bext

Single-Bit extract (Register)

This instruction is defined by:

Encoding

Synopsis

This instruction returns a single bit extracted from rs1 at the index specified in rs2. The index is read from the lower log2(XLEN) bits of rs2.

Access

Always

Decode Variables

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

Execution

Pruned, XLEN == 64
Original

XReg index = X[rs2] & (63);
X[rd] = (X[rs1] >> index) & 1;

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