CLZ Count Leading Zeros Count Leading Zeros returns the number of binary zero bits before the first binary one bit in a value. For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors. If CPSR.DIT is 1, this instruction has passed its condition execution check, and does not use R15 as either its source or destination: The execution time of this instruction is independent of:The values of the data supplied in any of its registers.The values of the NZCV flags. The response of this instruction to asynchronous exceptions does not vary based on:The values of the data supplied in any of its registers.The values of the NZCV flags. It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) . != 1111 0 0 0 1 0 1 1 0 (1) (1) (1) (1) (1) (1) (1) (1) 0 0 0 1 CLZ{<c>}{<q>} <Rd>, <Rm> d = UInt(Rd); m = UInt(Rm); if d == 15 || m == 15 then UNPREDICTABLE; 1 1 1 1 1 0 1 0 1 0 1 1 1 1 1 1 1 0 0 0 CLZ{<c>}{<q>} <Rd>, <Rm> d = UInt(Rd); m = UInt(Rm); n = UInt(Rn); if m != n || d == 15 || m == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13 m != n <c> See Standard assembler syntax fields. <q> See Standard assembler syntax fields. <Rd> Is the general-purpose destination register, encoded in the "Rd" field. <Rm> For encoding A1: is the general-purpose source register, encoded in the "Rm" field. <Rm> For encoding T1: is the general-purpose source register, encoded in the "Rm" field. It must be encoded with an identical value in the "Rn" field. if ConditionPassed() then EncodingSpecificOperations(); result = CountLeadingZeroBits(R[m]); R[d] = result<31:0>;