re PR tree-optimization/87621 (outer loop auto-vectorization fails for exponentiation code)

2018-11-09  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87621
	* tree-vect-loop.c (vectorizable_reduction): Handle reduction
	op with only phi inputs.
	* tree-ssa-loop-ch.c: Include tree-ssa-sccvn.h.
	(ch_base::copy_headers): Run CSE on copied loop headers.
	(pass_ch_vect::process_loop_p): Simplify.

	* g++.dg/vect/pr87621.cc: New testcase.

From-SVN: r265959

gcc/ChangeLog

@@ -1,3 +1,12 @@
+2018-11-09  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87621
+	* tree-vect-loop.c (vectorizable_reduction): Handle reduction
+	op with only phi inputs.
+	* tree-ssa-loop-ch.c: Include tree-ssa-sccvn.h.
+	(ch_base::copy_headers): Run CSE on copied loop headers.
+	(pass_ch_vect::process_loop_p): Simplify.
+
 2018-11-09  Alexandre Oliva <oliva@adacore.com>
 
 	* config/i386/mingw32.h (LINK_SPEC_LARGE_ADDR_AWARE): Adjust

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2018-11-09  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87621
+	* g++.dg/vect/pr87621.cc: New testcase.
+
 2018-11-09  Alexandre Oliva <aoliva@redhat.com>
 
 	PR rtl-optimization/86438

gcc/testsuite/g++.dg/vect/pr87621.cc

@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+
+extern "C" double pow(double, double);
+template <typename T>
+T pow(T x, unsigned int n)
+{
+  if (!n)
+    return 1;
+
+  T y = 1;
+  while (n > 1)
+    {
+      if (n%2)
+	y *= x;
+      x = x*x;
+      n /= 2;
+    }
+  return x*y;
+}
+
+void testVec(int* x)
+{
+  for (int i = 0; i < 8; ++i)
+    x[i] = pow(x[i], 10);
+}
+
+/* { dg-final { scan-tree-dump "OUTER LOOP VECTORIZED" "vect" { target { vect_double && vect_hw_misalign } } } } */

gcc/tree-ssa-loop-ch.c

@@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-inline.h"
 #include "tree-ssa-scopedtables.h"
 #include "tree-ssa-threadedge.h"
+#include "tree-ssa-sccvn.h"
 #include "params.h"
 
 /* Duplicates headers of loops if they are small enough, so that the statements
@@ -297,12 +298,14 @@ ch_base::copy_headers (function *fun)
   bool changed = false;
 
   if (number_of_loops (fun) <= 1)
-      return 0;
+    return 0;
 
   bbs = XNEWVEC (basic_block, n_basic_blocks_for_fn (fun));
   copied_bbs = XNEWVEC (basic_block, n_basic_blocks_for_fn (fun));
   bbs_size = n_basic_blocks_for_fn (fun);
 
+  auto_vec<std::pair<edge, loop_p> > copied;
+
   FOR_EACH_LOOP (loop, 0)
     {
       int initial_limit = PARAM_VALUE (PARAM_MAX_LOOP_HEADER_INSNS);
@@ -371,6 +374,7 @@ ch_base::copy_headers (function *fun)
 	  fprintf (dump_file, "Duplication failed.\n");
 	  continue;
 	}
+      copied.safe_push (std::make_pair (entry, loop));
 
       /* If the loop has the form "for (i = j; i < j + 10; i++)" then
 	 this copying can introduce a case where we rely on undefined
@@ -422,7 +426,28 @@ ch_base::copy_headers (function *fun)
     }
 
   if (changed)
-    update_ssa (TODO_update_ssa);
+    {
+      update_ssa (TODO_update_ssa);
+      /* After updating SSA form perform CSE on the loop header
+	 copies.  This is esp. required for the pass before
+	 vectorization since nothing cleans up copied exit tests
+	 that can now be simplified.  CSE from the entry of the
+	 region we copied till all loop exit blocks but not
+	 entering the loop itself.  */
+      for (unsigned i = 0; i < copied.length (); ++i)
+	{
+	  edge entry = copied[i].first;
+	  loop_p loop = copied[i].second;
+	  vec<edge> exit_edges = get_loop_exit_edges (loop);
+	  bitmap exit_bbs = BITMAP_ALLOC (NULL);
+	  for (unsigned j = 0; j < exit_edges.length (); ++j)
+	    bitmap_set_bit (exit_bbs, exit_edges[j]->dest->index);
+	  bitmap_set_bit (exit_bbs, loop->header->index);
+	  do_rpo_vn (cfun, entry, exit_bbs);
+	  BITMAP_FREE (exit_bbs);
+	  exit_edges.release ();
+	}
+    }
   free (bbs);
   free (copied_bbs);
 
@@ -473,24 +498,13 @@ pass_ch_vect::process_loop_p (struct loop *loop)
   if (loop->dont_vectorize)
     return false;
 
-  if (!do_while_loop_p (loop))
-    return true;
-
- /* The vectorizer won't handle anything with multiple exits, so skip.  */
+  /* The vectorizer won't handle anything with multiple exits, so skip.  */
   edge exit = single_exit (loop);
   if (!exit)
     return false;
 
-  /* Copy headers iff there looks to be code in the loop after the exit block,
-     i.e. the exit block has an edge to another block (besides the latch,
-     which should be empty).  */
-  edge_iterator ei;
-  edge e;
-  FOR_EACH_EDGE (e, ei, exit->src->succs)
-    if (!loop_exit_edge_p (loop, e)
-	&& e->dest != loop->header
-	&& e->dest != loop->latch)
-      return true;
+  if (!do_while_loop_p (loop))
+    return true;
 
   return false;
 }

gcc/tree-vect-loop.c

@@ -6075,6 +6075,10 @@ vectorizable_reduction (stmt_vec_info stmt_info, gimple_stmt_iterator *gsi,
 	    vectype_in = get_vectype_for_scalar_type (TREE_TYPE (op));
 	  break;
 	}
+      /* For a nested cycle we might end up with an operation like
+         phi_result * phi_result.  */
+      if (!vectype_in)
+	vectype_in = STMT_VINFO_VECTYPE (stmt_info);
       gcc_assert (vectype_in);
 
       if (slp_node)