Count trailing zeros
This instruction determines the number of consecutive binary zero bits, starting from the least significant bit in the source register, and places the result in the destination register.
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| sf | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | Rn | Rd | ||||||||
| S | opcode2 | opcode | |||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_CSSC) then EndOfDecode(Decode_UNDEF); end; let datasize : integer{} = 32 << UInt(sf); let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn);
| <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 = CountLeadingZeroBits(BitReverse{datasize}(operand1)); X{datasize}(d) = result[datasize-1:0];
This instruction is a data-independent-time instruction as described in About PSTATE.DIT.
2026-03_rel 2026-03-26 20:48:11
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