CLZ

Count leading zeros

This instruction 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.

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

32-bit encoding

(sf == 0)

CLZ <Wd>, <Wn>

64-bit encoding

(sf == 1)

CLZ <Xd>, <Xn>

Decode (all encodings)

constant integer d = UInt(Rd); constant 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

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

Operational information

This instruction is a data-independent-time instruction as described in About PSTATE.DIT.

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