vmaxub

Vector Maximum Unsigned Byte

vmaxub vD, vA, vB

Selects maximum value per byte (unsigned).

Details

The vmaxub instruction compares each byte element of two vector registers and stores the larger unsigned byte value in the corresponding element of a third vector register.

Pseudocode Operation

if MSR.VEC=0 then Vector_Unavailable()
do i = 0 to 15
   src1 ←VSR[VRA+32].byte[i]
   src2 ←VSR[VRB+32].byte[i]

   gt_flag ←EXTZ(src1) > EXTZ(src2)
   VSR[VRT+32].byte[i] ←gt_flag=1 ? src1 : src2
end

Programming Note

The vmaxub instruction is used to perform element-wise comparison of unsigned bytes from two vector registers and store the maximum values in a third register. Ensure that the Vector Facility (MSR.VEC) is enabled before using this instruction; otherwise, it will raise an exception. This instruction operates on 16-byte vectors, so ensure proper alignment for optimal performance.

Example

vmaxub vd, va, vb

Encoding

Binary Layout

Format VA-form

Opcode 0x10000004

Extension VMX (AltiVec)

Registers Altered MSR

Operands

vD
Target
vA
Src A
vB
Src B