vrsub.vi

No synopsis available.

This instruction is defined by:

V, version >= 0

This instruction is included in the following profiles:

RVA22U64 (Optional)

Encoding

Assembly format

vrsub.vi vm, vs2, vd, imm

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> simm5 = $encoding[19:15];
Bits<5> vd = $encoding[11:7];

Execution

IDL
Sail

{
  let SEW      = get_sew();
  let LMUL_pow = get_lmul_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 imm_val : bits('m)                  = sign_extend(simm);
  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 {
        VI_VADD    => vs2_val[i] + imm_val,
        VI_VRSUB   => imm_val - vs2_val[i],
        VI_VAND    => vs2_val[i] & imm_val,
        VI_VOR     => vs2_val[i] | imm_val,
        VI_VXOR    => vs2_val[i] ^ imm_val,
        VI_VSADDU  => unsigned_saturation('m, zero_extend('m + 1, vs2_val[i]) + zero_extend('m + 1, imm_val) ),
        VI_VSADD   => signed_saturation('m, sign_extend('m + 1, vs2_val[i]) + sign_extend('m + 1, imm_val) ),
        VI_VSLL    => {
                        let shift_amount = get_shift_amount(zero_extend('m, simm), SEW);
                        vs2_val[i] << shift_amount
                      },
        VI_VSRL    => {
                        let shift_amount = get_shift_amount(zero_extend('m, simm), SEW);
                        vs2_val[i] >> shift_amount
                      },
        VI_VSRA    => {
                        let shift_amount = get_shift_amount(zero_extend('m, simm), SEW);
                        let v_double : bits('m * 2) = sign_extend(vs2_val[i]);
                        slice(v_double >> shift_amount, 0, SEW)
                      },
        VI_VSSRL   => {
                        let shift_amount = get_shift_amount(zero_extend('m, simm), SEW);
                        let rounding_incr = get_fixed_rounding_incr(vs2_val[i], shift_amount);
                        (vs2_val[i] >> shift_amount) + zero_extend('m, rounding_incr)
                      },
        VI_VSSRA   => {
                        let shift_amount = get_shift_amount(zero_extend('m, simm), 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)
                      }
      }
    }
  };

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