vclzlsbb

Vector Count Leading Zero Least Significant Bits Byte

vclzlsbb RA, vB

Counts the number of contiguous leading byte elements in VSR[VRB+32] having a zero least-significant bit.

Details

The instruction counts the number of contiguous leading byte elements in VSR[VRB+32] that have a zero least-significant bit and places the count into GPR[RT].

Pseudocode Operation

if MSR.VEC=0 then
    Vector_Unavailable()
count ←0
do while count < 16
    if VSR[VRB+32].byte[count].bit[7]=1 then
        break
    count ←count + 1
end
GPR[RT] ←EXTZ64(count)

Programming Note

This instruction is useful for counting leading zero least significant bits in a vector register. Ensure that the Vector Facility (MSR.VEC) is enabled; otherwise, a Vector_Unavailable exception will be raised. The operation processes 16 bytes, and the result is stored in a general-purpose register. Be cautious of alignment requirements when accessing vector registers.

Example

vclzlsbb r4, vb

Encoding

Binary Layout
4
0
RT
6
0
11
VRB
16
1538
21
 
Format VX-form
Opcode 0x10000602
Extension VMX (AltiVec)
Registers Altered MSR

Operands

  • RA
    Target GPR
  • vB
    Source
  • RT
    Target General Purpose Register
  • VRB
    Source Vector Register
  • VRT
    Target Vector Register
  • VSRC
    Source Vector Register