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, 0 deletions

diff --git a/gcc/opts.c b/gcc/opts.c
index f159bb3..25282f7 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -575,6 +575,7 @@ static const struct default_options default_options_table[] =
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_finline_functions_called_once, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fmove_loop_invariants, NULL, 1 },
+    { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fmove_loop_stores, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fssa_phiopt, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fipa_modref, NULL, 1 },
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_ftree_bit_ccp, NULL, 1 },