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jalr

Jump and link register

Saves the return address in $t1 and jumps to the address in $t2; with one register, the return address goes to $ra.

Forms

  • jalr ,
  • jalr

    Saves the return address (PC + 4) in $ra, then jumps to the address in $t1. One-operand shorthand for 'jalr $ra,$t1'. Used to call a function via a pointer stored in a register.

Operands

$t1
Any general-purpose register, $0 to $31, using its numeric or named spelling, such as $8 or $t0 ($zero is $0; $ra is $31).
$t2
A general-purpose register. It may be the same register as $t1.

Allows calling a function whose address is only known at runtime (function pointer). Return with 'jr $t1'.

# jalr calls a local routine and writes the return address to $ra. Inspect $t2: 1 after return.
la $t0, routine
jalr $t0
li $t2, 1
b done # Skip the routine after returning.
routine: li $t2, 2
jr $ra # Return to the instruction after the call.
done: