Compare registers and branch
This instruction compares the values in two registers, and conditionally branches to a label at a PC-relative offset if the condition is true. This instruction provides a hint that this is not a subroutine call or return. This instruction does not affect the condition flags.
This instruction is used by the pseudo-instructions CBLE (register), CBLO (register), CBLS (register), and CBLT (register).
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| sf | 1 | 1 | 1 | 0 | 1 | 0 | 0 | cc | Rm | 0 | 0 | imm9 | Rt | ||||||||||||||||||
if !IsFeatureImplemented(FEAT_CMPBR) then EndOfDecode(Decode_UNDEF); end; let datasize : integer{} = 32 << UInt(sf); let t : integer = UInt(Rt); let m : integer = UInt(Rm); let offset : bits(64) = SignExtend{}(imm9::'00'); var op : CmpOp; var unsigned : boolean; case cc of when '000' => op = Cmp_GT; unsigned = FALSE; when '001' => op = Cmp_GE; unsigned = FALSE; when '010' => op = Cmp_GT; unsigned = TRUE; when '011' => op = Cmp_GE; unsigned = TRUE; when '110' => op = Cmp_EQ; unsigned = TRUE; when '111' => op = Cmp_NE; unsigned = TRUE; otherwise => EndOfDecode(Decode_UNDEF); end;
| <Wt> |
Is the 32-bit name of the general-purpose register to be tested, encoded in the "Rt" field. |
| <Wm> |
Is the 32-bit name of the second general-purpose source register, encoded in the "Rm" field. |
| <label> |
Is the program label to be conditionally branched to. Its offset from the address of this instruction, in the range -1024 to 1020, is encoded as "imm9" times 4. |
| <Xt> |
Is the 64-bit name of the general-purpose register to be tested, encoded in the "Rt" field. |
| <Xm> |
Is the 64-bit name of the second general-purpose source register, encoded in the "Rm" field. |
let operand1 : bits(datasize) = X{}(t); let operand2 : bits(datasize) = X{}(m); let branch_conditional : boolean = TRUE; let value1 : integer = if unsigned then UInt(operand1) else SInt(operand1); let value2 : integer = if unsigned then UInt(operand2) else SInt(operand2); var cond : boolean; case op of when Cmp_EQ => cond = value1 == value2; when Cmp_NE => cond = value1 != value2; when Cmp_GE => cond = value1 >= value2; when Cmp_GT => cond = value1 > value2; end; if cond then BranchTo{64}(PC64() + offset, BranchType_DIR, branch_conditional); else BranchNotTaken(BranchType_DIR, branch_conditional); end;
2026-03_rel 2026-03-26 20:48:11
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