PR tree-optimization/92429 do not fold when updating epilogue statements

This patch addresses the problem reported in PR92429.  When creating an
epilogue for vectorization we have to replace the SSA_NAMEs in the
PATTERN_DEF_SEQs and RELATED_STMTs of the epilogue's loop_vec_infos. When doing
this we were using simplify_replace_tree which always folds the replacement.
This may lead to a different tree-node than the one which was analyzed in
vect_loop_analyze.  In turn the new tree-node may require a different
vectorization than the one we had prepared for which caused the ICE in
question.

gcc/ChangeLog:
2020-01-16  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	PR tree-optimization/92429
	* tree-ssa-loop-niter.h (simplify_replace_tree): Add parameter.
	* tree-ssa-loop-niter.c (simplify_replace_tree): Add parameter to
	control folding.
	* tree-vect-loop.c (update_epilogue_vinfo): Do not fold when replacing
	tree.

gcc/testsuite/ChangeLog:
2020-01-16  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	PR tree-optimization/92429
	* gcc.dg/vect/pr92429.c: New test.

1 files changed, 6 insertions, 1 deletions

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index 8e318a0..e5fb434 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -8434,8 +8434,13 @@ update_epilogue_loop_vinfo (class loop *epilogue, tree advance)
 	    gimple_set_op (stmt, j, *new_op);
 	  else
 	    {
+	      /* PR92429: The last argument of simplify_replace_tree disables
+		 folding when replacing arguments.  This is required as
+		 otherwise you might end up with different statements than the
+		 ones analyzed in vect_loop_analyze, leading to different
+		 vectorization.  */
 	      op = simplify_replace_tree (op, NULL_TREE, NULL_TREE,
-				     &find_in_mapping, &mapping);
+					  &find_in_mapping, &mapping, false);
 	      gimple_set_op (stmt, j, op);
 	    }
 	}