GCC Return optimiztion

Question

I\'d like to know if GCC can optimize code like

int foo(args) {
    if(is_true) {
        do_smth;
        n = call_func(args);
        do_smth;
        retu         


        

Answer 1

This is called tail-call optimization (it is not specified in any C standard; in contrast, some languages -e.g. Scheme and Ocaml- specify that tail-call optimization is required to happen). In some cases, recent GCC compilers can do that optimization.

But it really depends upon the details, in particular of the actual arguments passed to call_func

If you depend on it, please comment your code and check with gcc -fverbose-asm -O2 -S that your compiler is doing that.

Notice that this optimization is not required, and might be compiler, compilation flags, processor and ABI specific.

^{(so it could work on x86-64 but not on 32 bits ia32 or ARM; you really should check!)}