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mozjpeg/simd/arm/aarch64/jchuff-neon.c
DRC 98bc3eeb3a Neon/AArch64: Fix/suppress UBSan warnings 
- Suppress a UBSan warning regarding storing a 64-bit value to a
  non-64-bit-aligned address.  That behavior is technically undefined
  per the C spec but is supported in the context of the AArch64
  architecture and compilers.

- Explicitly promote block_diff[i] to unsigned int prior to left
  shifting it, in order to avoid a UBSan warning.  This warning also
  described behavior that is technically undefined per the C spec but is
  supported in the context of the AArch64 architecture and compilers.
  Changing the type cast order eliminated the warning without changing
  the generated assembly code.

Closes #582
2022-02-25 00:02:14 -06:00

412 lines
18 KiB
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/*
* jchuff-neon.c - Huffman entropy encoding (64-bit Arm Neon)
*
* Copyright (C) 2020-2021, Arm Limited. All Rights Reserved.
* Copyright (C) 2020, 2022, 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.
*
* NOTE: All referenced figures are from
* Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994.
*/
#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 "../jchuff.h"
#include "neon-compat.h"
#include <limits.h>
#include <arm_neon.h>
ALIGN(16) static const uint8_t jsimd_huff_encode_one_block_consts[] = {
0, 1, 2, 3, 16, 17, 32, 33,
18, 19, 4, 5, 6, 7, 20, 21,
34, 35, 48, 49, 255, 255, 50, 51,
36, 37, 22, 23, 8, 9, 10, 11,
255, 255, 6, 7, 20, 21, 34, 35,
48, 49, 255, 255, 50, 51, 36, 37,
54, 55, 40, 41, 26, 27, 12, 13,
14, 15, 28, 29, 42, 43, 56, 57,
6, 7, 20, 21, 34, 35, 48, 49,
50, 51, 36, 37, 22, 23, 8, 9,
26, 27, 12, 13, 255, 255, 14, 15,
28, 29, 42, 43, 56, 57, 255, 255,
52, 53, 54, 55, 40, 41, 26, 27,
12, 13, 255, 255, 14, 15, 28, 29,
26, 27, 40, 41, 42, 43, 28, 29,
14, 15, 30, 31, 44, 45, 46, 47
};
/* The AArch64 implementation of the FLUSH() macro triggers a UBSan misaligned
* address warning because the macro sometimes writes a 64-bit value to a
* non-64-bit-aligned address. That behavior is technically undefined per
* the C specification, but it is supported by the AArch64 architecture and
* compilers.
*/
#if defined(__has_feature)
#if __has_feature(undefined_behavior_sanitizer)
__attribute__((no_sanitize("alignment")))
#endif
#endif
JOCTET *jsimd_huff_encode_one_block_neon(void *state, JOCTET *buffer,
JCOEFPTR block, int last_dc_val,
c_derived_tbl *dctbl,
c_derived_tbl *actbl)
{
uint16_t block_diff[DCTSIZE2];
/* Load lookup table indices for rows of zig-zag ordering. */
#ifdef HAVE_VLD1Q_U8_X4
const uint8x16x4_t idx_rows_0123 =
vld1q_u8_x4(jsimd_huff_encode_one_block_consts + 0 * DCTSIZE);
const uint8x16x4_t idx_rows_4567 =
vld1q_u8_x4(jsimd_huff_encode_one_block_consts + 8 * DCTSIZE);
#else
/* GCC does not currently support intrinsics vl1dq_<type>_x4(). */
const uint8x16x4_t idx_rows_0123 = { {
vld1q_u8(jsimd_huff_encode_one_block_consts + 0 * DCTSIZE),
vld1q_u8(jsimd_huff_encode_one_block_consts + 2 * DCTSIZE),
vld1q_u8(jsimd_huff_encode_one_block_consts + 4 * DCTSIZE),
vld1q_u8(jsimd_huff_encode_one_block_consts + 6 * DCTSIZE)
} };
const uint8x16x4_t idx_rows_4567 = { {
vld1q_u8(jsimd_huff_encode_one_block_consts + 8 * DCTSIZE),
vld1q_u8(jsimd_huff_encode_one_block_consts + 10 * DCTSIZE),
vld1q_u8(jsimd_huff_encode_one_block_consts + 12 * DCTSIZE),
vld1q_u8(jsimd_huff_encode_one_block_consts + 14 * DCTSIZE)
} };
#endif
/* Load 8x8 block of DCT coefficients. */
#ifdef HAVE_VLD1Q_U8_X4
const int8x16x4_t tbl_rows_0123 =
vld1q_s8_x4((int8_t *)(block + 0 * DCTSIZE));
const int8x16x4_t tbl_rows_4567 =
vld1q_s8_x4((int8_t *)(block + 4 * DCTSIZE));
#else
const int8x16x4_t tbl_rows_0123 = { {
vld1q_s8((int8_t *)(block + 0 * DCTSIZE)),
vld1q_s8((int8_t *)(block + 1 * DCTSIZE)),
vld1q_s8((int8_t *)(block + 2 * DCTSIZE)),
vld1q_s8((int8_t *)(block + 3 * DCTSIZE))
} };
const int8x16x4_t tbl_rows_4567 = { {
vld1q_s8((int8_t *)(block + 4 * DCTSIZE)),
vld1q_s8((int8_t *)(block + 5 * DCTSIZE)),
vld1q_s8((int8_t *)(block + 6 * DCTSIZE)),
vld1q_s8((int8_t *)(block + 7 * DCTSIZE))
} };
#endif
/* Initialise extra lookup tables. */
const int8x16x4_t tbl_rows_2345 = { {
tbl_rows_0123.val[2], tbl_rows_0123.val[3],
tbl_rows_4567.val[0], tbl_rows_4567.val[1]
} };
const int8x16x3_t tbl_rows_567 =
{ { tbl_rows_4567.val[1], tbl_rows_4567.val[2], tbl_rows_4567.val[3] } };
/* Shuffle coefficients into zig-zag order. */
int16x8_t row0 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_0123, idx_rows_0123.val[0]));
int16x8_t row1 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_0123, idx_rows_0123.val[1]));
int16x8_t row2 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_2345, idx_rows_0123.val[2]));
int16x8_t row3 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_0123, idx_rows_0123.val[3]));
int16x8_t row4 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_4567, idx_rows_4567.val[0]));
int16x8_t row5 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_2345, idx_rows_4567.val[1]));
int16x8_t row6 =
vreinterpretq_s16_s8(vqtbl4q_s8(tbl_rows_4567, idx_rows_4567.val[2]));
int16x8_t row7 =
vreinterpretq_s16_s8(vqtbl3q_s8(tbl_rows_567, idx_rows_4567.val[3]));
/* Compute DC coefficient difference value (F.1.1.5.1). */
row0 = vsetq_lane_s16(block[0] - last_dc_val, row0, 0);
/* Initialize AC coefficient lanes not reachable by lookup tables. */
row1 =
vsetq_lane_s16(vgetq_lane_s16(vreinterpretq_s16_s8(tbl_rows_4567.val[0]),
0), row1, 2);
row2 =
vsetq_lane_s16(vgetq_lane_s16(vreinterpretq_s16_s8(tbl_rows_0123.val[1]),
4), row2, 0);
row2 =
vsetq_lane_s16(vgetq_lane_s16(vreinterpretq_s16_s8(tbl_rows_4567.val[2]),
0), row2, 5);
row5 =
vsetq_lane_s16(vgetq_lane_s16(vreinterpretq_s16_s8(tbl_rows_0123.val[1]),
7), row5, 2);
row5 =
vsetq_lane_s16(vgetq_lane_s16(vreinterpretq_s16_s8(tbl_rows_4567.val[2]),
3), row5, 7);
row6 =
vsetq_lane_s16(vgetq_lane_s16(vreinterpretq_s16_s8(tbl_rows_0123.val[3]),
7), row6, 5);
/* DCT block is now in zig-zag order; start Huffman encoding process. */
/* Construct bitmap to accelerate encoding of AC coefficients. A set bit
* means that the corresponding coefficient != 0.
*/
uint16x8_t row0_ne_0 = vtstq_s16(row0, row0);
uint16x8_t row1_ne_0 = vtstq_s16(row1, row1);
uint16x8_t row2_ne_0 = vtstq_s16(row2, row2);
uint16x8_t row3_ne_0 = vtstq_s16(row3, row3);
uint16x8_t row4_ne_0 = vtstq_s16(row4, row4);
uint16x8_t row5_ne_0 = vtstq_s16(row5, row5);
uint16x8_t row6_ne_0 = vtstq_s16(row6, row6);
uint16x8_t row7_ne_0 = vtstq_s16(row7, row7);
uint8x16_t row10_ne_0 = vuzp1q_u8(vreinterpretq_u8_u16(row1_ne_0),
vreinterpretq_u8_u16(row0_ne_0));
uint8x16_t row32_ne_0 = vuzp1q_u8(vreinterpretq_u8_u16(row3_ne_0),
vreinterpretq_u8_u16(row2_ne_0));
uint8x16_t row54_ne_0 = vuzp1q_u8(vreinterpretq_u8_u16(row5_ne_0),
vreinterpretq_u8_u16(row4_ne_0));
uint8x16_t row76_ne_0 = vuzp1q_u8(vreinterpretq_u8_u16(row7_ne_0),
vreinterpretq_u8_u16(row6_ne_0));
/* { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 } */
const uint8x16_t bitmap_mask =
vreinterpretq_u8_u64(vdupq_n_u64(0x0102040810204080));
uint8x16_t bitmap_rows_10 = vandq_u8(row10_ne_0, bitmap_mask);
uint8x16_t bitmap_rows_32 = vandq_u8(row32_ne_0, bitmap_mask);
uint8x16_t bitmap_rows_54 = vandq_u8(row54_ne_0, bitmap_mask);
uint8x16_t bitmap_rows_76 = vandq_u8(row76_ne_0, bitmap_mask);
uint8x16_t bitmap_rows_3210 = vpaddq_u8(bitmap_rows_32, bitmap_rows_10);
uint8x16_t bitmap_rows_7654 = vpaddq_u8(bitmap_rows_76, bitmap_rows_54);
uint8x16_t bitmap_rows_76543210 = vpaddq_u8(bitmap_rows_7654,
bitmap_rows_3210);
uint8x8_t bitmap_all = vpadd_u8(vget_low_u8(bitmap_rows_76543210),
vget_high_u8(bitmap_rows_76543210));
/* Shift left to remove DC bit. */
bitmap_all =
vreinterpret_u8_u64(vshl_n_u64(vreinterpret_u64_u8(bitmap_all), 1));
/* Count bits set (number of non-zero coefficients) in bitmap. */
unsigned int non_zero_coefficients = vaddv_u8(vcnt_u8(bitmap_all));
/* Move bitmap to 64-bit scalar register. */
uint64_t bitmap = vget_lane_u64(vreinterpret_u64_u8(bitmap_all), 0);
/* Set up state and bit buffer for output bitstream. */
working_state *state_ptr = (working_state *)state;
int free_bits = state_ptr->cur.free_bits;
size_t put_buffer = state_ptr->cur.put_buffer;
/* Encode DC coefficient. */
/* For negative coeffs: diff = abs(coeff) -1 = ~abs(coeff) */
int16x8_t abs_row0 = vabsq_s16(row0);
int16x8_t row0_lz = vclzq_s16(abs_row0);
uint16x8_t row0_mask = vshlq_u16(vcltzq_s16(row0), vnegq_s16(row0_lz));
uint16x8_t row0_diff = veorq_u16(vreinterpretq_u16_s16(abs_row0), row0_mask);
/* Find nbits required to specify sign and amplitude of coefficient. */
unsigned int lz = vgetq_lane_u16(vreinterpretq_u16_s16(row0_lz), 0);
unsigned int nbits = 16 - lz;
/* Emit Huffman-coded symbol and additional diff bits. */
unsigned int diff = vgetq_lane_u16(row0_diff, 0);
PUT_CODE(dctbl->ehufco[nbits], dctbl->ehufsi[nbits], diff)
/* Encode AC coefficients. */
unsigned int r = 0; /* r = run length of zeros */
unsigned int i = 1; /* i = number of coefficients encoded */
/* Code and size information for a run length of 16 zero coefficients */
const unsigned int code_0xf0 = actbl->ehufco[0xf0];
const unsigned int size_0xf0 = actbl->ehufsi[0xf0];
/* The most efficient method of computing nbits and diff depends on the
* number of non-zero coefficients. If the bitmap is not too sparse (> 8
* non-zero AC coefficients), it is beneficial to do all of the work using
* Neon; else we do some of the work using Neon and the rest on demand using
* scalar code.
*/
if (non_zero_coefficients > 8) {
uint8_t block_nbits[DCTSIZE2];
int16x8_t abs_row1 = vabsq_s16(row1);
int16x8_t abs_row2 = vabsq_s16(row2);
int16x8_t abs_row3 = vabsq_s16(row3);
int16x8_t abs_row4 = vabsq_s16(row4);
int16x8_t abs_row5 = vabsq_s16(row5);
int16x8_t abs_row6 = vabsq_s16(row6);
int16x8_t abs_row7 = vabsq_s16(row7);
int16x8_t row1_lz = vclzq_s16(abs_row1);
int16x8_t row2_lz = vclzq_s16(abs_row2);
int16x8_t row3_lz = vclzq_s16(abs_row3);
int16x8_t row4_lz = vclzq_s16(abs_row4);
int16x8_t row5_lz = vclzq_s16(abs_row5);
int16x8_t row6_lz = vclzq_s16(abs_row6);
int16x8_t row7_lz = vclzq_s16(abs_row7);
/* Narrow leading zero count to 8 bits. */
uint8x16_t row01_lz = vuzp1q_u8(vreinterpretq_u8_s16(row0_lz),
vreinterpretq_u8_s16(row1_lz));
uint8x16_t row23_lz = vuzp1q_u8(vreinterpretq_u8_s16(row2_lz),
vreinterpretq_u8_s16(row3_lz));
uint8x16_t row45_lz = vuzp1q_u8(vreinterpretq_u8_s16(row4_lz),
vreinterpretq_u8_s16(row5_lz));
uint8x16_t row67_lz = vuzp1q_u8(vreinterpretq_u8_s16(row6_lz),
vreinterpretq_u8_s16(row7_lz));
/* Compute nbits needed to specify magnitude of each coefficient. */
uint8x16_t row01_nbits = vsubq_u8(vdupq_n_u8(16), row01_lz);
uint8x16_t row23_nbits = vsubq_u8(vdupq_n_u8(16), row23_lz);
uint8x16_t row45_nbits = vsubq_u8(vdupq_n_u8(16), row45_lz);
uint8x16_t row67_nbits = vsubq_u8(vdupq_n_u8(16), row67_lz);
/* Store nbits. */
vst1q_u8(block_nbits + 0 * DCTSIZE, row01_nbits);
vst1q_u8(block_nbits + 2 * DCTSIZE, row23_nbits);
vst1q_u8(block_nbits + 4 * DCTSIZE, row45_nbits);
vst1q_u8(block_nbits + 6 * DCTSIZE, row67_nbits);
/* Mask bits not required to specify sign and amplitude of diff. */
uint16x8_t row1_mask = vshlq_u16(vcltzq_s16(row1), vnegq_s16(row1_lz));
uint16x8_t row2_mask = vshlq_u16(vcltzq_s16(row2), vnegq_s16(row2_lz));
uint16x8_t row3_mask = vshlq_u16(vcltzq_s16(row3), vnegq_s16(row3_lz));
uint16x8_t row4_mask = vshlq_u16(vcltzq_s16(row4), vnegq_s16(row4_lz));
uint16x8_t row5_mask = vshlq_u16(vcltzq_s16(row5), vnegq_s16(row5_lz));
uint16x8_t row6_mask = vshlq_u16(vcltzq_s16(row6), vnegq_s16(row6_lz));
uint16x8_t row7_mask = vshlq_u16(vcltzq_s16(row7), vnegq_s16(row7_lz));
/* diff = abs(coeff) ^ sign(coeff) [no-op for positive coefficients] */
uint16x8_t row1_diff = veorq_u16(vreinterpretq_u16_s16(abs_row1),
row1_mask);
uint16x8_t row2_diff = veorq_u16(vreinterpretq_u16_s16(abs_row2),
row2_mask);
uint16x8_t row3_diff = veorq_u16(vreinterpretq_u16_s16(abs_row3),
row3_mask);
uint16x8_t row4_diff = veorq_u16(vreinterpretq_u16_s16(abs_row4),
row4_mask);
uint16x8_t row5_diff = veorq_u16(vreinterpretq_u16_s16(abs_row5),
row5_mask);
uint16x8_t row6_diff = veorq_u16(vreinterpretq_u16_s16(abs_row6),
row6_mask);
uint16x8_t row7_diff = veorq_u16(vreinterpretq_u16_s16(abs_row7),
row7_mask);
/* Store diff bits. */
vst1q_u16(block_diff + 0 * DCTSIZE, row0_diff);
vst1q_u16(block_diff + 1 * DCTSIZE, row1_diff);
vst1q_u16(block_diff + 2 * DCTSIZE, row2_diff);
vst1q_u16(block_diff + 3 * DCTSIZE, row3_diff);
vst1q_u16(block_diff + 4 * DCTSIZE, row4_diff);
vst1q_u16(block_diff + 5 * DCTSIZE, row5_diff);
vst1q_u16(block_diff + 6 * DCTSIZE, row6_diff);
vst1q_u16(block_diff + 7 * DCTSIZE, row7_diff);
while (bitmap != 0) {
r = BUILTIN_CLZLL(bitmap);
i += r;
bitmap <<= r;
nbits = block_nbits[i];
diff = block_diff[i];
while (r > 15) {
/* If run length > 15, emit special run-length-16 codes. */
PUT_BITS(code_0xf0, size_0xf0)
r -= 16;
}
/* Emit Huffman symbol for run length / number of bits. (F.1.2.2.1) */
unsigned int rs = (r << 4) + nbits;
PUT_CODE(actbl->ehufco[rs], actbl->ehufsi[rs], diff)
i++;
bitmap <<= 1;
}
} else if (bitmap != 0) {
uint16_t block_abs[DCTSIZE2];
/* Compute and store absolute value of coefficients. */
int16x8_t abs_row1 = vabsq_s16(row1);
int16x8_t abs_row2 = vabsq_s16(row2);
int16x8_t abs_row3 = vabsq_s16(row3);
int16x8_t abs_row4 = vabsq_s16(row4);
int16x8_t abs_row5 = vabsq_s16(row5);
int16x8_t abs_row6 = vabsq_s16(row6);
int16x8_t abs_row7 = vabsq_s16(row7);
vst1q_u16(block_abs + 0 * DCTSIZE, vreinterpretq_u16_s16(abs_row0));
vst1q_u16(block_abs + 1 * DCTSIZE, vreinterpretq_u16_s16(abs_row1));
vst1q_u16(block_abs + 2 * DCTSIZE, vreinterpretq_u16_s16(abs_row2));
vst1q_u16(block_abs + 3 * DCTSIZE, vreinterpretq_u16_s16(abs_row3));
vst1q_u16(block_abs + 4 * DCTSIZE, vreinterpretq_u16_s16(abs_row4));
vst1q_u16(block_abs + 5 * DCTSIZE, vreinterpretq_u16_s16(abs_row5));
vst1q_u16(block_abs + 6 * DCTSIZE, vreinterpretq_u16_s16(abs_row6));
vst1q_u16(block_abs + 7 * DCTSIZE, vreinterpretq_u16_s16(abs_row7));
/* Compute diff bits (without nbits mask) and store. */
uint16x8_t row1_diff = veorq_u16(vreinterpretq_u16_s16(abs_row1),
vcltzq_s16(row1));
uint16x8_t row2_diff = veorq_u16(vreinterpretq_u16_s16(abs_row2),
vcltzq_s16(row2));
uint16x8_t row3_diff = veorq_u16(vreinterpretq_u16_s16(abs_row3),
vcltzq_s16(row3));
uint16x8_t row4_diff = veorq_u16(vreinterpretq_u16_s16(abs_row4),
vcltzq_s16(row4));
uint16x8_t row5_diff = veorq_u16(vreinterpretq_u16_s16(abs_row5),
vcltzq_s16(row5));
uint16x8_t row6_diff = veorq_u16(vreinterpretq_u16_s16(abs_row6),
vcltzq_s16(row6));
uint16x8_t row7_diff = veorq_u16(vreinterpretq_u16_s16(abs_row7),
vcltzq_s16(row7));
vst1q_u16(block_diff + 0 * DCTSIZE, row0_diff);
vst1q_u16(block_diff + 1 * DCTSIZE, row1_diff);
vst1q_u16(block_diff + 2 * DCTSIZE, row2_diff);
vst1q_u16(block_diff + 3 * DCTSIZE, row3_diff);
vst1q_u16(block_diff + 4 * DCTSIZE, row4_diff);
vst1q_u16(block_diff + 5 * DCTSIZE, row5_diff);
vst1q_u16(block_diff + 6 * DCTSIZE, row6_diff);
vst1q_u16(block_diff + 7 * DCTSIZE, row7_diff);
/* Same as above but must mask diff bits and compute nbits on demand. */
while (bitmap != 0) {
r = BUILTIN_CLZLL(bitmap);
i += r;
bitmap <<= r;
lz = BUILTIN_CLZ(block_abs[i]);
nbits = 32 - lz;
diff = ((unsigned int)block_diff[i] << lz) >> lz;
while (r > 15) {
/* If run length > 15, emit special run-length-16 codes. */
PUT_BITS(code_0xf0, size_0xf0)
r -= 16;
}
/* Emit Huffman symbol for run length / number of bits. (F.1.2.2.1) */
unsigned int rs = (r << 4) + nbits;
PUT_CODE(actbl->ehufco[rs], actbl->ehufsi[rs], diff)
i++;
bitmap <<= 1;
}
}
/* If the last coefficient(s) were zero, emit an end-of-block (EOB) code.
* The value of RS for the EOB code is 0.
*/
if (i != 64) {
PUT_BITS(actbl->ehufco[0], actbl->ehufsi[0])
}
state_ptr->cur.put_buffer = put_buffer;
state_ptr->cur.free_bits = free_bits;
return buffer;
}
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