BL

Branch with link

This instruction branches to a PC-relative offset, setting register X30 to PC+4. It provides a hint that this is a subroutine call.

Encoding: 26-bit signed PC-relative branch offset

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	0	0	1	0	1
op						imm26

BL <label>

Decoding algorithm

constant bits(64) offset = SignExtend(imm26:'00', 64);
constant integer d = 30;

Operation

if IsFeatureImplemented(FEAT_GCS) && GCSPCREnabled(PSTATE.EL) then
    AddGCSRecord(PC64 + 4);
X[d, 64] = PC64 + 4;

constant boolean branch_conditional = FALSE;
BranchTo(PC64 + offset, BranchType_DIRCALL, branch_conditional);

Explanations

<label>: Is the program label to be unconditionally branched to. Its offset from the address of this instruction, in the range +/-128MB, is encoded as "imm26" times 4.