From: Christopher Bazley <[email protected]>

vect_create_vectorized_promotion_stmts no longer pushes
more stmts than implied by vect_get_num_copies because it could
previously overrun the number of slots allocated for an SLP node
(based on its number of lanes and type). e.g., four defs were
pushed for a promotion of V8HI to V2DI (8/2=4) even if only two
lanes of the V8HI were active. Allowing it later caused ICE in
vectorizable_operation for a parent node, because binary ops
require both operands to be the same length.

Since promotion no longer produces redundant definitions,
vectorizable_conversion also had to be modified so that demotion no
longer relies on an even number of defs being produced. If
necessary, it now pushes a single constant zero def.

gcc/ChangeLog:

        * tree-vect-stmts.cc (vect_create_vectorized_promotion_stmts):
        Require an SLP tree node to be passed by the caller, for use
        by vect_get_num_copies.  Stop pushing more stmts than implied
        by vect_get_num_copies.
        (vectorizable_conversion): Pass SLP tree node to
        vect_create_vectorized_promotion_stmts.  Demotion no longer
        relies on an even number of definitions being produced by
        promotion. If necessary, push a single constant zero
        definition.
---
 gcc/tree-vect-stmts.cc | 61 ++++++++++++++++++++++++++----------------
 1 file changed, 38 insertions(+), 23 deletions(-)

diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 700b3e7e0686..5ce9db48e286 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -5167,7 +5167,7 @@ vect_create_vectorized_demotion_stmts (vec_info *vinfo, 
vec<tree> *vec_oprnds,
    call the function recursively.  */
 
 static void
-vect_create_vectorized_promotion_stmts (vec_info *vinfo,
+vect_create_vectorized_promotion_stmts (vec_info *vinfo, slp_tree slp_node,
                                        vec<tree> *vec_oprnds0,
                                        vec<tree> *vec_oprnds1,
                                        stmt_vec_info stmt_info, tree vec_dest,
@@ -5180,37 +5180,39 @@ vect_create_vectorized_promotion_stmts (vec_info *vinfo,
   gimple *new_stmt1, *new_stmt2;
   vec<tree> vec_tmp = vNULL;
 
-  vec_tmp.create (vec_oprnds0->length () * 2);
+  const unsigned ncopies = vect_get_num_copies (vinfo, slp_node);
+  vec_tmp.create (ncopies);
+  gcc_assert (vec_oprnds0->length () <= ncopies);
   FOR_EACH_VEC_ELT (*vec_oprnds0, i, vop0)
     {
+      if (vec_tmp.length () >= ncopies)
+       break;
+
       if (op_type == binary_op)
        vop1 = (*vec_oprnds1)[i];
       else
        vop1 = NULL_TREE;
 
       /* Generate the two halves of promotion operation.  */
-      new_stmt1 = vect_gen_widened_results_half (vinfo, ch1, vop0, vop1,
-                                                op_type, vec_dest, gsi,
-                                                stmt_info);
-      new_stmt2 = vect_gen_widened_results_half (vinfo, ch2, vop0, vop1,
-                                                op_type, vec_dest, gsi,
-                                                stmt_info);
-      if (is_gimple_call (new_stmt1))
-       {
-         new_tmp1 = gimple_call_lhs (new_stmt1);
-         new_tmp2 = gimple_call_lhs (new_stmt2);
-       }
-      else
+      new_stmt1
+       = vect_gen_widened_results_half (vinfo, ch1, vop0, vop1, op_type,
+                                        vec_dest, gsi, stmt_info);
+      new_tmp1 = is_gimple_call (new_stmt1) ? gimple_call_lhs (new_stmt1)
+                                           : gimple_assign_lhs (new_stmt1);
+      vec_tmp.quick_push (new_tmp1);
+
+      if (vec_tmp.length () < ncopies)
        {
-         new_tmp1 = gimple_assign_lhs (new_stmt1);
-         new_tmp2 = gimple_assign_lhs (new_stmt2);
+         new_stmt2
+           = vect_gen_widened_results_half (vinfo, ch2, vop0, vop1, op_type,
+                                            vec_dest, gsi, stmt_info);
+         new_tmp2 = is_gimple_call (new_stmt2) ? gimple_call_lhs (new_stmt2)
+                                               : gimple_assign_lhs (new_stmt2);
+         vec_tmp.quick_push (new_tmp2);
        }
-
-      /* Store the results for the next step.  */
-      vec_tmp.quick_push (new_tmp1);
-      vec_tmp.quick_push (new_tmp2);
     }
 
+  gcc_assert (vec_tmp.length () <= ncopies);
   vec_oprnds0->release ();
   *vec_oprnds0 = vec_tmp;
 }
@@ -5832,12 +5834,15 @@ vectorizable_conversion (vec_info *vinfo,
                                             stmt_info, this_dest, gsi, c1,
                                             op_type);
          else
-           vect_create_vectorized_promotion_stmts (vinfo, &vec_oprnds0,
-                                                   &vec_oprnds1, stmt_info,
-                                                   this_dest, gsi,
+           vect_create_vectorized_promotion_stmts (vinfo, slp_node,
+                                                   &vec_oprnds0, &vec_oprnds1,
+                                                   stmt_info, this_dest, gsi,
                                                    c1, c2, op_type);
        }
 
+      gcc_assert (vec_oprnds0.length ()
+                 == vect_get_num_copies (vinfo, slp_node));
+
       FOR_EACH_VEC_ELT (vec_oprnds0, i, vop0)
        {
          gimple *new_stmt;
@@ -5861,6 +5866,16 @@ vectorizable_conversion (vec_info *vinfo,
         generate more than one vector stmt - i.e - we need to "unroll"
         the vector stmt by a factor VF/nunits.  */
       vect_get_vec_defs (vinfo, slp_node, op0, &vec_oprnds0);
+
+      /* Promotion no longer produces redundant defs (since support was
+       added for length/mask-predicated BB SLP of awkward-sized groups),
+       therefore demotion now has to handle that case too.  */
+      if (vec_oprnds0.length () % 2 != 0)
+       {
+         tree vectype = TREE_TYPE (vec_oprnds0[0]);
+         vec_oprnds0.safe_push (build_zero_cst (vectype));
+       }
+
       /* Arguments are ready.  Create the new vector stmts.  */
       if (cvt_type && modifier == NARROW_DST)
        FOR_EACH_VEC_ELT (vec_oprnds0, i, vop0)
-- 
2.54.0

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