tbnz

Test Bit Not Zero

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

Branches if specified bit is 1.

Pseudocode Operation

bit_index ← (b5 << 5) | imm14; if (Wt|Xt)[bit_index] == 1 then PC ← label

Example

TBNZ Wt, #16, label

Encoding

Binary Layout

b5

31

011011

30:25

1

24

b40

23:19

imm14

18:5

Rt

4:0

 

Format Branch

Opcode 0x37000000

Extension Base

Operands

• Wt
  Reg
• imm
  Bit
• label
  Label

Related

More in Base

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x37000000	TBNZ <R><t>, #<imm>, <label>		A64		b5 | 011011 | 1 | b40 | imm14 | Rt

Description

Test bit and Branch if Nonzero 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. 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);