TBNZ
Test bit and branch if nonzero
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.
It provides a hint that this is not a subroutine call or return.
This instruction does not affect condition flags.
0
1
1
0
1
1
1
TBNZ <R><t>, #<imm>, <label>
constant integer t = UInt(Rt);
constant integer datasize = 32 << UInt(b5);
constant integer bit_pos = UInt(b5:b40);
constant bits(64) offset = SignExtend(imm14:'00', 64);
<R>
Is a width specifier,
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.
constant bits(datasize) operand = X[t, datasize];
constant boolean branch_conditional = TRUE;
if operand<bit_pos> != '0' then
BranchTo(PC64 + offset, BranchType_DIR, branch_conditional);
else
BranchNotTaken(BranchType_DIR, branch_conditional);