8354541: Remove Shenandoah post barrier expand loop opts

Reviewed-by: cslucas, ysr
Backport-of: 4eae9b5

Author: William Kemper

src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp

@@ -813,11 +813,6 @@ bool ShenandoahBarrierSetC2::optimize_loops(PhaseIdealLoop* phase, LoopOptsMode
     assert(UseShenandoahGC, "only for shenandoah");
     ShenandoahBarrierC2Support::pin_and_expand(phase);
     return true;
-  } else if (mode == LoopOptsShenandoahPostExpand) {
-    assert(UseShenandoahGC, "only for shenandoah");
-    visited.clear();
-    ShenandoahBarrierC2Support::optimize_after_expansion(visited, nstack, worklist, phase);
-    return true;
   }
   return false;
 }

src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.hpp

@@ -120,8 +120,8 @@ class ShenandoahBarrierSetC2 : public BarrierSetC2 {
   virtual Node* step_over_gc_barrier(Node* c) const;
   virtual bool expand_barriers(Compile* C, PhaseIterGVN& igvn) const;
   virtual bool optimize_loops(PhaseIdealLoop* phase, LoopOptsMode mode, VectorSet& visited, Node_Stack& nstack, Node_List& worklist) const;
-  virtual bool strip_mined_loops_expanded(LoopOptsMode mode) const { return mode == LoopOptsShenandoahExpand || mode == LoopOptsShenandoahPostExpand; }
-  virtual bool is_gc_specific_loop_opts_pass(LoopOptsMode mode) const { return mode == LoopOptsShenandoahExpand || mode == LoopOptsShenandoahPostExpand; }
+  virtual bool strip_mined_loops_expanded(LoopOptsMode mode) const { return mode == LoopOptsShenandoahExpand; }
+  virtual bool is_gc_specific_loop_opts_pass(LoopOptsMode mode) const { return mode == LoopOptsShenandoahExpand; }
 
   // Support for macro expanded GC barriers
   virtual void register_potential_barrier_node(Node* node) const;

src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp

@@ -52,12 +52,6 @@ bool ShenandoahBarrierC2Support::expand(Compile* C, PhaseIterGVN& igvn) {
     C->clear_major_progress();
     PhaseIdealLoop::optimize(igvn, LoopOptsShenandoahExpand);
     if (C->failing()) return false;
-
-    C->set_major_progress();
-    if (!C->optimize_loops(igvn, LoopOptsShenandoahPostExpand)) {
-      return false;
-    }
-    C->clear_major_progress();
     C->process_for_post_loop_opts_igvn(igvn);
     if (C->failing()) return false;
 
@@ -1482,236 +1476,6 @@ Node* ShenandoahBarrierC2Support::get_load_addr(PhaseIdealLoop* phase, VectorSet
 
 }
 
-void ShenandoahBarrierC2Support::move_gc_state_test_out_of_loop(IfNode* iff, PhaseIdealLoop* phase) {
-  IdealLoopTree *loop = phase->get_loop(iff);
-  Node* loop_head = loop->_head;
-  Node* entry_c = loop_head->in(LoopNode::EntryControl);
-
-  Node* bol = iff->in(1);
-  Node* cmp = bol->in(1);
-  Node* andi = cmp->in(1);
-  Node* load = andi->in(1);
-
-  assert(is_gc_state_load(load), "broken");
-  if (!phase->is_dominator(load->in(0), entry_c)) {
-    Node* mem_ctrl = nullptr;
-    Node* mem = dom_mem(load->in(MemNode::Memory), loop_head, Compile::AliasIdxRaw, mem_ctrl, phase);
-    load = load->clone();
-    load->set_req(MemNode::Memory, mem);
-    load->set_req(0, entry_c);
-    phase->register_new_node(load, entry_c);
-    andi = andi->clone();
-    andi->set_req(1, load);
-    phase->register_new_node(andi, entry_c);
-    cmp = cmp->clone();
-    cmp->set_req(1, andi);
-    phase->register_new_node(cmp, entry_c);
-    bol = bol->clone();
-    bol->set_req(1, cmp);
-    phase->register_new_node(bol, entry_c);
-
-    phase->igvn().replace_input_of(iff, 1, bol);
-  }
-}
-
-bool ShenandoahBarrierC2Support::identical_backtoback_ifs(Node* n, PhaseIdealLoop* phase) {
-  if (!n->is_If() || n->is_CountedLoopEnd()) {
-    return false;
-  }
-  Node* region = n->in(0);
-
-  if (!region->is_Region()) {
-    return false;
-  }
-  Node* dom = phase->idom(region);
-  if (!dom->is_If()) {
-    return false;
-  }
-
-  if (!is_heap_stable_test(n) || !is_heap_stable_test(dom)) {
-    return false;
-  }
-
-  IfNode* dom_if = dom->as_If();
-  Node* proj_true = dom_if->proj_out(1);
-  Node* proj_false = dom_if->proj_out(0);
-
-  for (uint i = 1; i < region->req(); i++) {
-    if (phase->is_dominator(proj_true, region->in(i))) {
-      continue;
-    }
-    if (phase->is_dominator(proj_false, region->in(i))) {
-      continue;
-    }
-    return false;
-  }
-
-  return true;
-}
-
-bool ShenandoahBarrierC2Support::merge_point_safe(Node* region) {
-  for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
-    Node* n = region->fast_out(i);
-    if (n->is_LoadStore()) {
-      // Splitting a LoadStore node through phi, causes it to lose its SCMemProj: the split if code doesn't have support
-      // for a LoadStore at the region the if is split through because that's not expected to happen (LoadStore nodes
-      // should be between barrier nodes). It does however happen with Shenandoah though because barriers can get
-      // expanded around a LoadStore node.
-      return false;
-    }
-  }
-  return true;
-}
-
-
-void ShenandoahBarrierC2Support::merge_back_to_back_tests(Node* n, PhaseIdealLoop* phase) {
-  assert(is_heap_stable_test(n), "no other tests");
-  if (identical_backtoback_ifs(n, phase)) {
-    Node* n_ctrl = n->in(0);
-    if (phase->can_split_if(n_ctrl) && merge_point_safe(n_ctrl)) {
-      IfNode* dom_if = phase->idom(n_ctrl)->as_If();
-      if (is_heap_stable_test(n)) {
-        Node* gc_state_load = n->in(1)->in(1)->in(1)->in(1);
-        assert(is_gc_state_load(gc_state_load), "broken");
-        Node* dom_gc_state_load = dom_if->in(1)->in(1)->in(1)->in(1);
-        assert(is_gc_state_load(dom_gc_state_load), "broken");
-        if (gc_state_load != dom_gc_state_load) {
-          phase->igvn().replace_node(gc_state_load, dom_gc_state_load);
-        }
-      }
-      PhiNode* bolphi = PhiNode::make_blank(n_ctrl, n->in(1));
-      Node* proj_true = dom_if->proj_out(1);
-      Node* proj_false = dom_if->proj_out(0);
-      Node* con_true = phase->igvn().makecon(TypeInt::ONE);
-      Node* con_false = phase->igvn().makecon(TypeInt::ZERO);
-
-      for (uint i = 1; i < n_ctrl->req(); i++) {
-        if (phase->is_dominator(proj_true, n_ctrl->in(i))) {
-          bolphi->init_req(i, con_true);
-        } else {
-          assert(phase->is_dominator(proj_false, n_ctrl->in(i)), "bad if");
-          bolphi->init_req(i, con_false);
-        }
-      }
-      phase->register_new_node(bolphi, n_ctrl);
-      phase->igvn().replace_input_of(n, 1, bolphi);
-      phase->do_split_if(n);
-    }
-  }
-}
-
-IfNode* ShenandoahBarrierC2Support::find_unswitching_candidate(const IdealLoopTree* loop, PhaseIdealLoop* phase) {
-  // Find first invariant test that doesn't exit the loop
-  LoopNode *head = loop->_head->as_Loop();
-  IfNode* unswitch_iff = nullptr;
-  Node* n = head->in(LoopNode::LoopBackControl);
-  int loop_has_sfpts = -1;
-  while (n != head) {
-    Node* n_dom = phase->idom(n);
-    if (n->is_Region()) {
-      if (n_dom->is_If()) {
-        IfNode* iff = n_dom->as_If();
-        if (iff->in(1)->is_Bool()) {
-          BoolNode* bol = iff->in(1)->as_Bool();
-          if (bol->in(1)->is_Cmp()) {
-            // If condition is invariant and not a loop exit,
-            // then found reason to unswitch.
-            if (is_heap_stable_test(iff) &&
-                (loop_has_sfpts == -1 || loop_has_sfpts == 0)) {
-              assert(!loop->is_loop_exit(iff), "both branches should be in the loop");
-              if (loop_has_sfpts == -1) {
-                for(uint i = 0; i < loop->_body.size(); i++) {
-                  Node *m = loop->_body[i];
-                  if (m->is_SafePoint() && !m->is_CallLeaf()) {
-                    loop_has_sfpts = 1;
-                    break;
-                  }
-                }
-                if (loop_has_sfpts == -1) {
-                  loop_has_sfpts = 0;
-                }
-              }
-              if (!loop_has_sfpts) {
-                unswitch_iff = iff;
-              }
-            }
-          }
-        }
-      }
-    }
-    n = n_dom;
-  }
-  return unswitch_iff;
-}
-
-
-void ShenandoahBarrierC2Support::optimize_after_expansion(VectorSet &visited, Node_Stack &stack, Node_List &old_new, PhaseIdealLoop* phase) {
-  Node_List heap_stable_tests;
-  stack.push(phase->C->start(), 0);
-  do {
-    Node* n = stack.node();
-    uint i = stack.index();
-
-    if (i < n->outcnt()) {
-      Node* u = n->raw_out(i);
-      stack.set_index(i+1);
-      if (!visited.test_set(u->_idx)) {
-        stack.push(u, 0);
-      }
-    } else {
-      stack.pop();
-      if (n->is_If() && is_heap_stable_test(n)) {
-        heap_stable_tests.push(n);
-      }
-    }
-  } while (stack.size() > 0);
-
-  for (uint i = 0; i < heap_stable_tests.size(); i++) {
-    Node* n = heap_stable_tests.at(i);
-    assert(is_heap_stable_test(n), "only evacuation test");
-    merge_back_to_back_tests(n, phase);
-  }
-
-  if (!phase->C->major_progress()) {
-    VectorSet seen;
-    for (uint i = 0; i < heap_stable_tests.size(); i++) {
-      Node* n = heap_stable_tests.at(i);
-      IdealLoopTree* loop = phase->get_loop(n);
-      if (loop != phase->ltree_root() &&
-          loop->_child == nullptr &&
-          !loop->_irreducible) {
-        Node* head = loop->_head;
-        if (head->is_Loop() &&
-            (!head->is_CountedLoop() || head->as_CountedLoop()->is_main_loop() || head->as_CountedLoop()->is_normal_loop()) &&
-            !seen.test_set(head->_idx)) {
-          IfNode* iff = find_unswitching_candidate(loop, phase);
-          if (iff != nullptr) {
-            Node* bol = iff->in(1);
-            if (head->as_Loop()->is_strip_mined()) {
-              head->as_Loop()->verify_strip_mined(0);
-            }
-            move_gc_state_test_out_of_loop(iff, phase);
-
-            AutoNodeBudget node_budget(phase);
-
-            if (loop->policy_unswitching(phase)) {
-              if (head->as_Loop()->is_strip_mined()) {
-                OuterStripMinedLoopNode* outer = head->as_CountedLoop()->outer_loop();
-                hide_strip_mined_loop(outer, head->as_CountedLoop(), phase);
-              }
-              phase->do_unswitching(loop, old_new);
-            } else {
-              // Not proceeding with unswitching. Move load back in
-              // the loop.
-              phase->igvn().replace_input_of(iff, 1, bol);
-            }
-          }
-        }
-      }
-    }
-  }
-}
-
 #ifdef ASSERT
 static bool has_never_branch(Node* root) {
   for (uint i = 1; i < root->req(); i++) {

src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.hpp

@@ -63,12 +63,7 @@ class ShenandoahBarrierC2Support : public AllStatic {
   static void call_lrb_stub(Node*& ctrl, Node*& val, Node* load_addr,
                             DecoratorSet decorators, PhaseIdealLoop* phase);
   static void test_in_cset(Node*& ctrl, Node*& not_cset_ctrl, Node* val, Node* raw_mem, PhaseIdealLoop* phase);
-  static void move_gc_state_test_out_of_loop(IfNode* iff, PhaseIdealLoop* phase);
-  static void merge_back_to_back_tests(Node* n, PhaseIdealLoop* phase);
-  static bool merge_point_safe(Node* region);
-  static bool identical_backtoback_ifs(Node *n, PhaseIdealLoop* phase);
   static void fix_ctrl(Node* barrier, Node* region, const MemoryGraphFixer& fixer, Unique_Node_List& uses, Unique_Node_List& uses_to_ignore, uint last, PhaseIdealLoop* phase);
-  static IfNode* find_unswitching_candidate(const IdealLoopTree *loop, PhaseIdealLoop* phase);
 
   static Node* get_load_addr(PhaseIdealLoop* phase, VectorSet& visited, Node* lrb);
 public:
@@ -80,7 +75,6 @@ class ShenandoahBarrierC2Support : public AllStatic {
 
   static bool expand(Compile* C, PhaseIterGVN& igvn);
   static void pin_and_expand(PhaseIdealLoop* phase);
-  static void optimize_after_expansion(VectorSet& visited, Node_Stack& nstack, Node_List& old_new, PhaseIdealLoop* phase);
 
 #ifdef ASSERT
   static void verify(RootNode* root);

src/hotspot/share/opto/compile.hpp

@@ -102,7 +102,6 @@ enum LoopOptsMode {
   LoopOptsNone,
   LoopOptsMaxUnroll,
   LoopOptsShenandoahExpand,
-  LoopOptsShenandoahPostExpand,
   LoopOptsSkipSplitIf,
   LoopOptsVerify
 };