sext.b

Sign-extend byte

Sign-extends the least-significant byte in the source to XLEN by copying the most-significant bit in the byte (i.e., bit 7) to all of the more-significant bits.

Assembly format

sext.b xd, xs1

Decode Variables

Bits<5> xs1 = $encoding[19:15];
Bits<5> xd = $encoding[11:7];

Execution

if (implemented?(ExtensionName::B) && (CSR[misa].B == 1'b0)) {
  raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
if (xlen() == 32) {
  X[xd] = {{24{X[xs1][7]}}, X[xs1][7:0]};
} else if (xlen() == 64) {
  X[xd] = {{56{X[xs1][7]}}, X[xs1][7:0]};
}

Exceptions

This instruction may result in the following synchronous exceptions:

  • IllegalInstruction

Encoding

svg

Defining extension

Zbb

Access

M

Always

Containing profiles

  • Mandatory: RVA22S64, RVA22U64, RVA23S64, RVA23U64, RVB23S64, RVB23U64

  • Optional: None