TBNZ

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

Decode

let t : integer = UInt(Rt); let datasize : integer{} = 32 << UInt(b5); let bit_pos : integer = UInt(b5::b40); let offset : bits(64) = SignExtend{}(imm14::'00');

Assembler Symbols

<R>

Is a width specifier, encoded in b5:

b5	<R>
0	W
1	X

In assembler source code an 'X' specifier is always permitted, but a 'W' specifier is only permitted when the bit number is less than 32.

<t>	Is the number [0-30] of the general-purpose register to be tested or the name ZR (31), encoded in the "Rt" field.

<imm>

Is the bit number to be tested, in the range 0 to 63, encoded in "b5:b40".

<label>

Is the program label to be conditionally branched to. Its offset from the address of this instruction, in the range +/-32KB, is encoded as "imm14" times 4.

Operation

let operand : bits(datasize) = X{}(t); let branch_conditional : boolean = TRUE; if operand[bit_pos] != '0' then BranchTo{64}(PC64() + offset, BranchType_DIR, branch_conditional); else BranchNotTaken(BranchType_DIR, branch_conditional); end;

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
b5	0	1	1	0	1	1	1	b40					imm14														Rt
							op

Encoding

Decode

Assembler Symbols

Operation