middle-end: rejects loops with nonlinear inductions and early breaks [PR113163]

We can't support nonlinear inductions other than neg when vectorizing
early breaks and iteration count is known.

For early break we currently require a peeled epilog but in these cases
we can't compute the remaining values.

gcc/ChangeLog:

	PR middle-end/113163
	* tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p):
	Reject non-linear inductions that aren't supported.

gcc/testsuite/ChangeLog:

	PR middle-end/113163
	* gcc.target/gcn/pr113163.c: New test.

1 files changed, 19 insertions, 0 deletions

diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index 927f76a..2313d26 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -2063,6 +2063,25 @@ vect_can_peel_nonlinear_iv_p (loop_vec_info loop_vinfo,
       return false;
     }
 
+  /* We can't support partial vectors and early breaks with an induction
+     type other than add or neg since we require the epilog and can't
+     perform the peeling.  The below condition mirrors that of
+     vect_gen_vector_loop_niters  where niters_vector_mult_vf_var then sets
+     step_vector to VF rather than 1.  This is what creates the nonlinear
+     IV.  PR113163.  */
+  if (LOOP_VINFO_EARLY_BREAKS (loop_vinfo)
+      && LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant ()
+      && LOOP_VINFO_USING_PARTIAL_VECTORS_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"
+			 " when VF is known and early breaks.\n");
+      return false;
+    }
+
   return true;
 }