Understanding Integer Addition in x86 Assembly: Why It's More Complex Than Expected
By
messe
Crisp on the outside, thoughtful on the inside. A keeper.
Summary
The article explores the seemingly simple task of adding two integers in x86 assembly language, revealing that it's more complex than expected due to x86's two-operand instruction architecture. The author compares x86 to ARM architecture, where adding is more straightforward with three-operand instructions. The piece explains why x86 requires different approaches for integer addition and discusses compiler optimization strategies for this basic operation.
Key quotes
· 5 pulledx86 is unusual in mostly having a maximum of two operands per instruction
There's no add instruction to add edi to esi, putting the result in eax
On an ARM machine this would be a simple add r0, r0, r1 or similar
What do you think a simple x86 function to add two ints would look like? An add, right? Let's take a look!
Probably not what you were thinking, right?
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