add.uw

Add unsigned word

This instruction is defined by:

anyOf:
- B, version >= B@1.0.0
- Zba, version >= Zba@1.0.0

This instruction is included in the following profiles:

RVA22U64 (Mandatory)
RVA23U64 (Mandatory)
RVB23U64 (Mandatory)

Encoding

Assembly format

add.uw rd, rs1, rs2

Synopsis

This instruction performs an XLEN-wide addition between rs2 and the zero-extended least-significant word of rs1.

Access

M	HS	U	VS	VU
Always	Always	Always	Always	Always

Always

Decode Variables

Bits<5> rs2 = $encoding[24:20];
Bits<5> rs1 = $encoding[19:15];
Bits<5> rd = $encoding[11:7];

idl

Execution

IDL
Sail

if (implemented?(ExtensionName::B) && (CSR[misa].B == 1'b0)) {
  raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
X[rd] = X[rs2] + X[rs1][31:0];

idl

{
  let rs1_val = X(rs1);
  let rs2_val = X(rs2);
  let shamt : bits(2) = match op {
    RISCV_ADDUW    => 0b00,
    RISCV_SH1ADDUW => 0b01,
    RISCV_SH2ADDUW => 0b10,
    RISCV_SH3ADDUW => 0b11
  };
  let result : xlenbits = (zero_extend(rs1_val[31..0]) << shamt) + rs2_val;
  X(rd) = result;
  RETIRE_SUCCESS
}

sail

Exceptions

This instruction may result in the following synchronous exceptions:

IllegalInstruction