Volume 3: General-Purpose and System Instructions - Stanford ...

AMD64 Technology 24594 Rev. 3.10 February 2005SBBSubtract with BorrowSubtracts an immediate value or the value in a register or a memory location (secondoperand) from a register or a memory location (first operand), and stores the result inthe first operand location. If the carry flag (CF) is 1, the instruction subtracts 1 fromthe result. Otherwise, it operates like SUB.The SBB instruction sign-extends immediate value operands to the length of the firstoperand size.This instruction evaluates the result for both signed and unsigned data types and setsthe OF and CF flags to indicate a borrow in a signed or unsigned result, respectively. Itsets the SF flag to indicate the sign of a signed result.This instruction is useful for multibyte (multiword) numbers because it takes intoaccount the borrow from a previous SUB instruction.The forms of the SBB instruction that write to memory support the LOCK prefix. Fordetails about the LOCK prefix, see “Lock Prefix” on page 10.Mnemonic Opcode DescriptionSBB AL, imm8SBB AX, imm16SBB EAX, imm32SBB RAX, imm32SBB reg/mem8, imm8SBB reg/mem16, imm16SBB reg/mem32, imm32SBB reg/mem64, imm321C ib1D iw1D id1D id80 /3 ib81 /3 iw81 /3 id81 /3 idSubtract an immediate 8-bit value from the AL register withborrow.Subtract an immediate 16-bit value from the AX register withborrow.Subtract an immediate 32-bit value from the EAX register withborrow.Subtract a sign-extended immediate 32-bit value from the RAXregister with borrow.Subtract an immediate 8-bit value from an 8-bit register ormemory location with borrow.Subtract an immediate 16-bit value from a 16-bit register ormemory location with borrow.Subtract an immediate 32-bit value from a 32-bit register ormemory location with borrow.Subtract a sign-extended immediate 32-bit value from a 64-bitregister or memory location with borrow.262 SBB