vfrsub.vf

No synopsis available.

This instruction is defined by:

V, version >= 0

This instruction is included in the following profiles:

RVA22U64 (Optional)

Encoding

Assembly format

vfrsub.vf vm, vs2, rs1, vd

Synopsis

No description available.

Access

M	HS	U	VS	VU
Always	Always	Always	Always	Always

Always

Decode Variables

Bits<1> vm = $encoding[25];
Bits<5> vs2 = $encoding[24:20];
Bits<5> rs1 = $encoding[19:15];
Bits<5> vd = $encoding[11:7];

Execution

IDL
Sail

{
  let rm_3b    = fcsr.FRM();
  let SEW      = get_sew();
  let LMUL_pow = get_lmul_pow();
  let num_elem = get_num_elem(LMUL_pow, SEW);

  if illegal_fp_normal(vd, vm, SEW, rm_3b) then { handle_illegal(); return RETIRE_FAIL };
  assert(SEW != 8);

  let 'n = num_elem;
  let 'm = SEW;

  let vm_val  : vector('n, dec, bool)     = read_vmask(num_elem, vm, 0b00000);
  let rs1_val : bits('m)                  = get_scalar_fp(rs1, 'm);
  let vs2_val : vector('n, dec, bits('m)) = read_vreg(num_elem, SEW, LMUL_pow, vs2);
  let vd_val  : vector('n, dec, bits('m)) = read_vreg(num_elem, SEW, LMUL_pow, vd);
  result      : vector('n, dec, bits('m)) = undefined;
  mask        : vector('n, dec, bool)     = undefined;

  (result, mask) = init_masked_result(num_elem, SEW, LMUL_pow, vd_val, vm_val);

  foreach (i from 0 to (num_elem - 1)) {
    if mask[i] then {
      result[i] = match funct6 {
        VF_VADD          => fp_add(rm_3b, vs2_val[i], rs1_val),
        VF_VSUB          => fp_sub(rm_3b, vs2_val[i], rs1_val),
        VF_VRSUB         => fp_sub(rm_3b, rs1_val, vs2_val[i]),
        VF_VMIN          => fp_min(vs2_val[i], rs1_val),
        VF_VMAX          => fp_max(vs2_val[i], rs1_val),
        VF_VMUL          => fp_mul(rm_3b, vs2_val[i], rs1_val),
        VF_VDIV          => fp_div(rm_3b, vs2_val[i], rs1_val),
        VF_VRDIV         => fp_div(rm_3b, rs1_val, vs2_val[i]),
        VF_VSGNJ         => [rs1_val['m - 1]] @ vs2_val[i][('m - 2)..0],
        VF_VSGNJN        => (0b1 ^ [rs1_val['m - 1]]) @ vs2_val[i][('m - 2)..0],
        VF_VSGNJX        => ([vs2_val[i]['m - 1]] ^ [rs1_val['m - 1]]) @ vs2_val[i][('m - 2)..0],
        VF_VSLIDE1UP     => {
                              if vs2 == vd then { handle_illegal(); return RETIRE_FAIL };
                              if i == 0 then rs1_val else vs2_val[i - 1]
                            },
        VF_VSLIDE1DOWN   => {
                              let last_elem = get_end_element();
                              assert(last_elem < num_elem);
                              if i < last_elem then vs2_val[i + 1] else rs1_val
                            }
      }
    }
  };

  write_vreg(num_elem, SEW, LMUL_pow, vd, result);
  vstart = zeros();
  RETIRE_SUCCESS
}