consts3 } }; #endif /* Even part (z3 is all 0) */ int16x4_t z2_s16 = vld1_s16(workspace + 2 * DCTSIZE / 2); int32x4_t tmp2 = vmull_lane_s16(z2_s16, consts.val[0], 1); int32x4_t tmp3 = vmull_lane_s16(z2_s16, consts.val[1], 2); z2_s16 = vld1_s16(workspace + 0 * DCTSIZE / 2); int32x4_t tmp0 = vshll_n_s16(z2_s16, CONST_BITS); int32x4_t tmp1 = vshll_n_s16(z2_s16, CONST_BITS); int32x4_t tmp10 = vaddq_s32(tmp0, tmp3); int32x4_t tmp13 = vsubq_s32(tmp0, tmp3); int32x4_t tmp11 = vaddq_s32(tmp1, tmp2); int32x4_t tmp12 = vsubq_s32(tmp1, tmp2); /* Odd part (tmp0 and tmp1 are both all 0) */ int16x4_t tmp2_s16 = vld1_s16(workspace + 3 * DCTSIZE / 2); int16x4_t tmp3_s16 = vld1_s16(workspace + 1 * DCTSIZE / 2); int16x4_t z3_s16 = tmp2_s16; int16x4_t z4_s16 = tmp3_s16; int32x4_t z3 = vmull_lane_s16(z3_s16, consts.val[2], 3); z3 = vmlal_lane_s16(z3, z4_s16, consts.val[1], 3); int32x4_t z4 = vmull_lane_s16(z3_s16, consts.val[1], 3); z4 = vmlal_lane_s16(z4, z4_s16, consts.val[2], 0); tmp0 = vmlsl_lane_s16(z3, tmp3_s16, consts.val[0], 0); tmp1 = vmlsl_lane_s16(z4, tmp2_s16, consts.val[0], 2); tmp2 = vmlal_lane_s16(z3, tmp2_s16, consts.val[2], 2); tmp3 = vmlal_lane_s16(z4, tmp3_s16, consts.val[1], 0); /* Final output stage: descale and narrow to 16-bit. */ int16x8_t cols_02_s16 = vcombine_s16(vaddhn_s32(tmp10, tmp3), vaddhn_s32(tmp12, tmp1)); int16x8_t cols_13_s16 = vcombine_s16(vaddhn_s32(tmp11, tmp2), vaddhn_s32(tmp13, tmp0)); int16x8_t cols_46_s16 = vcombine_s16(vsubhn_s32(tmp13, tmp0), vsubhn_s32(tmp11, tmp2)); int16x8_t cols_57_s16 = vcombine_s16(vsubhn_s32(tmp12, tmp1), vsubhn_s32(tmp10, tmp3)); /* Descale and narrow to 8-bit. */ int8x8_t cols_02_s8 = vqrshrn_n_s16(cols_02_s16, DESCALE_P2 - 16); int8x8_t cols_13_s8 = vqrshrn_n_s16(cols_13_s16, DESCALE_P2 - 16); int8x8_t cols_46_s8 = vqrshrn_n_s16(cols_46_s16, DESCALE_P2 - 16); int8x8_t cols_57_s8 = vqrshrn_n_s16(cols_57_s16, DESCALE_P2 - 16); /* Clamp to range [0-255]. */ uint8x8_t cols_02_u8 = vadd_u8(vreinterpret_u8_s8(cols_02_s8), vdup_n_u8(CENTERJSAMPLE)); uint8x8_t cols_13_u8 = vadd_u8(vreinterpret_u8_s8(cols_13_s8), vdup_n_u8(CENTERJSAMPLE)); uint8x8_t cols_46_u8 = vadd_u8(vreinterpret_u8_s8(cols_46_s8), vdup_n_u8(CENTERJSAMPLE)); uint8x8_t cols_57_u8 = vadd_u8(vreinterpret_u8_s8(cols_57_s8), vdup_n_u8(CENTERJSAMPLE)); /* Transpose 4x8 block and store to memory. (Zipping adjacent columns * together allows us to store 16-bit elements.) */ uint8x8x2_t cols_01_23 = vzip_u8(cols_02_u8, cols_13_u8); uint8x8x2_t cols_45_67 = vzip_u8(cols_46_u8, cols_57_u8); uint16x4x4_t cols_01_23_45_67 = { { vreinterpret_u16_u8(cols_01_23.val[0]), vreinterpret_u16_u8(cols_01_23.val[1]), vreinterpret_u16_u8(cols_45_67.val[0]), vreinterpret_u16_u8(cols_45_67.val[1]) } }; JSAMPROW outptr0 = output_buf[buf_offset + 0] + output_col; JSAMPROW outptr1 = output_buf[buf_offset + 1] + output_col; JSAMPROW outptr2 = output_buf[buf_offset + 2] + output_col; JSAMPROW outptr3 = output_buf[buf_offset + 3] + output_col; /* VST4 of 16-bit elements completes the transpose. */ vst4_lane_u16((uint16_t *)outptr0, cols_01_23_45_67, 0); vst4_lane_u16((uint16_t *)outptr1, cols_01_23_45_67, 1); vst4_lane_u16((uint16_t *)outptr2, cols_01_23_45_67, 2); vst4_lane_u16((uint16_t *)outptr3, cols_01_23_45_67, 3); }