CLS Count leading sign bits This instruction counts the number of leading bits of the source register that have the same value as the most significant bit of the register, and writes the result to the destination register. This count does not include the most significant bit of the source register. This instruction is a data-independent-time instruction as described in About PSTATE.DIT. 1 0 1 1 0 1 0 1 1 0 0 0 0 0 0 0 0 0 1 0 1 0 CLS <Wd>, <Wn> 1 CLS <Xd>, <Xn> let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let datasize : integer{} = 32 << UInt(sf); <Wd> Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field. <Wn> Is the 32-bit name of the general-purpose source register, encoded in the "Rn" field. <Xd> Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field. <Xn> Is the 64-bit name of the general-purpose source register, encoded in the "Rn" field. let operand1 : bits(datasize) = X{}(n); let result : integer = CountLeadingSignBits(operand1); X{datasize}(d) = result[datasize-1:0]; 2026-03-12 12:23:09 2025-09_rel_asl1