vect: Add a vect_phi_initial_value helper function

This patch adds a helper function called vect_phi_initial_value
for returning the incoming value of a given loop phi.  The main
reason for adding it is to ensure that the right preheader edge
is used when vectorising nested loops.  (PHI_ARG_DEF_FROM_EDGE
itself doesn't assert that the given edge is for the right block,
although I guess that would be good to add separately.)

gcc/
	* tree-vectorizer.h: Include tree-ssa-operands.h.
	(vect_phi_initial_value): New function.
	* tree-vect-loop.c (neutral_op_for_slp_reduction): Use it.
	(get_initial_defs_for_reduction, info_for_reduction): Likewise.
	(vect_create_epilog_for_reduction, vectorizable_reduction): Likewise.
	(vect_transform_cycle_phi, vectorizable_induction): Likewise.

1 files changed, 20 insertions, 1 deletions

diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index fa28336..e2fd360 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -27,7 +27,7 @@ typedef class _stmt_vec_info *stmt_vec_info;
 #include "tree-hash-traits.h"
 #include "target.h"
 #include "internal-fn.h"
-
+#include "tree-ssa-operands.h"
 
 /* Used for naming of new temporaries.  */
 enum vect_var_kind {
@@ -1369,6 +1369,25 @@ nested_in_vect_loop_p (class loop *loop, stmt_vec_info stmt_info)
 	  && (loop->inner == (gimple_bb (stmt_info->stmt))->loop_father));
 }
 
+/* PHI is either a scalar reduction phi or a scalar induction phi.
+   Return the initial value of the variable on entry to the containing
+   loop.  */
+
+static inline tree
+vect_phi_initial_value (gphi *phi)
+{
+  basic_block bb = gimple_bb (phi);
+  edge pe = loop_preheader_edge (bb->loop_father);
+  gcc_assert (pe->dest == bb);
+  return PHI_ARG_DEF_FROM_EDGE (phi, pe);
+}
+
+static inline tree
+vect_phi_initial_value (stmt_vec_info stmt_info)
+{
+  return vect_phi_initial_value (as_a <gphi *> (stmt_info->stmt));
+}
+
 /* Return true if STMT_INFO should produce a vector mask type rather than
    a normal nonmask type.  */