tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
Log | Files | Refs | README | LICENSE

CharacterDataBufferVMX.cpp (3327B)

      1 /* This Source Code Form is subject to the terms of the Mozilla Public
      2 * License, v. 2.0. If a copy of the MPL was not distributed with this
      3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      4 
      5 // This file should only be compiled if you're on Power ISA.
      6 
      7 #include <altivec.h>
      8 
      9 #include <algorithm>
     10 
     11 #include "CharacterDataBufferImpl.h"
     12 #include "mozilla/Assertions.h"
     13 #include "nscore.h"
     14 
     15 namespace mozilla {
     16 namespace VMX {
     17 
     18 int32_t FirstNon8Bit(const char16_t* str, const char16_t* end) {
     19  const uint32_t numUnicharsPerVector = 8;
     20  const uint32_t numCharsPerVector = 16;
     21  // Paranoia. If this assertion is wrong, change the vector loop below.
     22  MOZ_ASSERT((numCharsPerVector / numUnicharsPerVector) == sizeof(char16_t));
     23 
     24  typedef Non8BitParameters<sizeof(size_t)> p;
     25  const uint32_t alignMask = p::alignMask();
     26  const size_t mask = p::mask();
     27  const uint32_t numUnicharsPerWord = p::numUnicharsPerWord();
     28 
     29  const uint32_t len = end - str;
     30 
     31  // i shall count the index in unichars; i2 shall count the index in chars.
     32  uint32_t i = 0;
     33  uint32_t i2 = 0;
     34 
     35  // Align ourselves to a 16-byte boundary, as required by VMX loads.
     36  uint32_t alignLen = std::min(
     37      len, uint32_t(((-NS_PTR_TO_UINT32(str)) & 0xf) / sizeof(char16_t)));
     38 
     39  if ((len - alignLen) >= numUnicharsPerVector) {
     40    for (; i < alignLen; i++) {
     41      if (str[i] > 255) return i;
     42    }
     43 
     44    // Construct a vector of shorts.
     45 #if __LITTLE_ENDIAN__
     46    const vector unsigned short gtcompare =
     47        reinterpret_cast<vector unsigned short>(
     48            vec_mergel(vec_splat_s8(-1), vec_splat_s8(0)));
     49 #else
     50    const vector unsigned short gtcompare =
     51        reinterpret_cast<vector unsigned short>(
     52            vec_mergel(vec_splat_s8(0), vec_splat_s8(-1)));
     53 #endif
     54    const uint32_t vectWalkEnd =
     55        ((len - i) / numUnicharsPerVector) * numUnicharsPerVector;
     56    i2 = i * sizeof(char16_t);
     57 
     58    while (1) {
     59      vector unsigned short vect;
     60 
     61      // Check one VMX register (8 unichars) at a time. The vec_any_gt
     62      // intrinsic does exactly what we want. This loop is manually unrolled;
     63      // it yields notable performance improvements this way.
     64 #define CheckForASCII                                              \
     65  vect = vec_ld(i2, reinterpret_cast<const unsigned short*>(str)); \
     66  if (vec_any_gt(vect, gtcompare)) return i;                       \
     67  i += numUnicharsPerVector;                                       \
     68  if (!(i < vectWalkEnd)) break;                                   \
     69  i2 += numCharsPerVector;
     70 
     71      CheckForASCII CheckForASCII
     72 
     73 #undef CheckForASCII
     74    }
     75  } else {
     76    // Align ourselves to a word boundary.
     77    alignLen = std::min(len, uint32_t(((-NS_PTR_TO_UINT32(str)) & alignMask) /
     78                                      sizeof(char16_t)));
     79    for (; i < alignLen; i++) {
     80      if (str[i] > 255) return i;
     81    }
     82  }
     83 
     84  // Check one word at a time.
     85  const uint32_t wordWalkEnd =
     86      ((len - i) / numUnicharsPerWord) * numUnicharsPerWord;
     87  for (; i < wordWalkEnd; i += numUnicharsPerWord) {
     88    const size_t word = *reinterpret_cast<const size_t*>(str + i);
     89    if (word & mask) return i;
     90  }
     91 
     92  // Take care of the remainder one character at a time.
     93  for (; i < len; i++) {
     94    if (str[i] > 255) {
     95      return i;
     96    }
     97  }
     98 
     99  return -1;
    100 }
    101 
    102 }  // namespace VMX
    103 }  // namespace mozilla