stdx

Store Doubleword Indexed X-form

stdx RS,RA,RB

Stores a doubleword from a register to memory using an indexed address.

Encoding

Binary Layout

62

0:5

RS

6:10

RA

11:15

RB

16:31

 

Format X-form

Opcode 0x7C00012A

Extension Base

Operands

• RS
  Source General Purpose Register
• RA
  Base Address General Purpose Register
• RB
  Index General Purpose Register

Example

stdx r3, r4, r5

Related

More in Base

Reference

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

Description

Stores a doubleword (64 bits) from register RS to memory at the address formed by adding the contents of RA and RB. The effective address is calculated as (RA|0) + RB. No condition registers or status fields are modified by this instruction.

Operation

EA ← (RA|0) + RB
[EA] ← RS[0:63]

Programming Note

The stdx instruction is commonly used for storing a doubleword from a register into memory at an address derived from the sum of two registers. Ensure that RA and RB are correctly set to avoid incorrect memory addresses. This instruction operates in user mode and can raise exceptions if there's a protection fault or alignment error.