SHL Shift Left

Flags affected:

        O D I T S Z A P C  OF: Overflow flag  TF: Trap flag AF: Aux carry
        F F F F F F F F F  DF: Direction flag SF: Sign flag PF: Parity flag
        *       * * * * *  IF: Interrupt flag ZF: Zero flag CF: Carry flag

Legal forms:

        SHL r8,1
        SHL m8,1
        SHL r16,1
        SHL m16,1
        SHL r32,1    386+
        SHL m32,1    386+
        SHL r8,CL
        SHL m8,CL
        SHL r16,CL
        SHL m16,CL
        SHL r32,CL   386+
        SHL m32,CL   386+
        SHL r8,i8    286+
        SHL m8,i8    286+
        SHL r16,i8   286+
        SHL m16,i8   286+
        SHL r32,i8   386+
        SHL m32,i8   386+

Examples:

        SHL AL,1
        SHL WORD [BX+SI],CL
        SHL BP,1
        SHL EAX,9
        SHL BP,CL

Notes:

SHL shifts the bits within the destination operand to the left, where left is toward the most significant bit (MSB). The number of bit positions shifted may be specified either as an 8-bit immediate value, or by the value in CL-not CX or ECX. (The 8086 and 8088 are limited to the immediate value 1.) Note that while CL may accept a value up to 255, it is meaningless to shift by any value larger than 16-or 32 in 32-bit mode-even though the shifts are actually performed on the 8086 and 8088. (The 286 and later limit the number of shift operations performed to the native word size except when running in Virtual 86 mode.) The leftmost bit of the operand is shifted into the Carry flag; the rightmost bit is cleared to 0. The Auxiliary carry flag (AF) becomes undefined after this instruction. OF is modified only by the shift-by-one forms of SHL; after shift-by-CL forms, OF becomes undefined.

SHL is a synonym for SAL (Shift Arithmetic Left). Except for the direction the shift operation takes, SHL is identical to SHR.

        r8 = AL AH BL BH CL CH DL DH        r16 = AX BX CX DX BP SP SI DI
        sr = CS DS SS ES FS GS              r32 = EAX EBX ECX EDX EBP ESP ESI EDI
        m8 = 8-bit memory data              m16 = 16-bit memory data
        m32 = 32-bit memory data            i8 = 8-bit immediate data
        i16 = 16-bit immediate data         i32 = 32-bit immediate data
        d8 = 8-bit signed displacement      d16 = 16-bit signed displacement
        d32 = 32-bit unsigned displacement