tree 1db56f95d2f293cbc349ade877c34449cbbeef89
parent b15c9d7dd22d3ffd7046397172902f11f71e4fe7
author Joshua Haberman <jhaberman@gmail.com> 1618530559 -0700
committer Copybara-Service <copybara-worker@google.com> 1618600603 -0700

Implemented [[clang::musttail]] attribute for guaranteed tail calls.

This is a Clang-only change and depends on the existing "musttail"
support already implemented in LLVM.

The [[clang::musttail]] attribute goes on a return statement, not
a function definition. There are several constraints that the user
must follow when using [[clang::musttail]], and these constraints
are verified by Sema.

Tail calls are supported on regular function calls, calls through a
function pointer, member function calls, and even pointer to member.

Future work would be to throw a warning if a users tries to pass
a pointer or reference to a local variable through a musttail call.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D99517

GitOrigin-RevId: 8344675908424ee532d4ae30e5043c5a5834e02c