vssub.vv

No synopsis available.

This instruction is defined by:

V, version >= 0

This instruction is included in the following profiles:

RVA22U64 (Optional)

Encoding

Assembly format

vssub.vv vm, vs2, vs1, 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> vs1 = $encoding[19:15];
Bits<5> vd = $encoding[11:7];

Execution

IDL
Sail

{
  let SEW_pow  = get_sew_pow();
  let SEW      = get_sew();
  let LMUL_pow = get_lmul_pow();
  let VLEN_pow = get_vlen_pow();
  let num_elem = get_num_elem(LMUL_pow, SEW);

  if illegal_normal(vd, vm) then { handle_illegal(); return RETIRE_FAIL };

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

  let vm_val  : vector('n, dec, bool)     = read_vmask(num_elem, vm, 0b00000);
  let vs1_val : vector('n, dec, bits('m)) = read_vreg(num_elem, SEW, LMUL_pow, vs1);
  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 {
        VV_VADD          => vs2_val[i] + vs1_val[i],
        VV_VSUB          => vs2_val[i] - vs1_val[i],
        VV_VAND          => vs2_val[i] & vs1_val[i],
        VV_VOR           => vs2_val[i] | vs1_val[i],
        VV_VXOR          => vs2_val[i] ^ vs1_val[i],
        VV_VSADDU        => unsigned_saturation('m, zero_extend('m + 1, vs2_val[i]) + zero_extend('m + 1, vs1_val[i])),
        VV_VSADD         => signed_saturation('m, sign_extend('m + 1, vs2_val[i]) + sign_extend('m + 1, vs1_val[i])),
        VV_VSSUBU        => {
                              if unsigned(vs2_val[i]) < unsigned(vs1_val[i]) then zeros()
                              else unsigned_saturation('m, zero_extend('m + 1, vs2_val[i]) - zero_extend('m + 1, vs1_val[i]))
                            },
        VV_VSSUB         => signed_saturation('m, sign_extend('m + 1, vs2_val[i]) - sign_extend('m + 1, vs1_val[i])),
        VV_VSMUL         => {
                              let result_mul = to_bits('m * 2, signed(vs2_val[i]) * signed(vs1_val[i]));
                              let rounding_incr = get_fixed_rounding_incr(result_mul, 'm - 1);
                              let result_wide = (result_mul >> ('m - 1)) + zero_extend('m * 2, rounding_incr);
                              signed_saturation('m, result_wide['m..0])
                            },
        VV_VSLL          => {
                              let shift_amount = get_shift_amount(vs1_val[i], SEW);
                              vs2_val[i] << shift_amount
                            },
        VV_VSRL          => {
                              let shift_amount = get_shift_amount(vs1_val[i], SEW);
                              vs2_val[i] >> shift_amount
                            },
        VV_VSRA          => {
                              let shift_amount = get_shift_amount(vs1_val[i], SEW);
                              let v_double : bits('m * 2) = sign_extend(vs2_val[i]);
                              slice(v_double >> shift_amount, 0, SEW)
                            },
        VV_VSSRL         => {
                              let shift_amount = get_shift_amount(vs1_val[i], SEW);
                              let rounding_incr = get_fixed_rounding_incr(vs2_val[i], shift_amount);
                              (vs2_val[i] >> shift_amount) + zero_extend('m, rounding_incr)
                            },
        VV_VSSRA         => {
                              let shift_amount = get_shift_amount(vs1_val[i], SEW);
                              let rounding_incr = get_fixed_rounding_incr(vs2_val[i], shift_amount);
                              let v_double : bits('m * 2) = sign_extend(vs2_val[i]);
                              slice(v_double >> shift_amount, 0, SEW) + zero_extend('m, rounding_incr)
                            },
        VV_VMINU         => to_bits(SEW, min(unsigned(vs2_val[i]), unsigned(vs1_val[i]))),
        VV_VMIN          => to_bits(SEW, min(signed(vs2_val[i]), signed(vs1_val[i]))),
        VV_VMAXU         => to_bits(SEW, max(unsigned(vs2_val[i]), unsigned(vs1_val[i]))),
        VV_VMAX          => to_bits(SEW, max(signed(vs2_val[i]), signed(vs1_val[i]))),
        VV_VRGATHER      => {
                              if (vs1 == vd | vs2 == vd) then { handle_illegal(); return RETIRE_FAIL };
                              let idx = unsigned(vs1_val[i]);
                              let VLMAX = int_power(2, LMUL_pow + VLEN_pow - SEW_pow);
                              assert(VLMAX <= 'n);
                              if idx < VLMAX then vs2_val[idx] else zeros()
                            },
        VV_VRGATHEREI16  => {
                              if (vs1 == vd | vs2 == vd) then { handle_illegal(); return RETIRE_FAIL };
                              /* vrgatherei16.vv uses SEW/LMUL for the data in vs2 but EEW=16 and EMUL = (16/SEW)*LMUL for the indices in vs1 */
                              let vs1_new : vector('n, dec, bits(16)) = read_vreg(num_elem, 16, 4 + LMUL_pow - SEW_pow, vs1);
                              let idx = unsigned(vs1_new[i]);
                              let VLMAX = int_power(2, LMUL_pow + VLEN_pow - SEW_pow);
                              assert(VLMAX <= 'n);
                              if idx < VLMAX then vs2_val[idx] else zeros()
                            }
      }
    }
  };

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