https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67797
--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Andrew Pinski <pins...@gcc.gnu.org>: https://gcc.gnu.org/g:08af16bfea689d095f0d41ccfeed204178e6f8b6 commit r16-243-g08af16bfea689d095f0d41ccfeed204178e6f8b6 Author: Andrew Pinski <quic_apin...@quicinc.com> Date: Sat Apr 19 16:41:32 2025 -0700 tailcall: Support ERF_RETURNS_ARG for tailcall [PR67797] r15-6943-g9c4397cafc5ded added support to undo IPA-VRP return value optimization for tail calls, using the same code ERF_RETURNS_ARG can be supported for functions which return one of their arguments. This allows for tail calling of memset/memcpy in some cases which were not handled before. Note this is very similar to https://gcc.gnu.org/legacy-ml/gcc-patches/2016-11/msg02485.html except it has a few more checks. Also on the question of expand vs tail call here is that this path is also used by the IPA-VRP return value path and yes we get a tail call. Note in the review in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83142#c2 mentions about re-instantiate a LHS on the call & propagate to dominating uses. Even though that can be done for the ERF_RETURNS_ARG case, it is not done for the IPA-VRP return value case already so I don't think there is anything to be done there. Changes since v1: * v2: Add an useless_type_conversion_p check as suggested by Jakub and add a testcase for that. * v3: Fix the order of arguments to useless_type_conversion_p. Bootstrapped and tested on x86_64-linux-gnu. PR tree-optimization/67797 gcc/ChangeLog: * tree-tailcall.cc (find_tail_calls): Add support for ERF_RETURNS_ARG. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/tailcall-14.c: New test. * gcc.dg/tree-ssa/tailcall-15.c: New test. Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
