CNT

Population Count per byte. This instruction counts the number of bits that have a value of one in each vector element in the source SIMD&FP register, places the result into a vector, and writes the vector to the destination SIMD&FP register.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

313029282726252423222120191817161514131211109876543210
0Q001110size100000010110RnRd
Uopcode

CNT <Vd>.<T>, <Vn>.<T>

integer d = UInt(Rd); integer n = UInt(Rn); if size != '00' then UNDEFINED; constant integer esize = 8; constant integer datasize = 64 << UInt(Q); integer elements = datasize DIV 8;

Assembler Symbols

<Vd>

Is the name of the SIMD&FP destination register, encoded in the "Rd" field.

<T>

Is an arrangement specifier, encoded in size:Q:

size Q <T>
00 0 8B
00 1 16B
01 x RESERVED
1x x RESERVED
<Vn>

Is the name of the SIMD&FP source register, encoded in the "Rn" field.

Operation

CheckFPAdvSIMDEnabled64(); bits(datasize) operand = V[n, datasize]; bits(datasize) result; integer count; for e = 0 to elements-1 count = BitCount(Elem[operand, e, esize]); Elem[result, e, esize] = count<esize-1:0>; V[d, datasize] = result;

Operational information

If PSTATE.DIT is 1:


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

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