src/cksum_pclmul.c

   1 /* cksum -- calculate and print POSIX checksums and sizes of files
   2    Copyright (C) 1992-2024 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 #include <stdio.h>
  20 #include <sys/types.h>
  21 #include <stdint.h>
  22 #include <x86intrin.h>
  23 #include "system.h"
  24
  25 /* Number of bytes to read at once.  */
  26 #define BUFLEN (1 << 16)
  27
  28 extern uint_fast32_t const crctab[8][256];
  29
  30 extern bool
  31 cksum_pclmul (FILE *fp, uint_fast32_t *crc_out, uintmax_t *length_out);
  32
  33 /* Calculate CRC32 using PCLMULQDQ CPU instruction found in x86/x64 CPUs */
  34
  35 bool
  36 cksum_pclmul (FILE *fp, uint_fast32_t *crc_out, uintmax_t *length_out)
  37 {
  38   __m128i buf[BUFLEN / sizeof (__m128i)];
  39   uint_fast32_t crc = 0;
  40   uintmax_t length = 0;
  41   size_t bytes_read;
  42   __m128i single_mult_constant;
  43   __m128i four_mult_constant;
  44   __m128i shuffle_constant;
  45
  46   if (!fp || !crc_out || !length_out)
  47     return false;
  48
  49   /* These constants and general algorithms are taken from the Intel whitepaper
  50      "Fast CRC Computation for Generic Polynomials Using PCLMULQDQ Instruction"
  51   */
  52   single_mult_constant = _mm_set_epi64x (0xC5B9CD4C, 0xE8A45605);
  53   four_mult_constant = _mm_set_epi64x (0x8833794C, 0xE6228B11);
  54
  55   /* Constant to byteswap a full SSE register */
  56   shuffle_constant = _mm_set_epi8 (0, 1, 2, 3, 4, 5, 6, 7, 8,
  57                                    9, 10, 11, 12, 13, 14, 15);
  58
  59   while ((bytes_read = fread (buf, 1, BUFLEN, fp)) > 0)
  60     {
  61       __m128i *datap;
  62       __m128i data;
  63       __m128i data2;
  64       __m128i data3;
  65       __m128i data4;
  66       __m128i data5;
  67       __m128i data6;
  68       __m128i data7;
  69       __m128i data8;
  70       __m128i fold_data;
  71       __m128i xor_crc;
  72
  73       if (length + bytes_read < length)
  74         {
  75           errno = EOVERFLOW;
  76           return false;
  77         }
  78       length += bytes_read;
  79
  80       datap = (__m128i *)buf;
  81
  82       /* Fold in parallel eight 16-byte blocks into four 16-byte blocks */
  83       if (bytes_read >= 16 * 8)
  84         {
  85           data = _mm_loadu_si128 (datap);
  86           data = _mm_shuffle_epi8 (data, shuffle_constant);
  87           /* XOR in initial CRC value (for us 0 so no effect), or CRC value
  88              calculated for previous BUFLEN buffer from fread */
  89           xor_crc = _mm_set_epi32 (crc, 0, 0, 0);
  90           crc = 0;
  91           data = _mm_xor_si128 (data, xor_crc);
  92           data3 = _mm_loadu_si128 (datap + 1);
  93           data3 = _mm_shuffle_epi8 (data3, shuffle_constant);
  94           data5 = _mm_loadu_si128 (datap + 2);
  95           data5 = _mm_shuffle_epi8 (data5, shuffle_constant);
  96           data7 = _mm_loadu_si128 (datap + 3);
  97           data7 = _mm_shuffle_epi8 (data7, shuffle_constant);
  98
  99
 100           while (bytes_read >= 16 * 8)
 101             {
 102               datap += 4;
 103
 104               /* Do multiplication here for four consecutive 16 byte blocks */
 105               data2 = _mm_clmulepi64_si128 (data, four_mult_constant, 0x00);
 106               data = _mm_clmulepi64_si128 (data, four_mult_constant, 0x11);
 107               data4 = _mm_clmulepi64_si128 (data3, four_mult_constant, 0x00);
 108               data3 = _mm_clmulepi64_si128 (data3, four_mult_constant, 0x11);
 109               data6 = _mm_clmulepi64_si128 (data5, four_mult_constant, 0x00);
 110               data5 = _mm_clmulepi64_si128 (data5, four_mult_constant, 0x11);
 111               data8 = _mm_clmulepi64_si128 (data7, four_mult_constant, 0x00);
 112               data7 = _mm_clmulepi64_si128 (data7, four_mult_constant, 0x11);
 113
 114               /* Now multiplication results for the four blocks is xor:ed with
 115                  next four 16 byte blocks from the buffer. This effectively
 116                  "consumes" the first four blocks from the buffer.
 117                  Keep xor result in variables for multiplication in next
 118                  round of loop. */
 119               data = _mm_xor_si128 (data, data2);
 120               data2 = _mm_loadu_si128 (datap);
 121               data2 = _mm_shuffle_epi8 (data2, shuffle_constant);
 122               data = _mm_xor_si128 (data, data2);
 123
 124               data3 = _mm_xor_si128 (data3, data4);
 125               data4 = _mm_loadu_si128 (datap + 1);
 126               data4 = _mm_shuffle_epi8 (data4, shuffle_constant);
 127               data3 = _mm_xor_si128 (data3, data4);
 128
 129               data5 = _mm_xor_si128 (data5, data6);
 130               data6 = _mm_loadu_si128 (datap + 2);
 131               data6 = _mm_shuffle_epi8 (data6, shuffle_constant);
 132               data5 = _mm_xor_si128 (data5, data6);
 133
 134               data7 = _mm_xor_si128 (data7, data8);
 135               data8 = _mm_loadu_si128 (datap + 3);
 136               data8 = _mm_shuffle_epi8 (data8, shuffle_constant);
 137               data7 = _mm_xor_si128 (data7, data8);
 138
 139               bytes_read -= (16 * 4);
 140             }
 141           /* At end of loop we write out results from variables back into
 142              the buffer, for use in single fold loop */
 143           data = _mm_shuffle_epi8 (data, shuffle_constant);
 144           _mm_storeu_si128 (datap, data);
 145           data3 = _mm_shuffle_epi8 (data3, shuffle_constant);
 146           _mm_storeu_si128 (datap + 1, data3);
 147           data5 = _mm_shuffle_epi8 (data5, shuffle_constant);
 148           _mm_storeu_si128 (datap + 2, data5);
 149           data7 = _mm_shuffle_epi8 (data7, shuffle_constant);
 150           _mm_storeu_si128 (datap + 3, data7);
 151         }
 152
 153       /* Fold two 16-byte blocks into one 16-byte block */
 154       if (bytes_read >= 32)
 155         {
 156           data = _mm_loadu_si128 (datap);
 157           data = _mm_shuffle_epi8 (data, shuffle_constant);
 158           xor_crc = _mm_set_epi32 (crc, 0, 0, 0);
 159           crc = 0;
 160           data = _mm_xor_si128 (data, xor_crc);
 161           while (bytes_read >= 32)
 162             {
 163               datap++;
 164
 165               data2 = _mm_clmulepi64_si128 (data, single_mult_constant, 0x00);
 166               data = _mm_clmulepi64_si128 (data, single_mult_constant, 0x11);
 167               fold_data = _mm_loadu_si128 (datap);
 168               fold_data = _mm_shuffle_epi8 (fold_data, shuffle_constant);
 169               data = _mm_xor_si128 (data, data2);
 170               data = _mm_xor_si128 (data, fold_data);
 171               bytes_read -= 16;
 172             }
 173           data = _mm_shuffle_epi8 (data, shuffle_constant);
 174           _mm_storeu_si128 (datap, data);
 175         }
 176
 177       /* And finish up last 0-31 bytes in a byte by byte fashion */
 178       unsigned char *cp = (unsigned char *)datap;
 179       while (bytes_read--)
 180         crc = (crc << 8) ^ crctab[0][((crc >> 24) ^ *cp++) & 0xFF];
 181       if (feof (fp))
 182         break;
 183     }
 184
 185   *crc_out = crc;
 186   *length_out = length;
 187
 188   return !ferror (fp);
 189 }