[Bug c++/106502] Three calls to __attribute__((const)) function

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106502

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Once you enable optimization a single cat () call remains (as expected).  The
FE does

9931          if (TREE_SIDE_EFFECTS (argarray[0]))
9932            argarray[0] = save_expr (argarray[0]);
9933          t = build_pointer_type (TREE_TYPE (fn));
9934          fn = build_vfn_ref (argarray[0], DECL_VINDEX (fn));

but argarray[0] doesn't have TREE_SIDE_EFFECTS set, it even has TREE_READONLY
set on the CONVERT_EXPR wrapping the call.  Note that save_expr would do
nothing on this tree as well (because TREE_READONLY and !TREE_SIDE_EFFECTS).