//
// arch/x86_64/rsp/vrsq.c
//
// This file is subject to the terms and conditions defined in
// 'LICENSE', which is part of this source code package.
//

#include "common.h"
#include "common/reciprocal.h"
#include "rsp/cpu.h"
#include "rsp/rsp.h"
#include <string.h>

// Mask table for vrsq(LH) functions.
cen64_align(static const uint16_t vrsq_mask_table[8][8], 16) = {
  {~0, 0, 0, 0, 0, 0, 0, 0},
  {0, ~0, 0, 0, 0, 0, 0, 0},
  {0, 0, ~0, 0, 0, 0, 0, 0},
  {0, 0, 0, ~0, 0, 0, 0, 0},
  {0, 0, 0, 0, ~0, 0, 0, 0},
  {0, 0, 0, 0, 0, ~0, 0, 0},
  {0, 0, 0, 0, 0, 0, ~0, 0},
  {0, 0, 0, 0, 0, 0, 0, ~0}
};

__m128i rsp_vrsq(struct rsp *rsp, int dp,
  unsigned src, unsigned e, unsigned dest, unsigned de) {
  uint32_t dp_input, sp_input;
  int32_t input, result;
  int16_t vt;

  int32_t input_mask, data;
  unsigned shift, idx;

  // Get the element from VT.
  vt = rsp->cp2.regs[src].e[e & 0x7];

  dp_input = ((uint32_t) rsp->cp2.div_in << 16) | (uint16_t) vt;
  sp_input = vt;

  input = (dp) ? dp_input : sp_input;
  input_mask = input >> 31;
  data = input ^ input_mask;

  if (input > -32768)
    data -= input_mask;

  // Handle edge cases.
  if (data == 0)
    result = 0x7fffFFFFU;

  else if (input == -32768)
    result = 0xffff0000U;

  // Main case: compute the reciprocal.
  else {

    //TODO: Clean this up.
#ifdef _MSC_VER
    unsigned long bsf_index;
    _BitScanReverse(&bsf_index, data);
    shift = 31 - bsf_index;
#else
    shift = __builtin_clz(data);
#endif

    idx = (((unsigned long long) data << shift) & 0x7FC00000U) >> 22;
    idx = ((idx | 0x200) & 0x3FE) | (shift % 2);
    result = rsp_reciprocal_rom[idx];

    result = ((0x10000 | result) << 14) >> ((31 - shift) >> 1);
    result = result ^ input_mask;
  }

  // Write out the results.
  rsp->cp2.div_out = result >> 16;
  rsp->cp2.regs[dest].e[de & 0x7] = result;

  return rsp_vect_load_unshuffled_operand(rsp->cp2.regs[dest].e);
}

__m128i rsp_vrsqh(struct rsp *rsp,
  unsigned src, unsigned e, unsigned dest, unsigned de) {
  __m128i vd, vd_mask, b_result;

  int16_t elements[8];

  // Get the element from VT.
  memcpy(elements, rsp->cp2.regs + src, sizeof(elements));
  rsp->cp2.div_in = elements[e];

  // Write out the upper part of the result.
  vd_mask = _mm_load_si128((__m128i *) vrsq_mask_table[de]);
  vd = _mm_load_si128((__m128i *) (rsp->cp2.regs + dest));
  vd = _mm_andnot_si128(vd_mask, vd);

  b_result = _mm_set1_epi16(rsp->cp2.div_out);
  b_result = _mm_and_si128(vd_mask, b_result);
  return _mm_or_si128(b_result, vd);
}