mret

Machine Exception Return

This instruction is defined by:

Encoding

svg

Synopsis

Returns from an exception in M-mode.

Access

M

HS

U

VS

VU

Always

Never

Never

Never

Never

Decode Variables

Execution

  • Pruned, XLEN == 64

  • Original

if (mstatus.MPP != 2'b11) {
  mstatus.MPRV = 0;
}

mstatus.MIE = mstatus.MPIE;
mstatus.MPIE = 1;
if (mstatus.MPP == 2'b00) {
  set_mode(PrivilegeMode::U);
} else if (mstatus.MPP == 2'b01) {
  set_mode(PrivilegeMode::S);
} else if (mstatus.MPP == 2'b11) {
  set_mode(PrivilegeMode::M);
}
mstatus.MPP = 2'b00;
$pc = $bits(mepc);
if (mstatus.MPP != 2'b11) {
  mstatus.MPRV = 0;
}
if (implemented?(ExtensionName::Smdbltrp)) {
  if (xlen() == 64) {
    mstatus.MDT = 1'b0;
  } else {
    mstatush.MDT = 1'b0;
  }
}
mstatus.MIE = mstatus.MPIE;
mstatus.MPIE = 1;
if (mstatus.MPP == 2'b00) {
  set_mode(PrivilegeMode::U);
} else if (mstatus.MPP == 2'b01) {
  set_mode(PrivilegeMode::S);
} else if (mstatus.MPP == 2'b11) {
  set_mode(PrivilegeMode::M);
}
mstatus.MPP = implemented?(ExtensionName::U) ? 2'b00 : 2'b11;
$pc = $bits(mepc);