Index

CTZ

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

Integer
(FEAT_CSSC)

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

32-bit (sf == 0)

CTZ <Wd>, <Wn>

64-bit (sf == 1)

CTZ <Xd>, <Xn>

if !IsFeatureImplemented(FEAT_CSSC) then UNDEFINED;
constant integer datasize = 32 << UInt(sf);
integer n = UInt(Rn);
integer d = UInt(Rd);

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(BitReverse(operand1));
X[d, datasize] = result<datasize-1:0>;

Operational information

If PSTATE.DIT is 1: