sse42_skip_opt.nim

when defined(useSSE42):
  import x86_simd/x86_sse42
  import x86_simd/x86_sse41
  import x86_simd/x86_sse2
  import bitops

  let prStr = "azAZ09\x80\xFF\0                 " # padded to hold at least 16 bytes.
  let pcStr = "+,/_:.~()}{@=!-\0                "
  let plain_ranges = loadu_si128(cast[ptr m128i](unsafeAddr prStr[0]))
  let plain_chars = loadu_si128(cast[ptr m128i](unsafeAddr pcStr[0]))

#...

  while true:
    let c = s[i]
    inc i
    case c
    of plain:
      let begin = i-1
      block findPlainRange:
        when defined(useSSE42):
          if s.len-i >= 16:
            while s.len-i >= 16:
              let vec = loadu_si128(cast[ptr m128i](unsafeAddr s[i]))
              const commonFlags = SIDD_NEGATIVE_POLARITY or SIDD_UNIT_MASK
              let rMask = cmpistrm(plain_ranges, vec, SIDD_CMP_RANGES or commonFlags)
              let pMask = cmpistrm(plain_chars, vec, SIDD_CMP_EQUAL_ANY or commonFlags)
              if not testz_si128(rMask, pMask).bool:
                let mask = and_si128(rMask, pMask)
                let bits = movemask_epi8(mask)
                i += bits.countTrailingZeroBits
                break findPlainRange
              i += 16
        while s[i] in plain: inc i
      curStr &= s[begin..<i]
#...