vaesz.adoc

vaesz.vs

Synopsis

Vector AES round zero encryption/decryption

Mnemonic

vaesz.vs vd, vs2

Encoding (Vector-Scalar)

{reg:[
{bits: 7, name: 'OP-P'},
{bits: 5, name: 'vd'},
{bits: 3, name: 'OPMVV'},
{bits: 5, name: '00111'},
{bits: 5, name: 'vs2'},
{bits: 1, name: '1'},
{bits: 6, name: '101001'},
]}

Reserved Encodings

• SEW is any value other than 32

• The vd register group overlaps the vs2 register

Arguments

Register	Direction	EGW	EGS	EEW	Definition
vd	input	128	4	32	round state
vs2	input	128	4	32	round key
vd	output	128	4	32	new round state

Description

A round-0 AES block cipher operation is performed. This operation is used for both encryption and decryption.

There is only a .vs form of the instruction. Vs2 holds a scalar element group that is used as the round key for all of the round state element groups. The new round state output of each element group is produced by XORing the round key with each element group of vd.

This instruction must always be implemented such that its execution latency does not depend on the data being operated upon.

Note

This instruction is needed to avoid the need to "splat" a 128-bit vector register group when the round key is the same for all 128-bit "lanes". Such a splat would typically be implemented with a vrgather instruction which would hurt performance in many implementations. This instruction only exists in the .vs form because the .vv form would be identical to the vxor.vv vd, vs2, vd instruction.

Operation

function clause execute (VAESZ(vs2, vd) = {
  if(((vstart%EGS)<>0) | (LMUL*VLEN < EGW))  then {
    handle_illegal();  // illegal instruction exception
    RETIRE_FAIL
  } else {

  eg_len = (vl/EGS)
  eg_start = (vstart/EGS)

  foreach (i from eg_start to eg_len-1) {
    let state : bits(128) = get_velem(vd, EGW=128, i);
    let rkey  : bits(128) = get_velem(vs2, EGW=128, 0);
    let ark   : bits(128) = state ^ rkey;
    set_velem(vd, EGW=128, i, ark);
  }
  RETIRE_SUCCESS
  }
}

Included in

Extension	Minimum version	Lifecycle state
[zvkned]	v0.1.0	In Development