add -fmove-loop-stores option to control GIMPLE loop store-motion

This adds the -fmove-loop-stores option, mainly as a way to disable
the store-motion part of GIMPLE invariant motion (-ftree-loop-im)
which is enabled by default.  It might be sensible to turn off
-fmove-loop-stores at -O1 since it can result in compile-time
as well as memory usage issues but this patch tries to preserve
existing behavior besides introducing the new option with the
exception of -Og where I've disabled it.

Controlling store-motion has been made easy by earlier refactoring
for the invariant motion only use after loop interchange.

2021-07-02  Richard Biener  <rguenther@suse.de>

	* doc/invoke.texi (fmove-loop-stores): Document.
	* common.opt (fmove-loop-stores): New option.
	* opts.c (default_options_table): Enable -fmove-loop-stores
	at -O1 but not -Og.
	* tree-ssa-loop-im.c (pass_lim::execute): Pass
	flag_move_loop_stores instead of true to
	loop_invariant_motion_in_fun.

1 files changed, 1 insertions, 1 deletions

diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
index e7a3050..9ac390b 100644
--- a/gcc/tree-ssa-loop-im.c
+++ b/gcc/tree-ssa-loop-im.c
@@ -3258,7 +3258,7 @@ pass_lim::execute (function *fun)
 
   if (number_of_loops (fun) <= 1)
     return 0;
-  unsigned int todo = loop_invariant_motion_in_fun (fun, true);
+  unsigned int todo = loop_invariant_motion_in_fun (fun, flag_move_loop_stores);
 
   if (!in_loop_pipeline)
     loop_optimizer_finalize ();