tree-optimization/114485 - neg induction with partial vectors

We can't use vect_update_ivs_after_vectorizer for partial vectors,
the following fixes vect_can_peel_nonlinear_iv_p accordingly.

	PR tree-optimization/114485
	* tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p):
	vect_step_op_neg isn't OK for partial vectors but only
	for unknown niter.

	* gcc.dg/vect/pr114485.c: New testcase.

2 files changed, 25 insertions, 7 deletions

diff --git a/gcc/testsuite/gcc.dg/vect/pr114485.c b/gcc/testsuite/gcc.dg/vect/pr114485.c
new file mode 100644
index 0000000..6536806e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr114485.c
@@ -0,0 +1,18 @@
+#include "tree-vect.h"
+
+int b, c = 8, d;
+int e[23];
+int main()
+{
+  check_vect ();
+
+  int *h = e;
+  for (int i = 1; i < b + 21; i += 2)
+    {
+      c *= -1;
+      d = h[i] ? i : 0;
+    }
+  if (c != 8)
+    abort ();
+  return 0;
+}
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 56a6d8e..8d9b533 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -2128,18 +2128,18 @@ vect_can_peel_nonlinear_iv_p (loop_vec_info loop_vinfo,
      For shift, when shift mount >= precision, there would be UD.
      For mult, don't known how to generate
      init_expr * pow (step, niters) for variable niters.
-     For neg, it should be ok, since niters of vectorized main loop
+     For neg unknown niters are ok, since niters of vectorized main loop
      will always be multiple of 2.
-     See also PR113163 and PR114196.  */
-  if ((!LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant ()
-       || LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
-       || !LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo))
-      && induction_type != vect_step_op_neg)
+     See also PR113163,  PR114196 and PR114485.  */
+  if (!LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant ()
+      || LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
+      || (!LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
+	  && induction_type != vect_step_op_neg))
     {
       if (dump_enabled_p ())
 	dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
 			 "Peeling for epilogue is not supported"
-			 " for nonlinear induction except neg"
+			 " for this nonlinear induction"
 			 " when iteration count is unknown or"
 			 " when using partial vectorization.\n");
       return false;