pmxvbf16ger2

Prefixed Masked VSX Vector BFloat16 Ger (Rank-2 Update)

pmxvbf16ger2 AT, XA, XB, XMSK, YMSK

Matrix Multiply Assist (MMA) instruction. Computes ACC <- ACC + (A * B) using BF16 inputs.

Encoding

Binary Layout

1

0

3

6

PMSK

8

XMSK

9

YMSK

14

0

32

59

38

AT

41

/

43

XA

48

XB

53

XO

56

AX

57

BX

58

/

 

Format MMIRR-form

Opcode 0x07900000EC000198

Extension Prefixed

Operands

• AT
  Accumulator (0-7)
• XA
  Vector A
• XB
  Vector B
• XMSK
  Mask for A
• YMSK
  Mask for B

Example

pmxvbf16ger2 0, 1, 2, 0, 0

// AI Tensor Core operation.

Related

More in Prefixed

Reference

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

Description

Prefixed MMA instruction that performs a masked rank-2 generalized matrix multiply using BFloat16 inputs. Computes ACC(AT) ← ACC(AT) + (A × B) with element-wise masking via XMSK (for rows of A) and YMSK (for columns of B). Requires MMA support and VSX category. Updates CR6 to reflect accumulator saturation status.

Operation

acc ← ACC[AT]
for i in 0..1 do
  for j in 0..3 do
    if XMSK[i] = 1 ∧ YMSK[j] = 1 then
      acc[i,j] ← acc[i,j] + (BF16(XA[i]) × BF16(XB[j]))
ACC[AT] ← acc
CR6 ← saturation_status(acc)

Programming Note

The pmxvbf16ger2 instruction is useful for performing matrix operations on bfloat16 data types with masking, allowing selective computation based on a mask. Ensure that the input vectors and accumulator are properly aligned to avoid performance penalties. This instruction operates at the user privilege level and will raise an exception if the result exceeds the 32-bit signed integer range, requiring saturation handling.