On Fri, Apr 25, 2025 at 09:12:45PM -0700, Andrew Pinski wrote:
> --- a/gcc/tree-tailcall.cc
> +++ b/gcc/tree-tailcall.cc
> @@ -1083,57 +1083,74 @@ find_tail_calls (basic_block bb, struct tailcall
> **ret, bool only_musttail,
> {
> bool ok = false;
> value_range val;
> - tree valr;
> - /* If IPA-VRP proves called function always returns a singleton range,
> - the return value is replaced by the only value in that range.
> - For tail call purposes, pretend such replacement didn't happen. */
> if (ass_var == NULL_TREE && !tail_recursion)
> - if (tree type = gimple_range_type (call))
> - if (tree callee = gimple_call_fndecl (call))
> - if ((INTEGRAL_TYPE_P (type)
> - || SCALAR_FLOAT_TYPE_P (type)
> - || POINTER_TYPE_P (type))
> - && useless_type_conversion_p (TREE_TYPE (TREE_TYPE (callee)),
> - type)
> - && useless_type_conversion_p (TREE_TYPE (ret_var), type)
> - && ipa_return_value_range (val, callee)
> - && val.singleton_p (&valr))
> + {
> + tree other_value = NULL_TREE;
> + /* If we have a function call that we know the return value is the
> same
> + as the argument, try the argument too. */
> + int flags = gimple_call_return_flags (call);
> + if ((flags & ERF_RETURNS_ARG) != 0
> + && (flags & ERF_RETURN_ARG_MASK) < gimple_call_num_args (call))
> + {
> + tree arg = gimple_call_arg (call, flags & ERF_RETURN_ARG_MASK);
> + if (useless_type_conversion_p (TREE_TYPE (arg), TREE_TYPE
> (ret_var)))
This should have the arguments swapped, i.e.
if (useless_type_conversion_p (TREE_TYPE (ret_var), TREE_TYPE
(arg)))
because we want to check if the type of arg is uselessly convertible to the
ret_var type (i.e. the return type).
Otherwise LGTM.
Jakub
