tbz

Test Bit Zero

TBZ <Wt|Xt>, #<imm>, <label>

Branches if specified bit is 0.

Pseudocode Operation

bit_index ← (b5 << 5) | imm14; if (Wt|Xt)[bit_index] == 0 then PC ← label

Example

TBZ Wt, #16, label

Encoding

Binary Layout

011011

30:25

b40

23:19

imm14

18:5

4:0

Format Branch

Opcode 0x36000000

Extension Base

Operands

Wt
Reg
imm
Bit
label
Label

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x36000000	TBZ <R><t>, #<imm>, <label>		A64		b5 \| 011011 \| 0 \| b40 \| imm14 \| Rt

Description

Test bit and Branch if Zero compares the value of a test bit 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.

Operation

bits(datasize) operand = X[t, datasize];
if operand<bit_pos> == op then
    BranchTo(PC64 + offset, BranchType_DIR, TRUE);
else
    BranchNotTaken(BranchType_DIR, TRUE);

tbz