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.

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.
+
 2020-01-16  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_split_sve_subreg_move): Apply

gcc/testsuite/ChangeLog

+2020-01-16  Andre Vieira  <andre.simoesdiasvieira@arm.com>
+
+	PR tree-optimization/92429
+	* gcc.dg/vect/pr92429.c: New test.
+
 2020-01-16  Tobias Burnus  <tobias@codesourcery.com>
 
 	PR fortran/93253

gcc/tree-ssa-loop-niter.c

@@ -1934,7 +1934,8 @@ number_of_iterations_cond (class loop *loop,
 
 tree
 simplify_replace_tree (tree expr, tree old, tree new_tree,
-		       tree (*valueize) (tree, void*), void *context)
+		       tree (*valueize) (tree, void*), void *context,
+		       bool do_fold)
 {
   unsigned i, n;
   tree ret = NULL_TREE, e, se;
@@ -1966,7 +1967,7 @@ simplify_replace_tree (tree expr, tree old, tree new_tree,
   for (i = 0; i < n; i++)
     {
       e = TREE_OPERAND (expr, i);
-      se = simplify_replace_tree (e, old, new_tree, valueize, context);
+      se = simplify_replace_tree (e, old, new_tree, valueize, context, do_fold);
       if (e == se)
 	continue;
 
@@ -1976,7 +1977,7 @@ simplify_replace_tree (tree expr, tree old, tree new_tree,
       TREE_OPERAND (ret, i) = se;
     }
 
-  return (ret ? fold (ret) : expr);
+  return (ret ? (do_fold ? fold (ret) : ret) : expr);
 }
 
 /* Expand definitions of ssa names in EXPR as long as they are simple

gcc/tree-ssa-loop-niter.h

@@ -58,7 +58,7 @@ extern void free_numbers_of_iterations_estimates (class loop *);
 extern void free_numbers_of_iterations_estimates (function *);
 extern tree simplify_replace_tree (tree, tree,
 				   tree, tree (*)(tree, void *) = NULL,
-				   void * = NULL);
+				   void * = NULL, bool do_fold = true);
 extern void substitute_in_loop_info (class loop *, tree, tree);
 
 #endif /* GCC_TREE_SSA_LOOP_NITER_H */

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);
 	    }
 	}