xvi8ger4spp

VSX Vector 8-bit Signed/Unsigned Integer GER (rank-4 update) with Saturation Positive multiply, Positive accumulate

xvi8ger4spp AT,XA,XB

Performs a vector-scalar operation on 8-bit signed and unsigned integers with saturation.

Encoding

Binary Layout

0:5

6:10

11:15

16:20

21:25

26:28

Format XX3-form

Opcode 0xEC000318

Extension VSX

Operands

AT
Target Vector Register
XA
Source Vector Register
XB
Source Vector Register

Example

xvi8ger4spp acc0, vs2, vs3

Registers Altered

VSCR, ACC

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Performs a 4×4 generalized outer product (GER) on 8-bit signed/unsigned integers from XA and XB, accumulating the products into the 32-bit accumulator AT with saturation applied. Results with positive products and positive accumulation ('pp' suffix) are saturated to the signed 32-bit range. This is a VSX instruction requiring the MMA category support.

Operation

acc ← AT
for i in 0 to 3 do
  for j in 0 to 3 do
    a ← sign_extend(XA[i*8:(i+1)*8-1], 8)
    b ← sign_extend(XB[j*8:(j+1)*8-1], 8)
    prod ← a × b
    acc[i*32+j*8:(i*32+j*8+31)] ← SATURATE_S32(acc[i*32+j*8:(i*32+j*8+31)] + prod)
  end for
end for
AT ← acc

Programming Note

This instruction is used for performing vector-scalar operations on 8-bit signed and unsigned integers, multiplying corresponding elements of two vectors and accumulating the results into an accumulator with saturation handling. Ensure that the VSX (Vector Scalar Extensions) are enabled in the MSR register to avoid a 'VSX_Unavailable' exception. The operation involves multiple steps of multiplication and accumulation, which can be computationally intensive; consider optimizing vector sizes and operations for performance.