Let ldist ignore clobbers

2019-05-03  Marc Glisse  <marc.glisse@inria.fr>

	PR tree-optimization/90269
gcc/
	* tree-loop-distribution.c (find_seed_stmts_for_distribution):
	Ignore clobbers.

gcc/testsuite/
	* g++.dg/tree-ssa/ldist-1.C: New file.

From-SVN: r270852

gcc/ChangeLog

+2019-05-03  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR tree-optimization/90269
+	* tree-loop-distribution.c (find_seed_stmts_for_distribution):
+	Ignore clobbers.
+
 2019-05-03  Martin Liska  <mliska@suse.cz>
 
 	* hash-map.h: Add is_empty function.

gcc/testsuite/ChangeLog

+2019-05-03  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR tree-optimization/90269
+	* g++.dg/tree-ssa/ldist-1.C: New file.
+
 2019-05-03  Richard Biener  <rguenther@suse.de>
 
 	* gcc.dg/vect/slp-reduc-sad-2.c: New testcase.

gcc/testsuite/g++.dg/tree-ssa/ldist-1.C

+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-ldist-details" } */
+
+#include <new>
+struct T {
+    int* p;
+    T(T const&t):p(t.p){}
+};
+void f(T*__restrict a,T*__restrict b){
+    for(int i=0;i<1024;++i){
+	new(a+i)T(b[i]);
+	b[i].~T();
+    }
+}
+
+/* { dg-final { scan-tree-dump "generated memcpy" "ldist" } } */

gcc/tree-loop-distribution.c

@@ -3040,6 +3040,10 @@ find_seed_stmts_for_distribution (struct loop *loop, vec<gimple *> *work_list)
 	{
 	  gimple *stmt = gsi_stmt (gsi);
 
+	  /* Ignore clobbers, they do not have true side effects.  */
+	  if (gimple_clobber_p (stmt))
+	    continue;
+
 	  /* If there is a stmt with side-effects bail out - we
 	     cannot and should not distribute this loop.  */
 	  if (gimple_has_side_effects (stmt))