subreg: Add -fsplit-wide-types-early (PR88233)

Currently the second lower-subreg pass is run right before RA.  This
is much too late to be very useful.  At least for targets that do not
have RTL patterns for operations on multi-register modes it is a lot
better to split patterns earlier, before combine and all related
passes.

This adds an option -fsplit-wide-types-early that does that, and
enables it by default for rs6000.


	PR rtl-optimization/88233
	* common.opt (fsplit-wide-types-early): New option.
	* common/config/rs6000/rs6000-common.c
	(rs6000_option_optimization_table): Add OPT_fsplit_wide_types_early for
	OPT_LEVELS_ALL.
	* doc/invoke.texi (Optimization Options): Add -fsplit-wide-types-early.
	* lower-subreg.c (pass_lower_subreg2::gate): Add test for
	flag_split_wide_types_early.
	(pass_data_lower_subreg3): New.
	(pass_lower_subreg3): New.
	(make_pass_lower_subreg3): New.
	* passes.def (pass_lower_subreg2): Move after the loop passes.
	(pass_lower_subreg3): New, inserted where pass_lower_subreg2 was.
	* tree-pass.h (make_pass_lower_subreg2): Move up, to its new place in
	the pass pipeline; its previous place is taken by ...
	(make_pass_lower_subreg3): ... this.

From-SVN: r273240

1 files changed, 45 insertions, 1 deletions

diff --git a/gcc/lower-subreg.c b/gcc/lower-subreg.c
index 4f68a7381b7..e1418e5ec51 100644
--- a/gcc/lower-subreg.c
+++ b/gcc/lower-subreg.c
@@ -1801,7 +1801,8 @@ public:
   {}
 
   /* opt_pass methods: */
-  virtual bool gate (function *) { return flag_split_wide_types != 0; }
+  virtual bool gate (function *) { return flag_split_wide_types
+					  && flag_split_wide_types_early; }
   virtual unsigned int execute (function *)
     {
       decompose_multiword_subregs (true);
@@ -1817,3 +1818,46 @@ make_pass_lower_subreg2 (gcc::context *ctxt)
 {
   return new pass_lower_subreg2 (ctxt);
 }
+
+/* Implement third lower subreg pass.  */
+
+namespace {
+
+const pass_data pass_data_lower_subreg3 =
+{
+  RTL_PASS, /* type */
+  "subreg3", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  TV_LOWER_SUBREG, /* tv_id */
+  0, /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  TODO_df_finish, /* todo_flags_finish */
+};
+
+class pass_lower_subreg3 : public rtl_opt_pass
+{
+public:
+  pass_lower_subreg3 (gcc::context *ctxt)
+    : rtl_opt_pass (pass_data_lower_subreg3, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  virtual bool gate (function *) { return flag_split_wide_types
+					  && !flag_split_wide_types_early; }
+  virtual unsigned int execute (function *)
+    {
+      decompose_multiword_subregs (true);
+      return 0;
+    }
+
+}; // class pass_lower_subreg3
+
+} // anon namespace
+
+rtl_opt_pass *
+make_pass_lower_subreg3 (gcc::context *ctxt)
+{
+  return new pass_lower_subreg3 (ctxt);
+}