This patch implements support for marking CALL_EXPRs
as being mandatory for tail-call-optimization. expand_call
tries harder to perform the optimization on such CALL_EXPRs,
and issues an error if it fails.
Currently this flag isn't accessible from any frontend,
so the patch uses a plugin for testing the functionality.
gcc/ChangeLog:
* calls.c (maybe_complain_about_tail_call): New function.
(initialize_argument_information): Call
maybe_complain_about_tail_call when clearing *may_tailcall.
(can_implement_as_sibling_call_p): Call
maybe_complain_about_tail_call when returning false.
(expand_call): Read CALL_EXPR_MUST_TAIL_CALL and, if set,
ensure try_tail_call is set. Call maybe_complain_about_tail_call
if tail-call optimization fails.
* cfgexpand.c (expand_call_stmt): Initialize
CALL_EXPR_MUST_TAIL_CALL from gimple_call_must_tail_p.
* gimple-pretty-print.c (dump_gimple_call): Dump
gimple_call_must_tail_p.
* gimple.c (gimple_build_call_from_tree): Call
gimple_call_set_must_tail with the value of
CALL_EXPR_MUST_TAIL_CALL.
* gimple.h (enum gf_mask): Add GF_CALL_MUST_TAIL_CALL.
(gimple_call_set_must_tail): New function.
(gimple_call_must_tail_p): New function.
* print-tree.c (print_node): Update printing of TREE_STATIC
to reflect its use for CALL_EXPR_MUST_TAIL_CALL.
* tree-core.h (struct tree_base): Add MUST_TAIL_CALL to the
trailing comment listing applicable flags.
* tree.h (CALL_EXPR_MUST_TAIL_CALL): New macro.
gcc/testsuite/ChangeLog:
* gcc.dg/plugin/must-tail-call-1.c: New test case.
* gcc.dg/plugin/must-tail-call-2.c: New test case.
* gcc.dg/plugin/must_tail_call_plugin.c: New file.
* gcc.dg/plugin/plugin.exp (plugin_test_list): Add the above.
From-SVN: r236514
