prtyd

Parity Doubleword

prtyd RA, RS

Calculates parity of a doubleword (Scalar).

Encoding

Binary Layout

31

0:5

RS

6:10

RA

11:15

/

16:20

186

21:30

/

31

 

Format X-form

Opcode 0x7C000174

Extension Base

Operands

• RA
  Target
• RS
  Source
• RT
  Target General Purpose Register
• RB
  Source General Purpose Register

Example

prtyd r4, r3

Registers Altered

CR0, XER

Related

More in Base

Reference

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

Description

Computes the parity of the entire 64-bit doubleword in register RS by XORing all 64 bits and stores the result (a single bit) in the low bit of register RA. All other bits of RA are cleared to zero. No condition registers or status fields are affected.

Operation

parity_bit ← 0
for i in 0 to 63 do
  parity_bit ← parity_bit XOR RS[i]
end
RA ← (0b0000000000000000000000000000000000000000000000000000000000000 || parity_bit)

Programming Note

The prtyd instruction is useful for parity checking on doubleword values. It sets the least significant bit of RA based on the parity of each byte in RS, which can be helpful for error detection. Ensure that RS and RA are properly aligned to avoid unexpected behavior. This instruction operates at user privilege level.