Implement CALL_EXPR_MUST_TAIL_CALL

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.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@236514 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 2 insertions, 0 deletions

diff --git a/gcc/gimple-pretty-print.c b/gcc/gimple-pretty-print.c
index f8642684ad9..48edacce148 100644
--- a/gcc/gimple-pretty-print.c
+++ b/gcc/gimple-pretty-print.c
@@ -760,6 +760,8 @@ dump_gimple_call (pretty_printer *buffer, gcall *gs, int spc, int flags)
     pp_string (buffer, " [return slot optimization]");
   if (gimple_call_tail_p (gs))
     pp_string (buffer, " [tail call]");
+  if (gimple_call_must_tail_p (gs))
+    pp_string (buffer, " [must tail call]");
 
   if (fn == NULL)
     return;