Page 87 - ARM 64 Bit Assembly Language

72 Chapter 3

11 mov w0, #1
12 endif1:
13
14 // return w0
15 ldp x29, x30, [sp], #16
16 ret

3.5.2 Branch register

These instructions allow the program counter to be set to the value contained in a 64-bit
general-purpose register (x0-x30):

br Branch to Register and
ret Return from Subroutine.

3.5.2.1 Syntax

br Xn
ret {Xn}

• ret uses the procedure link register (LR), which is x30, if no register is specified.
• ret is only used to return from a subroutine.
• br can be used for implementing a computed goto (switch statement).

3.5.2.2 Operations

Name Effect Description
br pc ← Xn Copy register Xn to the program
counter (pc).
ret pc ← X30 or pc ← Xn Copy the link register (X30), or any
other register (Xn) to the program
counter (pc).

3.5.2.3 Examples

The branch register instruction will set the pc register to the contents of a register:

1 br x10
This can generate a Segmentation Fault if the contents of x10 are invalid. If not, the processor
will begin executing instructions at the address contained in x10.