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Comment by matja | Hacker News Reader

addl is not necessary if it is not ambiguous

    add $4, %eax

- is fine

Compare with

    add 4, %eax

The "less noisy" Intel syntax becomes:

    add eax, DWORD PTR [4]

Most assemblers for Intel syntax will let you write:

    add eax, [4]

if you desire. Indeed, many disassemblers will follow suit in unambiguous cases. IDA, for example, does this.

The only time “DWORD PTR” is required is when (1) you're working with old assemblers, or (2) you're using a memory operand with an immediate:

    add eax, [4]       ; inferred
    add [eax], 4       ; ambiguous
    add DWORD [eax], 4 ; explicit

A disassembler may output it when not necessary, however.