CLZ -- A64

Count Leading Zeros counts the number of consecutive binary zero bits, starting from the most significant bit in the source register, and places the count in the destination register.

integer d = UInt(Rd); integer n = UInt(Rn); constant integer datasize = 32 << UInt(sf);

Assembler Symbols

<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.

Operation

bits(datasize) operand1 = X[n, datasize]; integer result = CountLeadingZeroBits(operand1); X[d, datasize] = result<datasize-1:0>;

Operational information

If PSTATE.DIT is 1:

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.

Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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	0	0	Rn					Rd
		S									opcode2										op

CLZ

32-bit (sf == 0)

64-bit (sf == 1)

Assembler Symbols

Operation

Operational information