Instruction Syntax

Mnemonic	Format	Flags
blr		LK = 0
blrl		LK = 1

Note: BLR is a derived form of BCLR with BO=20 and BI=0, meaning it always branches (unconditional).

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	010011 (0x13)
BO	6-10	Branch Option (20 = always branch)
BI	11-15	Branch Input (0 = not used)
LK	31	Link (0 = no link, 1 = link)

Operation

if (LK == 0) then
    NIA ← LR
else
    NIA ← LR
    LR ← CIA + 4

Branch to the address contained in the Link Register (LR). If LK=1, the address of the instruction following the BLR is placed into LR.

Affected Registers

Link Register (LR)

(if LK = 1)

• Updated with the address of the instruction following BLR

Next Instruction Address (NIA)

• Set to the value in LR

Examples

Function Return

# Standard function return
blr              # Return to caller
blrl             # Return and set LR for next call

Subroutine Call and Return

# Call a subroutine
bl my_function   # Branch and link to function
# ... function code ...
blr              # Return to caller

Conditional Return

# Return only if condition is met
cmpwi r3, 0      # Compare r3 with 0
beq return       # Branch if equal
# ... continue processing ...
return:
blr              # Return to caller

Related Instructions

bclr, b, bc, bcctr, mflr, mtlr