I'm puzzled.
The fundamental rule of optimization is that it doesn't change the (defined)
semantics of the program. How is it possible to write valid C that is correct
only if some optimization is done?
In other words, if it matters whether an optimization is done or not, that
suggests to me you're writing code with undefined semantics, and the answer is
not to do so.
paul
> On Aug 1, 2023, at 12:43 PM, Bradley Lucier via Gcc <gcc@gcc.gnu.org> wrote:
>
> The Gambit Scheme->C compiler has an option to generate more efficient code
> if it knows that all tail and sibling calls in the generated C code will be
> optimized. If gcc does not, however, optimize a tail or sibling call, the
> generated C code may be incorrect (depending on circumstances).
>
> So I would like to add a warning enabled by -Wdisabled-optimization so that
> if -foptimize-sibling-calls is given and a tail or sibling call is not
> optimized, then a warning is triggered.
>
> I don't quite know where to place the warning. It would be good if there
> were one piece of code to identify all tail and sibling calls, and then
> another piece that decides whether the optimization can be performed.
>
> I see code in gcc/tree-tailcall.cc
>
> suitable_for_tail_opt_p
> suitable_for_tail_call_opt_p
>
> which are called by
>
> tree_optimize_tail_calls_1
>
> which takes an argument
>
> opt_tailcalls
>
> and it's called in one place with opt_tailcalls true and in another place
> with opt_tailcalls false.
>
> So I'm losing the plot here.
>
> There is other code dealing with tail calls in gcc/calls.cc I don't seem to
> understand at all.
>
> Any advice?
>
> Brad
