tailc, expand: Tail call -fdump-{tree-tailc,expand-details} changes [PR119718]

The following patch makes some adjustments so that users can analyze what
calls weren't tail called even without using musttail attribute (though I'm
still not convinced it should be a warning, because we don't distinguish
between calls in return call (...); statements vs. calls that just happened
to end up in tail positions because something has been optimized away etc.

E.g. for
int foo (int, int, int, int, int, int, int);
int bar (int);
void qux (int *);

int
baz (int x)
{
  if (x)
    return foo (1, 2, 3, 4, 5, 6, 7);
  else
    {
      int y;
      qux (&y);
      return bar (x);
    }
}
./xgcc -B ./ -S -O2 -fdump-{tree-tailc,rtl-expand}-details pr119718.c ; grep -B1 '^\(;; \)\?Cannot tail-call:' pr119718.c.*
pr119718.c.222t.tailc-_7 = bar (0);
pr119718.c.222t.tailc:Cannot tail-call: call invocation refers to locals
--
pr119718.c.270r.expand-;; foo (1, 2, 3, 4, 5, 6, 7) [tail call]
pr119718.c.270r.expand:;; Cannot tail-call: callee required more stack slots than the caller

The changes are:
1) in tailc pass use wording more consistent with the musttail error wording
2) do it only in *-details dump
3) add similar diagnostics on the expand side, but this time only for the
   CALL_EXPR_TAILCALL calls, if something wasn't marked that way, it is up
   to tailc pass to emit message about it, if it was and it still can't be
   tail called, let it tell users about that; in this case I need
   to use the ;; prefix because it will appear in the middle of
   the IL dump and ;; is what is used for such purposes in other spots
4) I've tried to improve formatting of the maybe_error_musttail and
   maybe_complain_about_tail_call calls

2025-04-12  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/119718
	* tree-tailcall.cc (maybe_error_musttail): Only dump into dump_file
	if dump_flags & TDF_DETAILS.  Use "Cannot tail-call: " prefix instead
	of "Cannot convert: ".
	(find_tail_calls, tree_optimize_tail_calls_1): Formatting fixes
	for maybe_error_musttail calls.
	* calls.cc (maybe_complain_about_tail_call): Emit also a message
	into dump_file when dump_flags & TDF_DETAILS for CALL_EXPR_TAILCALL
	calls.
	(initialize_argument_information): Formatting fix for
	maybe_complain_about_tail_call calls.
	(can_implement_as_sibling_call_p, expand_call): Likewise.

0 files changed, 0 insertions, 0 deletions