https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94359
--- Comment #13 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Iain D Sandoe <ia...@gcc.gnu.org>: https://gcc.gnu.org/g:a126a1577ffcbf62d97723b35d343bdff014bb40 commit r10-7724-ga126a1577ffcbf62d97723b35d343bdff014bb40 Author: Iain Sandoe <i...@sandoe.co.uk> Date: Tue Apr 14 20:37:12 2020 +0100 coroutines: Fix compile error with symmetric transfers [PR94359] For symmetric transfers to work with C++20 coroutines, it is currently necessary to tail call the callee coroutine from resume method of the caller coroutine. The current codegen marks these resume calls as "MUST_TAIL_CALL" to indicate that the tail call is required for correctness. Unfortunately, several targets have ABI constraints that prevent an indirect tail-call, which results in the PRs compile error. The change here tests the target sibcall hook for the resume expression and only marks it as requiring a tail call if that's supported. This doesn't fix the underlying problem; that really a solution is needed to allow the tail-calls (or equivalent) to take place - but that will be deferred until next stage 1. gcc/cp/ChangeLog: 2020-04-14 Iain Sandoe <i...@sandoe.co.uk> PR c++/94359 * coroutines.cc (build_actor_fn): Check that the target can support the resume tailcall before mandating it. gcc/testsuite/ChangeLog: 2020-04-14 Iain Sandoe <i...@sandoe.co.uk> PR c++/94359 * g++.dg/coroutines/torture/symmetric-transfer-00-basic.C: Expect a run fail for targets without arbitrary indirect tail-calls.
