sext.b

Sign-extend byte

This instruction is defined by:

Encoding

Synopsis

This instruction 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.

Access

Always

Decode Variables

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

Execution

Pruned, XLEN == 64
Original

if ((%%LINK%csr_field;misa.B;CSR[misa].B%% == 1'b0)) {
  %%LINK%func;raise;raise%%(ExceptionCode::IllegalInstruction, %%LINK%func;mode;mode%%(), $encoding);
}
X[rd] = {{56{X[rs1][7]}}, X[rs1][7:0]};

if (%%LINK%func;implemented?;implemented?%%(ExtensionName::B) && (%%LINK%csr_field;misa.B;CSR[misa].B%% == 1'b0)) {
  %%LINK%func;raise;raise%%(ExceptionCode::IllegalInstruction, %%LINK%func;mode;mode%%(), $encoding);
}
if (%%LINK%func;xlen;xlen%%() == 32) {
  X[rd] = {{24{X[rs1][7]}}, X[rs1][7:0]};
} else if (%%LINK%func;xlen;xlen%%() == 64) {
  X[rd] = {{56{X[rs1][7]}}, X[rs1][7:0]};
}

Exceptions

This instruction may result in the following synchronous exceptions:

IllegalInstruction