X86-assembly/Instructions/shl

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X86-assembly

Instructions

shl/sal

Description

• The shl or sal instruction is used to shift the bits of the operand destination to the left, by the number of bits specified in the count operand.
• Bits shifted beyond the destination are first shifted into the CF flag.
• Zeros fill vacated positions during the shift operation.
• Equivalent to multiplying by 2ⁿ

This is the equivalent to this function in python:

>>> def shl(dest, count):
...   return hex(dest << count)
... 
>>> shl(0xA, 2)
'0x28'

Syntax

shl destination, count

Example

mov eax, 0xA  ; set EAX to 0xA (1010 in binary)
shl eax, 2    ; shifts 2 bits left in EAX, now equal to 0x28 (101000 in binary)

shl eax, 1   ;Equivalent to EAX*(2^1) or EAX*2
shl eax, 2   ;Equivalent to EAX*(2^2) or EAX*4
shl eax, 3   ;Equivalent to EAX*(2^3) or EAX*8
shl eax, 4   ;Equivalent to EAX*(2^4) or EAX*16
shl eax, 5   ;Equivlaent to EAX*(2^5) or EAX*32
shl eax, 6   ;Equivalent to EAX*(2^6) or EAX*64
shl eax, 7   ;Equivalent to EAX*(2^7) or EAX*128
shl eax, 8   ;Equivalent to EAX*(2^8) or EAX*256