1C ib         SBB AL, imm8         Subtract with borrow imm8 from AL

1D iw         SBB AX, imm16         Subtract with borrow imm16 from AX

1D id         SBB EAX, imm32         Subtract with borrow imm32 from EAX

80 /3 ib         SBB r/m8,imm8         Subtract with borrow imm8 from r/m8

81 /3 iw         SBB r/m16,imm16         Subtract with borrow imm16 from r/m16

81 /3 id         SBB r/m32,imm32         Subtract with borrow imm32 from r/m32

83 /3 ib         SBB r/m16,imm8         Subtract with borrow sign-extended imm8 from r/m16

83 /3 ib         SBB r/m32,imm8         Subtract with borrow sign-extended imm8 from r/m32

18 / r         SBB r/m8,r8         Subtract with borrow r8 from r/m8

19 / r         SBB r/m16,r16         Subtract with borrow r16 from r/m16

19 / r         SBB r/m32,r32         Subtract with borrow r32 from r/m32

1A / r         SBB r8,r/m8         Subtract with borrow r/m8 from r8

1B / r         SBB r16,r/m16         Subtract with borrow r/m16 from r16

1B / r         SBB r32,r/m32         Subtract with borrow r/m32 from r32


Description

Adds the source operand (second operand) and the carry (CF) flag, and subtracts the result from the destination operand (first operand). The result of the subtraction is stored in the destination operand. The destination operand can be a register or a memory location; the source operand can be an immediate, a register, or a memory location. (However, two memory operands cannot be used in one instruction.) The state of the CF flag represents a borrow from a previous subtraction.


When an immediate value is used as an operand, it is sign-extended to the length of the destination operand format.


The SBB instruction does not distinguish between signed or unsigned operands. Instead, the processor evaluates the result for both data types and sets the OF and CF flags to indicate a borrow in the signed or unsigned result, respectively. The SF flag indicates the sign of the signed result.


The SBB instruction is usually executed as part of a multibyte or multiword subtraction in which a SUB instruction is followed by a SBB instruction.


Operands        Bytes                Clocks

reg, reg             2                    1   PU

mem, reg          2+d(0,2)         3   PU

reg, mem          2+d(0,2)         2   PU

reg, imm          2+i(1,2)         1   PU

mem, imm          2+d(0,2)+i(1,2)         3   PU*

acc, imm          1+i(1,2)         1   PU


* = not pairable if there is a displacement and immediate


Flags

The OF, SF, ZF, AF, PF, and CF flags are set according to the result.

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