CBZ

Compare and Branch on Zero compares the value in a register with zero, and conditionally branches to a label at a PC-relative offset if the comparison is equal. It provides a hint that this is not a subroutine call or return. This instruction does not affect condition flags.

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
sf	0	1	1	0	1	0	0	imm19																			Rt
							op

32-bit (sf == 0)

CBZ <Wt>, <label>

64-bit (sf == 1)

CBZ <Xt>, <label>

integer t = UInt(Rt);
constant integer datasize = 32 << UInt(sf);
bits(64) offset = SignExtend(imm19:'00', 64);

Assembler Symbols

<Wt>	Is the 32-bit name of the general-purpose register to be tested, encoded in the "Rt" field.

<Xt>	Is the 64-bit name of the general-purpose register to be tested, encoded in the "Rt" field.

<label>

Is the program label to be conditionally branched to. Its offset from the address of this instruction, in the range +/-1MB, is encoded as "imm19" times 4.

Operation

bits(datasize) operand1 = X[t, datasize];
if IsZero(operand1) == TRUE then
    BranchTo(PC64 + offset, BranchType_DIR, TRUE);
else
    BranchNotTaken(BranchType_DIR, TRUE);