From a high-level academic view, yes, the compiler is allowed to perform any legal transformation. But in practice C compilers are pretty conservative about what they emit, especially when code is compiled without -march= .

You don't have to take my word for it. Go find a moderately complex open-source library written in C, compile it, then open up the result in Hexrays/Ghidra/radare2/whatever. Compare the compiled functions with their original source and you'll see there's not that much magic going on.