vpopcntw

Vector Population Count Word

vpopcntw vD, vB

Counts the number of bits set to 1 in each word element of a vector register.

Details

For vpopcntw, the number of bits set to 1 in each word element of VSR[VRB+32] is counted and placed into the corresponding word element of VSR[VRT+32].

Pseudocode Operation

if MSR.VEC=0 then
    Vector_Unavailable()
do i = 0 to 3
    n ←0
    do j = 0 to 31
        n ←n + VSR[VRB+32].word[i].bit[j]
    end
    VSR[VRT+32].word[i] ←n
end

Programming Note

This instruction counts the number of set bits (1s) in each 32-bit word of the source vector and stores the result in the destination vector. Ensure that the Vector Facility is enabled by checking and setting the VEC bit in the MSR register. This instruction operates on 128-bit vectors, processing four 32-bit words per operation.

Example

vpopcntw vd, vb

Encoding

Binary Layout
4
0
vD
6
0
11
vB
31
1923
 
Format VX-form
Opcode 0x10000783
Extension VMX (AltiVec)
Registers Altered MSR

Operands

  • vD
    Target
  • vB
    Source
  • VRT
    Target Vector Register
  • VRB
    Source Vector Register