Don't peel nonlinear iv(mult or shift) for epilog when vf is not constant.

Normally when vf is not constant, it will be prevented by
vectorizable_nonlinear_inductions, but for this case, it failed going
into

    if (STMT_VINFO_RELEVANT_P (stmt_info))
      {
	need_to_vectorize = true;
	if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_induction_def
	   && ! PURE_SLP_STMT (stmt_info))
	  ok = vectorizable_induction (loop_vinfo,
				       stmt_info, NULL, NULL,
				       &cost_vec);

since the iv is never used outside of the loop, and will be dce later, so
vectorizer doesn't bother checking if it's vectorizable. it's
true but hit gcc_assert in vect_can_peel_nonlinear_iv_p when vf is not
constant. One solution is ignoring the nonlinear iv peeling if it's
!STMT_VINFO_RELEVANT_P (stmt_info) just like the upper code, the other
solution is returning false earlier in the
vect_can_peel_nonlinear_iv_p when vf is not constant, the patch chooses
the second incase there's other cases using vect_can_advance_ivs_p which
calls vect_can_peel_nonlinear_iv_p.
Also remove vect_peel_nonlinear_iv_p from
vectorizable_nonlinear_inductions.

gcc/ChangeLog:

	PR tree-optimization/108601
	* tree-vectorizer.h (vect_can_peel_nonlinear_iv_p): Removed.
	* tree-vect-loop.cc
	(vectorizable_nonlinear_induction): Remove
	vect_can_peel_nonlinear_iv_p.
	(vect_can_peel_nonlinear_iv_p): Don't peel
	nonlinear iv(mult or shift) for epilog when vf is not
	constant and moved the defination to ..
	* tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p):
	.. Here.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/pr108601.c: New test.

1 files changed, 0 insertions, 3 deletions

diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index a2aa71b..4ba6537 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -2347,9 +2347,6 @@ extern tree cse_and_gimplify_to_preheader (loop_vec_info, tree);
 /* Nonlinear induction.  */
 extern tree vect_peel_nonlinear_iv_init (gimple_seq*, tree, tree,
 					 tree, enum vect_induction_op_type);
-extern bool
-vect_can_peel_nonlinear_iv_p (loop_vec_info loop_vinfo,
-			      enum vect_induction_op_type induction_type);
 
 /* In tree-vect-slp.cc.  */
 extern void vect_slp_init (void);