PR middle-end/53590

	* common.opt (-fdelete-dead-exceptions): New switch.
	* doc/invoke.texi (Code Gen Options): Document it.
	* cse.c (count_reg_usage) <CALL_INSN>: Use !insn_nothrow_p in lieu of
	insn_could_throw_p predicate.  Do not skip an insn that could throw
	if dead exceptions can be deleted.
	(insn_live_p): Likewise, do not return true in that case.
	* dce.c (can_alter_cfg): New flag.
	(deletable_insn_p): Do not return false for an insn that can throw if
	the CFG can be altered and dead exceptions can be deleted.
	(init_dce): Set can_alter_cfg to false for fast DCE, true otherwise.
	* dse.c (scan_insn): Use !insn_nothrow_p in lieu of insn_could_throw_
	predicate. Do not preserve an insn that could throw if dead exceptions
	can be deleted.
	* function.h (struct function): Add can_delete_dead_exceptions flag.
	* function.c (allocate_struct_function): Set it.
	* lto-streamer-in.c (input_struct_function_base): Stream it.
	* lto-streamer-out.c (input_struct_function_base): Likewise.
	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Do not mark a
	statement that could throw as necessary if dead exceptions can be
	deleted.
ada/
	* gcc-interface/misc.c (gnat_init_options_struct): Set
	opts->x_flag_delete_dead_exceptions to 1.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@188651 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 4 insertions, 2 deletions

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 1d72e06fe76..8763cfb28d2 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -272,8 +272,10 @@ static void
 mark_stmt_if_obviously_necessary (gimple stmt, bool aggressive)
 {
   /* With non-call exceptions, we have to assume that all statements could
-     throw.  If a statement may throw, it is inherently necessary.  */
-  if (cfun->can_throw_non_call_exceptions && stmt_could_throw_p (stmt))
+     throw.  If a statement could throw, it can be deemed necessary.  */
+  if (cfun->can_throw_non_call_exceptions
+      && !cfun->can_delete_dead_exceptions
+      && stmt_could_throw_p (stmt))
     {
       mark_stmt_necessary (stmt, true);
       return;