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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.


14-bit signed PC-relative branch offset

TBNZ <R><t>, #<imm>, <label>

integer t = UInt(Rt);

integer datasize = if b5 == '1' then 64 else 32;
integer bit_pos = UInt(b5:b40);
bits(64) offset = SignExtend(imm14:'00', 64);

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.

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


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


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.


bits(datasize) operand = X[t];

if operand<bit_pos> == op then
    BranchTo(PC[] + offset, BranchType_DIR);
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