The compiler knows how it's aligning variables, It's a pure performance issue: location of things in memory affects alignment to caching unit boundaries (access

The compiler knows how it's aligning variables, It's a pure performance issue: location of things in memory affects alignment to caching unit boundaries (accessing one more cache line for the same data) and cache pressure (data ends up cached in the same location as something else, causing unnecessary evictions while other cache locations remains underused)