C++: Structs slower to access than basic variables?

Question

I found some code that had \"optimization\" like this:

void somefunc(SomeStruct param){
    float x = param.x; // param.x and x are both floats. supposedly this          


        

Answer 1

In an unoptimised code:

• function parameters (which are not passed by reference) are on the stack
• local variables are also on the stack

Unoptimised access to local variables and function parameters in an assembly language look more-or-less like this:

mov %eax, %ebp+ compile-time-constant

where %ebp is a frame pointer (sort of 'this' pointer for a function).

It makes no difference if you access a parameter or a local variable.

The fact that you are accessing an element from a struct makes absolutely no difference from the assembly/machine point of view. Structs are constructs made in C to make programmer's life easier.

So, ulitmately, my answer is: No, there is absolutely no benefit in doing that.