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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.

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

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

integer d = UInt(Rd); integer n = UInt(Rn); if size != '00' then UNDEFINED; integer esize = 8; integer datasize = if Q == '1' then 128 else 64; 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:
sizeQ<T>
0008B
00116B
01xRESERVED
1xxRESERVED
<T>

Is an arrangement specifier, encoded in size:Q:

sizeQ<T>
0008B
00116B
01xRESERVED
1xxRESERVED
<Vn>

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

Operation

CheckFPAdvSIMDEnabled64(); bits(datasize) operand = V[n]; 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] = result;

Operational information

If PSTATE.DIT is 1:


Internal version only: isa v32.13v32.12, AdvSIMD v29.05v29.04, pseudocode v2020-12v2020-09_xml, sve v2020-12v2020-09_rc3 ; Build timestamp: 2020-12-16T142020-11-18T17:1723

Copyright © 2010-2020 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.

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