vupkhpx

Vector Unpack High Pixel

vupkhpx vD, vB

Unpacks high 4 pixels to 4 words.

Details

Unpacks the four high-order pixel values (each 8 bits) from vB into four 32-bit word elements in vD, expanding each pixel into a word with implicit format expansion. This VMX/AltiVec instruction is commonly used in graphics processing and does not affect status registers.

Pseudocode Operation

for i in 0 to 3:
  pixel ← vB[8*(i+4):8*(i+4)+7]
  vD[32*i:32*i+31] ← ExpandPixel(pixel)

Programming Note

The vupkhpx instruction is used to unpack the high halfwords of a vector register into bytes, sign-extending the most significant bit and zero-extending the remaining bits. Ensure that the Vector Facility (MSR.VEC) is enabled before using this instruction; otherwise, a Vector_Unavailable exception will be raised. This operation is useful for processing pixel data where each pixel requires byte-level manipulation.

Example

vupkhpx vd, vb

Encoding

Binary Layout
4
0
vD
6
0
11
vB
16
846
21
 
Format VX-form
Opcode 0x1000034E
Extension VMX (AltiVec)
Registers Altered MSR

Operands

  • vD
    Target
  • vB
    Source