ceph/src/common/crc32c_ppc.c

   1 /* Copyright (C) 2017 International Business Machines Corp.
   2  * All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  */
   9 #define CRC_TABLE
  10 #define FAST_ZERO_TABLE
  11
  12 #include "acconfig.h"
  13 #include "include/int_types.h"
  14 #include "crc32c_ppc_constants.h"
  15 #include "reverse.h"
  16
  17 #include <stdlib.h>
  18 #include <strings.h>
  19
  20 #define VMX_ALIGN       16
  21 #define VMX_ALIGN_MASK  (VMX_ALIGN-1)
  22
  23 #ifdef REFLECT
  24 static unsigned int crc32_align(unsigned int crc, unsigned char const *p,
  25                                 unsigned long len)
  26 {
  27   while (len--)
  28     crc = crc_table[(crc ^ *p++) & 0xff] ^ (crc >> 8);
  29   return crc;
  30 }
  31 #else
  32 static unsigned int crc32_align(unsigned int crc, unsigned char const *p,
  33                                 unsigned long len)
  34 {
  35   while (len--)
  36     crc = crc_table[((crc >> 24) ^ *p++) & 0xff] ^ (crc << 8);
  37   return crc;
  38 }
  39 #endif
  40
  41 #ifdef HAVE_POWER8
  42 static inline unsigned long polynomial_multiply(unsigned int a, unsigned int b) {
  43         vector unsigned int va = {a, 0, 0, 0};
  44         vector unsigned int vb = {b, 0, 0, 0};
  45         vector unsigned long vt;
  46
  47         __asm__("vpmsumw %0,%1,%2" : "=v"(vt) : "v"(va), "v"(vb));
  48
  49         return vt[0];
  50 }
  51
  52 unsigned int barrett_reduction(unsigned long val);
  53
  54 static inline unsigned int gf_multiply(unsigned int a, unsigned int b) {
  55         return barrett_reduction(polynomial_multiply(a, b));
  56 }
  57
  58 unsigned int append_zeros(unsigned int crc, unsigned long length) {
  59         unsigned long i = 0;
  60
  61         while (length) {
  62                 if (length & 1) {
  63                         crc = gf_multiply(crc, crc_zero[i]);
  64                 }
  65                 i++;
  66                 length /= 2;
  67         }
  68
  69         return crc;
  70 }
  71
  72
  73 unsigned int __crc32_vpmsum(unsigned int crc, unsigned char const *p,
  74                             unsigned long len);
  75
  76 static uint32_t crc32_vpmsum(uint32_t crc, unsigned char const *data,
  77                              unsigned len)
  78 {
  79   unsigned int prealign;
  80   unsigned int tail;
  81
  82 #ifdef CRC_XOR
  83   crc ^= 0xffffffff;
  84 #endif
  85
  86   if (len < VMX_ALIGN + VMX_ALIGN_MASK) {
  87     crc = crc32_align(crc, data, (unsigned long)len);
  88     goto out;
  89   }
  90
  91   if ((unsigned long)data & VMX_ALIGN_MASK) {
  92     prealign = VMX_ALIGN - ((unsigned long)data & VMX_ALIGN_MASK);
  93     crc = crc32_align(crc, data, prealign);
  94     len -= prealign;
  95     data += prealign;
  96   }
  97
  98   crc = __crc32_vpmsum(crc, data, (unsigned long)len & ~VMX_ALIGN_MASK);
  99
 100   tail = len & VMX_ALIGN_MASK;
 101   if (tail) {
 102     data += len & ~VMX_ALIGN_MASK;
 103     crc = crc32_align(crc, data, tail);
 104   }
 105
 106 out:
 107 #ifdef CRC_XOR
 108   crc ^= 0xffffffff;
 109 #endif
 110
 111   return crc;
 112 }
 113
 114 /* This wrapper function works around the fact that crc32_vpmsum
 115  * does not gracefully handle the case where the data pointer is NULL.
 116  */
 117 uint32_t ceph_crc32c_ppc(uint32_t crc, unsigned char const *data, unsigned len)
 118 {
 119   if (!data) {
 120     /* Handle the NULL buffer case. */
 121 #ifdef REFLECT
 122     crc = reverse_bits(crc);
 123 #endif
 124
 125     crc = append_zeros(crc, len);
 126
 127 #ifdef REFLECT
 128     crc = reverse_bits(crc);
 129 #endif
 130   } else {
 131     /* Handle the valid buffer case. */
 132     crc = crc32_vpmsum(crc, data, (unsigned long)len);
 133   }
 134   return crc;
 135 }
 136
 137 #else /* HAVE_POWER8 */
 138
 139 /* This symbol has to exist on non-ppc architectures (and on legacy
 140  * ppc systems using power7 or below) in order to compile properly
 141  * there, even though it won't be called.
 142  */
 143 uint32_t ceph_crc32c_ppc(uint32_t crc, unsigned char const *data, unsigned len)
 144 {
 145   return 0;
 146 }
 147
 148 #endif /* HAVE_POWER8 */