bl

Branch with Link (A32)

BL<c> <label>

Calls a subroutine, storing return address in LR (R14).

Pseudocode Operation

if condition_satisfied then
  LR ← PC + 4
  PC ← PC + (sign_extend(imm24) << 2) + 8

Example

BL label

Encoding

Binary Layout

cond

31:28

101

27:25

imm24

23:0

Format Branch

Opcode 0x0B000000

Extension A32 (Base)

Operands

label
Label

Other forms of bl

bl Branch with Link

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x0B000000	BL{<c>}{<q>} <label>		A32		cond \| 101 \| 1 \| imm24
0xF000D000	BL{<c>}{<q>} <label>		T32		11110 \| S \| imm10 \| 11 \| J1 \| 1 \| J2 \| imm11

Description

Branch with Link calls a subroutine at a PC-relative address, and setting LR to the return address. Branch with Link and Exchange Instruction Sets (immediate) calls a subroutine at a PC-relative address, setting LR to the return address, and changes the instruction set from A32 to T32, or from T32 to A32.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    if CurrentInstrSet() == InstrSet_A32 then
        LR = PC - 4;
    else
        LR = PC<31:1> : '1';
    bits(32) targetAddress;
    if targetInstrSet == InstrSet_A32 then
        targetAddress = Align(PC,4) + imm32;
    else
        targetAddress = PC + imm32;
    SelectInstrSet(targetInstrSet);
    BranchWritePC(targetAddress, BranchType_DIRCALL);

bl