xxeval

VSX Vector Evaluation

xxeval XT, XA, XB, XC, IMM

Performs an arbitrary 3-input boolean logic function (LUT3) on vectors. The 8-bit immediate 'IMM' defines the truth table.

Encoding

Binary Layout

1

0:5

1

6:7

0

8

/

9:31

60

32:37

XT

38:42

XA

43:47

XB

48:52

XC

53:55

IMM

56:63

 

Format 8RR:XX4-form

Opcode 0x0500000088000010

Extension VSX

Operands

• XT
  Target
• XA
  Source A
• XB
  Source B
• XC
  Source C
• IMM
  Truth Table (8-bits)
• RT
  Target Vector Register
• RA
  Source Vector Register A
• RB
  Source Vector Register B
• RC
  Source Vector Register C

Example

xxeval 0, 1, 2, 3, 0x96

// Custom logic function (e.g., A^B^C).

Registers Altered

MSR

Related

More in VSX

Reference

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

Description

VSX instruction that performs a three-input lookup-table (LUT3) boolean operation on 128-bit vectors. The 8-bit immediate IMM encodes a truth table; for each bit position, the corresponding bit is determined by treating the three input bits (from XA, XB, XC) as a 3-bit selector into IMM. Requires VSX support; no condition flags are affected.

Operation

for i in 0..127 do
  selector ← (XC[i] || XB[i] || XA[i])
  XT[i] ← IMM[selector]
end for

Programming Note

The xxeval instruction is used to perform complex logical operations on vector registers.