TBNZ

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.

313029282726252423222120191817161514131211109876543210
b50110111b40imm14Rt
op

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

integer t = UInt(Rt); constant integer datasize = 32 << UInt(b5); integer bit_pos = UInt(b5:b40); bit iszero = op; 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.
<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

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


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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