tree-optimization/96698 - fix ICE when vectorizing nested cycles

This fixes vectorized PHI latch edge updating and delay it until
all of the loop is code generated to deal with the case that the
latch def is a PHI in the same block.

2020-08-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/96698
	* tree-vectorizer.h (loop_vec_info::reduc_latch_defs): New.
	(loop_vec_info::reduc_latch_slp_defs): Likewise.
	* tree-vect-stmts.c (vect_transform_stmt): Only record
	stmts to update PHI latches from, perform the update ...
	* tree-vect-loop.c (vect_transform_loop): ... here after
	vectorizing those PHIs.
	(info_for_reduction): Properly handle non-reduction PHIs.

	* gcc.dg/vect/pr96698.c: New testcase.

4 files changed, 63 insertions, 25 deletions

diff --git a/gcc/testsuite/gcc.dg/vect/pr96698.c b/gcc/testsuite/gcc.dg/vect/pr96698.c
new file mode 100644
index 0000000..1d141c1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr96698.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+
+void test(int a, int* i)
+{
+  for (; a < 5; ++a)
+    {
+      int b = 0;
+      int c = 0;
+      for (; b != -11; b--)
+	for (int d = 0; d ==0; d++)
+	  {
+	    *i += c & a;
+	    c = b;
+	  }
+    }
+}
+
+/* We should be able to vectorize the inner cycle.  */
+/* { dg-final { scan-tree-dump "OUTER LOOP VECTORIZED" "vect" { target vect_int } } } */
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index a92813e..50abb2b 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -4646,7 +4646,8 @@ info_for_reduction (vec_info *vinfo, stmt_vec_info stmt_info)
 {
   stmt_info = vect_orig_stmt (stmt_info);
   gcc_assert (STMT_VINFO_REDUC_DEF (stmt_info));
-  if (!is_a <gphi *> (stmt_info->stmt))
+  if (!is_a <gphi *> (stmt_info->stmt)
+      || !VECTORIZABLE_CYCLE_DEF (STMT_VINFO_DEF_TYPE (stmt_info)))
     stmt_info = STMT_VINFO_REDUC_DEF (stmt_info);
   gphi *phi = as_a <gphi *> (stmt_info->stmt);
   if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_double_reduction_def)
@@ -9031,6 +9032,38 @@ vect_transform_loop (loop_vec_info loop_vinfo, gimple *loop_vectorized_call)
 	    }
 	}
 
+      /* Fill in backedge defs of reductions.  */
+      for (unsigned i = 0; i < loop_vinfo->reduc_latch_defs.length (); ++i)
+	{
+	  stmt_vec_info stmt_info = loop_vinfo->reduc_latch_defs[i];
+	  stmt_vec_info orig_stmt_info = vect_orig_stmt (stmt_info);
+	  vec<gimple *> &phi_info
+	    = STMT_VINFO_VEC_STMTS (STMT_VINFO_REDUC_DEF (orig_stmt_info));
+	  vec<gimple *> &vec_stmt
+	    = STMT_VINFO_VEC_STMTS (stmt_info);
+	  gcc_assert (phi_info.length () == vec_stmt.length ());
+	  gphi *phi
+	    = dyn_cast <gphi *> (STMT_VINFO_REDUC_DEF (orig_stmt_info)->stmt);
+	  edge e = loop_latch_edge (gimple_bb (phi_info[0])->loop_father);
+	  for (unsigned j = 0; j < phi_info.length (); ++j)
+	    add_phi_arg (as_a <gphi *> (phi_info[j]),
+			 gimple_get_lhs (vec_stmt[j]), e,
+			 gimple_phi_arg_location (phi, e->dest_idx));
+	}
+      for (unsigned i = 0; i < loop_vinfo->reduc_latch_slp_defs.length (); ++i)
+	{
+	  slp_tree slp_node = loop_vinfo->reduc_latch_slp_defs[i].first;
+	  slp_tree phi_node = loop_vinfo->reduc_latch_slp_defs[i].second;
+	  gphi *phi = as_a <gphi *> (SLP_TREE_SCALAR_STMTS (phi_node)[0]->stmt);
+	  e = loop_latch_edge (gimple_bb (phi)->loop_father);
+	  gcc_assert (SLP_TREE_VEC_STMTS (phi_node).length ()
+		      == SLP_TREE_VEC_STMTS (slp_node).length ());
+	  for (unsigned j = 0; j < SLP_TREE_VEC_STMTS (phi_node).length (); ++j)
+	    add_phi_arg (as_a <gphi *> (SLP_TREE_VEC_STMTS (phi_node)[j]),
+			 vect_get_slp_vect_def (slp_node, j),
+			 e, gimple_phi_arg_location (phi, e->dest_idx));
+	}
+
       /* Stub out scalar statements that must not survive vectorization.
 	 Doing this here helps with grouped statements, or statements that
 	 are involved in patterns.  */
diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 224be01..04d202e 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -10920,8 +10920,8 @@ vect_transform_stmt (vec_info *vinfo,
   if (STMT_VINFO_TYPE (stmt_info) == store_vec_info_type)
     return is_store;
 
-  /* If this stmt defines a value used on a backedge, update the
-     vectorized PHIs.  */
+  /* If this stmt defines a value used on a backedge, record it so
+     we can update the vectorized PHIs later.  */
   stmt_vec_info orig_stmt_info = vect_orig_stmt (stmt_info);
   stmt_vec_info reduc_info;
   if (STMT_VINFO_REDUC_DEF (orig_stmt_info)
@@ -10940,30 +10940,11 @@ vect_transform_stmt (vec_info *vinfo,
 	  && (e = loop_latch_edge (gimple_bb (phi)->loop_father))
 	  && (PHI_ARG_DEF_FROM_EDGE (phi, e)
 	      == gimple_get_lhs (orig_stmt_info->stmt)))
-	{
-	  vec<gimple *> &phi_info
-	    = STMT_VINFO_VEC_STMTS (STMT_VINFO_REDUC_DEF (orig_stmt_info));
-	  vec<gimple *> &vec_stmt
-	    = STMT_VINFO_VEC_STMTS (stmt_info);
-	  gcc_assert (phi_info.length () == vec_stmt.length ());
-	  for (unsigned i = 0; i < phi_info.length (); ++i)
-	    add_phi_arg (as_a <gphi *> (phi_info[i]),
-			 gimple_get_lhs (vec_stmt[i]), e,
-			 gimple_phi_arg_location (phi, e->dest_idx));
-	}
+	as_a <loop_vec_info> (vinfo)->reduc_latch_defs.safe_push (stmt_info);
       else if (slp_node
 	       && slp_node != slp_node_instance->reduc_phis)
-	{
-	  slp_tree phi_node = slp_node_instance->reduc_phis;
-	  gphi *phi = as_a <gphi *> (SLP_TREE_SCALAR_STMTS (phi_node)[0]->stmt);
-	  e = loop_latch_edge (gimple_bb (phi)->loop_father);
-	  gcc_assert (SLP_TREE_VEC_STMTS (phi_node).length ()
-		      == SLP_TREE_VEC_STMTS (slp_node).length ());
-	  for (unsigned i = 0; i < SLP_TREE_VEC_STMTS (phi_node).length (); ++i)
-	    add_phi_arg (as_a <gphi *> (SLP_TREE_VEC_STMTS (phi_node)[i]),
-			 vect_get_slp_vect_def (slp_node, i),
-			 e, gimple_phi_arg_location (phi, e->dest_idx));
-	}
+	as_a <loop_vec_info> (vinfo)->reduc_latch_slp_defs.safe_push
+	    (std::make_pair (slp_node, slp_node_instance->reduc_phis));
     }
 
   /* Handle stmts whose DEF is used outside the loop-nest that is
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 8551b68..f36e2ad 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -627,6 +627,11 @@ public:
      stmt in the chain.  */
   auto_vec<stmt_vec_info> reduction_chains;
 
+  /* The vectorized stmts defining the latch values of the reduction
+     they are involved with.  */
+  auto_vec<stmt_vec_info> reduc_latch_defs;
+  auto_vec<std::pair<slp_tree, slp_tree> > reduc_latch_slp_defs;
+
   /* Cost vector for a single scalar iteration.  */
   auto_vec<stmt_info_for_cost> scalar_cost_vec;