vcmpgtub

Vector Compare Greater Than Unsigned Byte

vcmpgtub vD, vA, vB

Unsigned > comparison for 16 bytes.

Details

The vcmpgtub instruction compares each byte of two source vectors as unsigned integers. If a byte in the first source vector is greater than the corresponding byte in the second source vector, the corresponding byte in the result vector is set to all 1s (0xFF). Otherwise, it is set to all 0s (0x00). The instruction also updates CR field 6 if Rc=1 to indicate whether all elements compared true and whether all elements compared false.

Pseudocode Operation

if MSR.VEC=0 then Vector_Unavailable()
all_true ←1
all_false ←1
do i = 0 to 15
   src1 ←EXTZ(VSR[VRA+32].byte[i])
   src2 ←EXTZ(VSR[VRB+32].byte[i])
   if src1 > src2 then do
      VSR[VRT+32].byte[i] ←0xFF
      all_false ←0
   end
   else do
      VSR[VRT+32].byte[i] ←0x00
      all_true ←0
   end
end
if Rc=1 then
   CR.field[6] ←all_true || 0b0 || all_false || 0b0

Programming Note

vcmpgtub is useful for comparing unsigned byte values in vectors. Ensure both source vectors are properly aligned to avoid alignment faults. The instruction updates CR field 6 if Rc=1, indicating comparison results; check this for conditional logic. Performance may vary based on vector length and data distribution.

Example

vcmpgtub vd, va, vb

Encoding

Binary Layout

518

Format VC-form

Opcode 0x10000206

Extension VMX (AltiVec)

Registers Altered MSR, CR6

Operands

vD
Target
vA
Src A
vB
Src B