C++ 中文周刊 第71期

void remove_negatives(const int32_t *input, int64_t count, int32_t *output) {
  int64_t j = 0;
  const int32_t* endPtr = input + count;
  const uint64_t vl_u32 = svcntw();

  svbool_t all_mask = svptrue_b32();
  while(input <= endPtr - (4*vl_u32))
  {
      svint32_t in0 = svld1_s32(all_mask, input + 0*vl_u32);
      svint32_t in1 = svld1_s32(all_mask, input + 1*vl_u32);
      svint32_t in2 = svld1_s32(all_mask, input + 2*vl_u32);
      svint32_t in3 = svld1_s32(all_mask, input + 3*vl_u32);

      svbool_t pos0 = svcmpge_n_s32(all_mask, in0, 0);
      svbool_t pos1 = svcmpge_n_s32(all_mask, in1, 0);
      svbool_t pos2 = svcmpge_n_s32(all_mask, in2, 0);
      svbool_t pos3 = svcmpge_n_s32(all_mask, in3, 0);

      in0 = svcompact_s32(pos0, in0);
      in1 = svcompact_s32(pos1, in1);
      in2 = svcompact_s32(pos2, in2);
      in3 = svcompact_s32(pos3, in3);

      svst1_s32(all_mask, output + j, in0);
      j += svcntp_b32(all_mask, pos0);
      svst1_s32(all_mask, output + j, in1);
      j += svcntp_b32(all_mask, pos1);
      svst1_s32(all_mask, output + j, in2);
      j += svcntp_b32(all_mask, pos2);
      svst1_s32(all_mask, output + j, in3);
      j += svcntp_b32(all_mask, pos3);

      input += 4*vl_u32;
  }

  int64_t i = 0;
  count = endPtr - input;

  svbool_t while_mask = svwhilelt_b32(i, count);
  do {
    svint32_t in = svld1_s32(while_mask, input + i);
    svbool_t positive = svcmpge_n_s32(while_mask, in, 0);
    svint32_t in_positive = svcompact_s32(positive, in);
    svst1_s32(while_mask, output + j, in_positive);
    i += svcntw();
    j += svcntp_b32(while_mask, positive);
    while_mask = svwhilelt_b32(i, count);
  } while (svptest_any(svptrue_b32(), while_mask));
}

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