tree-optimization/113659 - early exit vectorization and missing VUSE

The following handles the case of the main exit going to a path without
virtual use and handles it similar to the alternate exit handling.

	PR tree-optimization/113659
	* tree-vect-loop-manip.cc (slpeel_tree_duplicate_loop_to_edge_cfg):
	Handle main exit without virtual use.

	* gcc.dg/pr113659.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/pr113659.c b/gcc/testsuite/gcc.dg/pr113659.c
new file mode 100644 (file)
index 0000000..dc1091b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr113659.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-tree-sra" } */
+/* { dg-additional-options "-msse4.1" { target { x86_64-*-* i?86-*-* } } } */
+
+struct Foo {
+  int *ptr;
+};
+int Baz(struct Foo first)
+{
+  while (first.ptr)
+    if (*first.ptr++)
+      return 0;
+  __builtin_unreachable ();
+}

diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 873a28d7c560d36ddf7b1f265f598554defb5c35..3f974d6d839e32516ae316f28ca25316e43d7d86 100644 (file)
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -1708,9 +1708,23 @@ slpeel_tree_duplicate_loop_to_edge_cfg (class loop *loop, edge loop_exit,
                     LC PHI node to feed the merge PHI.  */
                  tree *res;
                  if (virtual_operand_p (new_arg))
-                   /* Use the existing virtual LC SSA from exit block.  */
-                   new_arg = gimple_phi_result
-                               (get_virtual_phi (main_loop_exit_block));
+                   {
+                     /* Use the existing virtual LC SSA from exit block.  */
+                     gphi *vphi = get_virtual_phi (main_loop_exit_block);
+                     /* ???  When the exit yields to a path without
+                        any virtual use we can miss a LC PHI for the
+                        live virtual operand.  Simply choosing the
+                        one live at the start of the loop header isn't
+                        correct, but we should get here only with
+                        early-exit vectorization which will move all
+                        defs after the main exit, so leave a temporarily
+                        wrong virtual operand in place.  This happens
+                        for gcc.dg/pr113659.c.  */
+                     if (vphi)
+                       new_arg = gimple_phi_result (vphi);
+                     else
+                       new_arg = gimple_phi_result (from_phi);
+                   }
                  else if ((res = new_phi_args.get (new_arg)))
                    new_arg = *res;
                  else