[gcc(refs/users/wschmidt/heads/builtins3)] tree-optimization/96698 - fix ICE when vectorizing nested cycles

[gcc(refs/users/wschmidt/heads/builtins3)] tree-optimization/96698 - fix ICE when vectorizing nested cycles

[William Schmidt]

https://gcc.gnu.org/g:2130efe6ac7beba72d289e3dd145daa10aeaed54

commit 2130efe6ac7beba72d289e3dd145daa10aeaed54
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Aug 26 15:12:17 2020 +0200

    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.

Diff:
---
 gcc/testsuite/gcc.dg/vect/pr96698.c | 19 +++++++++++++++++++
 gcc/tree-vect-loop.c                | 35 ++++++++++++++++++++++++++++++++++-
 gcc/tree-vect-stmts.c               | 29 +++++------------------------
 gcc/tree-vectorizer.h               |  5 +++++
 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 00000000000..1d141c1dfff
--- /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 a92813eb2ac..50abb2b2f3c 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 224be018af9..04d202e670e 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 8551b686613..f36e2ad9626 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;