re PR c/91526 (Unnecessary SSE and other instructions generated when compiling…

re PR c/91526 (Unnecessary SSE and other instructions generated when compiling in C mode (vs. C++ mode))

2019-08-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91526
	* passes.def: Note that after late FRE we do TODO_update_address_taken.
	* tree-ssa-sccvn.c (pass_fre::execute): In late mode schedule
	TODO_update_address_taken.

From-SVN: r274922

gcc/ChangeLog

+2019-08-26  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/91526
+	* passes.def: Note that after late FRE we do TODO_update_address_taken.
+	* tree-ssa-sccvn.c (pass_fre::execute): In late mode schedule
+	TODO_update_address_taken.
+
 2019-08-26  Gerald Pfeifer  <gerald@pfeifer.com>
 
 	* config/i386/gmm_malloc.h: Only use <errno.h> and errno if

gcc/passes.def

@@ -313,6 +313,8 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_split_paths);
       NEXT_PASS (pass_tracer);
       NEXT_PASS (pass_fre, false /* may_iterate */);
+      /* After late FRE we rewrite no longer addressed locals into SSA
+         form if possible.  */
       NEXT_PASS (pass_thread_jumps);
       NEXT_PASS (pass_dominator, false /* may_peel_loop_headers_p */);
       NEXT_PASS (pass_strlen);

gcc/tree-ssa-sccvn.c

@@ -7312,6 +7312,11 @@ pass_fre::execute (function *fun)
   if (iterate_p)
     loop_optimizer_finalize ();
 
+  /* For late FRE after IVOPTs and unrolling, see if we can
+     remove some TREE_ADDRESSABLE and rewrite stuff into SSA.  */
+  if (!may_iterate)
+    todo |= TODO_update_address_taken;
+
   return todo;
 }