addmeo

Add to Minus One Extended (Overflow)

addmeo RT,RA

Adds the contents of a register and a constant minus one, with optional overflow exception.

Encoding

Binary Layout

31

0:5

RT

6:10

RA

11:15

00000

16:20

OE

21

234

22:30

Rc

31

 

Format XO-form

Opcode 0x7C0001D4

Extension Base

Operands

• RT
  Target Register
• RA
  Source Register

Example

addme r3, r4

// r3 = r4 + CA - 1

Registers Altered

CR0, XER

Related

More in Base

Reference

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

Description

The sum (RA) + CA - 1 is placed into register RT. The carry bit (CA) is used in the calculation.

Operation

if 'addme' then
    RT <- (RA) + CA - 1

Extended Mnemonics

Extended Mnemonic	Equivalent Instruction

Programming Note

When Rc=1 (dot form), CR0 is updated with the signed comparison of the result against zero (LT, GT, EQ) and the current SO bit from XER.