sh1add

Shift left by 1 and add

This instruction is defined by:

anyOf:
- B, version >= 0
- Zba, version >= 0

This instruction is included in the following profiles:

RVA22S64 (Mandatory)
RVA22U64 (Mandatory)

Encoding

Assembly format

sh1add rd, rs1, rs2

Synopsis

This instruction shifts rs1 to the left by 1 bit and adds it to rs2.

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];

Execution

IDL
Sail

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

{
  let rs1_val = X(rs1);
  let rs2_val = X(rs2);
  let shamt : bits(2) = match op {
    RISCV_SH1ADD => 0b01,
    RISCV_SH2ADD => 0b10,
    RISCV_SH3ADD => 0b11
  };
  let result : xlenbits = (rs1_val << shamt) + rs2_val;
  X(rd) = result;
  RETIRE_SUCCESS
}

Exceptions

This instruction may result in the following synchronous exceptions:

IllegalInstruction