srai

Shift right arithmetic immediate

This instruction is defined by:

  • I, version >= I@2.1.0

This instruction is included in the following profiles:

  • MockProfile 64-bit S-mode (Mandatory)

  • MockProfile 64-bit Unpriv (Mandatory)

  • RVA20S64 (Mandatory)

  • RVA20U64 (Mandatory)

  • RVA22S64 (Mandatory)

  • RVA22U64 (Mandatory)

  • RVA23M64 (Mandatory)

  • RVA23S64 (Mandatory)

  • RVA23U64 (Mandatory)

  • RVB23M64 (Mandatory)

  • RVB23S64 (Mandatory)

  • RVB23U64 (Mandatory)

  • RVI20U32 (Mandatory)

  • RVI20U64 (Mandatory)

Encoding

This instruction has different encodings in RV32 and RV64.

  • RV32

  • RV64

svg
svg

Assembly format

srai rd, rs1, shamt

Synopsis

This instruction must have data-independent timing when extension Zkt is enabled.

Arithmetic shift (the original sign bit is copied into the vacated upper bits) the value in xs1 right by shamt, and store the result in xd.

Access

M HS U VS VU

Always

Always

Always

Always

Always

Decode Variables

  • RV32

  • RV64

Bits<5> shamt = $encoding[24:20];
Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];
Bits<6> shamt = $encoding[25:20];
Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];

Execution

  • IDL

  • Sail

X[xd] = X[xs1] >>> shamt;
{
  let xs1_val = X(xs1);
  /* the decoder guaxd should ensure that shamt[5] = 0 for RV32 */
  let result : xlenbits = match op {
    RISCV_SLLI => if   sizeof(xlen) == 32
                  then xs1_val << shamt[4..0]
                  else xs1_val << shamt,
    RISCV_SRLI => if   sizeof(xlen) == 32
                  then xs1_val >> shamt[4..0]
                  else xs1_val >> shamt,
    RISCV_SRAI => if   sizeof(xlen) == 32
                  then shift_right_arith32(xs1_val, shamt[4..0])
                  else shift_right_arith64(xs1_val, shamt)
  };
  X(xd) = result;
  RETIRE_SUCCESS
}