8334724: C2: remove PhaseIdealLoop::cast_incr_before_loop()

Reviewed-by: chagedorn, kvn

Author: rwestrel

src/hotspot/share/opto/loopTransform.cpp

@@ -1309,19 +1309,6 @@ Node *PhaseIdealLoop::clone_up_backedge_goo(Node *back_ctrl, Node *preheader_ctr
   return n;
 }
 
-Node* PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
-  Node* castii = new CastIINode(ctrl, incr, TypeInt::INT, ConstraintCastNode::UnconditionalDependency);
-  register_new_node(castii, ctrl);
-  for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {
-    Node* n = incr->fast_out(i);
-    if (n->is_Phi() && n->in(0) == loop) {
-      int nrep = n->replace_edge(incr, castii, &_igvn);
-      return castii;
-    }
-  }
-  return nullptr;
-}
-
 #ifdef ASSERT
 void PhaseIdealLoop::ensure_zero_trip_guard_proj(Node* node, bool is_main_loop) {
   assert(node->is_IfProj(), "must be the zero trip guard If node");
@@ -1680,14 +1667,11 @@ void PhaseIdealLoop::insert_pre_post_loops(IdealLoopTree *loop, Node_List &old_n
   // variable value and the induction variable Phi to preserve correct
   // dependencies.
 
-  // CastII for the main loop:
-  Node* castii = cast_incr_before_loop(pre_incr, min_taken, main_head);
-  assert(castii != nullptr, "no castII inserted");
   assert(post_head->in(1)->is_IfProj(), "must be zero-trip guard If node projection of the post loop");
-  copy_assertion_predicates_to_main_loop(pre_head, castii, stride, outer_loop, outer_main_head, dd_main_head,
+  copy_assertion_predicates_to_main_loop(pre_head, pre_incr, stride, outer_loop, outer_main_head, dd_main_head,
                                          idx_before_pre_post, idx_after_post_before_pre, min_taken, post_head->in(1),
                                          old_new);
-  copy_assertion_predicates_to_post_loop(outer_main_head, post_head, post_incr, stride);
+  copy_assertion_predicates_to_post_loop(outer_main_head, post_head, stride);
 
   // Step B4: Shorten the pre-loop to run only 1 iteration (for now).
   // RCE and alignment may change this later.
@@ -1812,7 +1796,7 @@ void PhaseIdealLoop::insert_vector_post_loop(IdealLoopTree *loop, Node_List &old
   // In this case we throw away the result as we are not using it to connect anything else.
   CountedLoopNode *post_head = nullptr;
   insert_post_loop(loop, old_new, main_head, main_end, incr, limit, post_head);
-  copy_assertion_predicates_to_post_loop(main_head->skip_strip_mined(), post_head, incr, main_head->stride());
+  copy_assertion_predicates_to_post_loop(main_head->skip_strip_mined(), post_head, main_head->stride());
 
   // It's difficult to be precise about the trip-counts
   // for post loops.  They are usually very short,
@@ -1915,10 +1899,6 @@ Node *PhaseIdealLoop::insert_post_loop(IdealLoopTree* loop, Node_List& old_new,
     }
   }
 
-  // CastII for the new post loop:
-  incr = cast_incr_before_loop(zer_opaq->in(1), zer_taken, post_head);
-  assert(incr != nullptr, "no castII inserted");
-
   return new_main_exit;
 }
 
@@ -1934,12 +1914,6 @@ bool IdealLoopTree::is_invariant(Node* n) const {
 // to the new stride.
 void PhaseIdealLoop::update_main_loop_assertion_predicates(Node* ctrl, CountedLoopNode* loop_head, Node* init,
                                                            const int stride_con) {
-  if (init->is_CastII()) {
-    // skip over the cast added by PhaseIdealLoop::cast_incr_before_loop() when pre/post/main loops are created because
-    // it can get in the way of type propagation
-    assert(init->as_CastII()->carry_dependency() && loop_head->skip_assertion_predicates_with_halt() == init->in(0), "casted iv phi from pre loop expected");
-    init = init->in(1);
-  }
   Node* entry = ctrl;
   Node* prev_proj = ctrl;
   LoopNode* outer_loop_head = loop_head->skip_strip_mined();
@@ -1988,7 +1962,9 @@ void PhaseIdealLoop::update_main_loop_assertion_predicates(Node* ctrl, CountedLo
 // Go over the Assertion Predicates of the main loop and make a copy for the post loop with its initial iv value and
 // stride as inputs.
 void PhaseIdealLoop::copy_assertion_predicates_to_post_loop(LoopNode* main_loop_head, CountedLoopNode* post_loop_head,
-                                                            Node* init, Node* stride) {
+                                                            Node* stride) {
+  Node* opaq = post_loop_head->is_canonical_loop_entry();
+  Node* init = opaq->in(1);
   Node* post_loop_entry = post_loop_head->in(LoopNode::EntryControl);
   Node* main_loop_entry = main_loop_head->in(LoopNode::EntryControl);
   IdealLoopTree* post_loop = get_loop(post_loop_head);

src/hotspot/share/opto/loopnode.hpp

@@ -938,8 +938,6 @@ class PhaseIdealLoop : public PhaseTransform {
     return ctrl;
   }
 
-  Node* cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
-
 #ifdef ASSERT
   void ensure_zero_trip_guard_proj(Node* node, bool is_main_loop);
 #endif
@@ -960,7 +958,7 @@ class PhaseIdealLoop : public PhaseTransform {
   static bool assertion_predicate_has_loop_opaque_node(IfNode* iff);
   static void get_assertion_predicates(Node* predicate, Unique_Node_List& list, bool get_opaque = false);
   void update_main_loop_assertion_predicates(Node* ctrl, CountedLoopNode* loop_head, Node* init, int stride_con);
-  void copy_assertion_predicates_to_post_loop(LoopNode* main_loop_head, CountedLoopNode* post_loop_head, Node* init,
+  void copy_assertion_predicates_to_post_loop(LoopNode* main_loop_head, CountedLoopNode* post_loop_head,
                                               Node* stride);
   void initialize_assertion_predicates_for_peeled_loop(const PredicateBlock* predicate_block, LoopNode* outer_loop_head,
                                                        int dd_outer_loop_head, Node* init, Node* stride,
@@ -1534,6 +1532,8 @@ class PhaseIdealLoop : public PhaseTransform {
   // Attempt to use a conditional move instead of a phi/branch
   Node *conditional_move( Node *n );
 
+  bool split_thru_phi_could_prevent_vectorization(Node* n, Node* n_blk);
+
   // Check for aggressive application of 'split-if' optimization,
   // using basic block level info.
   void  split_if_with_blocks     ( VectorSet &visited, Node_Stack &nstack);

src/hotspot/share/opto/loopopts.cpp

@@ -1089,6 +1089,25 @@ void PhaseIdealLoop::try_move_store_after_loop(Node* n) {
   }
 }
 
+// Split some nodes that take a counted loop phi as input at a counted
+// loop can cause vectorization of some expressions to fail
+bool PhaseIdealLoop::split_thru_phi_could_prevent_vectorization(Node* n, Node* n_blk) {
+  if (!n_blk->is_CountedLoop()) {
+    return false;
+  }
+
+  int opcode = n->Opcode();
+
+  if (opcode != Op_AndI &&
+      opcode != Op_MulI &&
+      opcode != Op_RotateRight &&
+      opcode != Op_RShiftI) {
+    return false;
+  }
+
+  return n->in(1) == n_blk->as_BaseCountedLoop()->phi();
+}
+
 //------------------------------split_if_with_blocks_pre-----------------------
 // Do the real work in a non-recursive function.  Data nodes want to be
 // cloned in the pre-order so they can feed each other nicely.
@@ -1175,6 +1194,10 @@ Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
     return n;
   }
 
+  if (split_thru_phi_could_prevent_vectorization(n, n_blk)) {
+    return n;
+  }
+
   // Check for having no control input; not pinned.  Allow
   // dominating control.
   if (n->in(0)) {