Addressing the adding situation

In the quirky world of x86 architecture, adding two integers isn’t as straightforward as you’d expect—thanks to its finicky two-operand limit that forces instructions like ADD to overwrite the first operand, leaving you without a separate destination register like on more flexible ARM chips. Enter the LEA (Load Effective Address) instruction, which compilers cleverly hijack as a makeshift calculator to perform these additions without actually touching memory, letting you add multiple registers and specify where the result lands, all while preserving your original values. This neat trick turns x86’s complex addressing modes—complete with offsets, scales, and shifts—into a powerhouse for efficient computations, often shaving off instructions and boosting performance on multi-execution units. For tech-savvy SMBs and MSPs managing custom software or embedded systems, understanding this compiler magic means you can optimize code for better speed and resource use, especially in performance-critical apps, without diving too deep into assembly yourself. And hey, if you’re following Matt Godbolt’s Advent of Compiler Optimisations series, it’s a reminder that even old-school hardware has hidden gems worth exploiting.

Source: https://xania.org/202512/02-adding-integers