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CBZ

Compare and Branch on Zero compares the value in a register 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.

313029282726252423222120191817161514131211109876543210
sf0110100imm19Rt
op

32-bit (sf == 0)

CBZ <Wt>, <label>

64-bit (sf == 1)

CBZ <Xt>, <label>

integer t = UInt(Rt);
integer datasize = if sf == '1' then 64 else 32;
bits(64) offset = SignExtend(imm19:'00', 64);

Assembler Symbols

<Wt>

Is the 32-bit name of the general-purpose register to be tested, encoded in the "Rt" field.

<Xt>

Is the 64-bit name of the general-purpose register to be tested, encoded in the "Rt" field.

<label>

Is the program label to be conditionally branched to. Its offset from the address of this instruction, in the range +/-1MB, is encoded as "imm19" times 4.

Operation

bits(datasize) operand1 = X[t];

if IsZero(operand1) == TRUE then
    BranchTo(PC[] + offset, BranchType_DIR);
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