8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call

rkennke · rkennke · commit 3d39f09c6cdc · 2021-11-29T16:00:09.000Z
Reviewed-by: roland, shade
diff --git a/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp b/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp
@@ -54,7 +54,6 @@ bool ShenandoahBarrierC2Support::expand(Compile* C, PhaseIterGVN& igvn) {
     PhaseIdealLoop::optimize(igvn, LoopOptsShenandoahExpand);
     if (C->failing()) return false;
     PhaseIdealLoop::verify(igvn);
-    DEBUG_ONLY(verify_raw_mem(C->root());)
     if (attempt_more_loopopts) {
       C->set_major_progress();
       if (!C->optimize_loops(igvn, LoopOptsShenandoahPostExpand)) {
@@ -964,18 +963,11 @@ void ShenandoahBarrierC2Support::test_in_cset(Node*& ctrl, Node*& not_cset_ctrl,
   phase->register_new_node(cset_bool,      old_ctrl);
 }
 
-void ShenandoahBarrierC2Support::call_lrb_stub(Node*& ctrl, Node*& val, Node* load_addr, Node*& result_mem, Node* raw_mem,
+void ShenandoahBarrierC2Support::call_lrb_stub(Node*& ctrl, Node*& val, Node* load_addr,
                                                DecoratorSet decorators, PhaseIdealLoop* phase) {
   IdealLoopTree*loop = phase->get_loop(ctrl);
   const TypePtr* obj_type = phase->igvn().type(val)->is_oopptr();
 
-  // The slow path stub consumes and produces raw memory in addition
-  // to the existing memory edges
-  Node* base = find_bottom_mem(ctrl, phase);
-  MergeMemNode* mm = MergeMemNode::make(base);
-  mm->set_memory_at(Compile::AliasIdxRaw, raw_mem);
-  phase->register_new_node(mm, ctrl);
-
   address calladdr = NULL;
   const char* name = NULL;
   bool is_strong  = ShenandoahBarrierSet::is_strong_access(decorators);
@@ -1013,16 +1005,14 @@ void ShenandoahBarrierC2Support::call_lrb_stub(Node*& ctrl, Node*& val, Node* lo
 
   call->init_req(TypeFunc::Control, ctrl);
   call->init_req(TypeFunc::I_O, phase->C->top());
-  call->init_req(TypeFunc::Memory, mm);
+  call->init_req(TypeFunc::Memory, phase->C->top());
   call->init_req(TypeFunc::FramePtr, phase->C->top());
   call->init_req(TypeFunc::ReturnAdr, phase->C->top());
   call->init_req(TypeFunc::Parms, val);
   call->init_req(TypeFunc::Parms+1, load_addr);
   phase->register_control(call, loop, ctrl);
   ctrl = new ProjNode(call, TypeFunc::Control);
   phase->register_control(ctrl, loop, call);
-  result_mem = new ProjNode(call, TypeFunc::Memory);
-  phase->register_new_node(result_mem, call);
   val = new ProjNode(call, TypeFunc::Parms);
   phase->register_new_node(val, call);
   val = new CheckCastPPNode(ctrl, val, obj_type);
@@ -1341,12 +1331,9 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     Node* ctrl = phase->get_ctrl(lrb);
     Node* val = lrb->in(ShenandoahLoadReferenceBarrierNode::ValueIn);
 
-
     Node* orig_ctrl = ctrl;
 
     Node* raw_mem = fixer.find_mem(ctrl, lrb);
-    Node* init_raw_mem = raw_mem;
-    Node* raw_mem_for_ctrl = fixer.find_mem(ctrl, NULL);
 
     IdealLoopTree *loop = phase->get_loop(ctrl);
 
@@ -1359,7 +1346,6 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     enum { _heap_stable = 1, _evac_path, _not_cset, PATH_LIMIT };
     Node* region = new RegionNode(PATH_LIMIT);
     Node* val_phi = new PhiNode(region, val->bottom_type()->is_oopptr());
-    Node* raw_mem_phi = PhiNode::make(region, raw_mem, Type::MEMORY, TypeRawPtr::BOTTOM);
 
     // Stable path.
     int flags = ShenandoahHeap::HAS_FORWARDED;
@@ -1372,7 +1358,6 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     // Heap stable case
     region->init_req(_heap_stable, heap_stable_ctrl);
     val_phi->init_req(_heap_stable, val);
-    raw_mem_phi->init_req(_heap_stable, raw_mem);
 
     // Test for in-cset, unless it's a native-LRB. Native LRBs need to return NULL
     // even for non-cset objects to prevent ressurrection of such objects.
@@ -1384,11 +1369,9 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     if (not_cset_ctrl != NULL) {
       region->init_req(_not_cset, not_cset_ctrl);
       val_phi->init_req(_not_cset, val);
-      raw_mem_phi->init_req(_not_cset, raw_mem);
     } else {
       region->del_req(_not_cset);
       val_phi->del_req(_not_cset);
-      raw_mem_phi->del_req(_not_cset);
     }
 
     // Resolve object when orig-value is in cset.
@@ -1429,15 +1412,13 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
         }
       }
     }
-    call_lrb_stub(ctrl, val, addr, result_mem, raw_mem, lrb->decorators(), phase);
+    call_lrb_stub(ctrl, val, addr, lrb->decorators(), phase);
     region->init_req(_evac_path, ctrl);
     val_phi->init_req(_evac_path, val);
-    raw_mem_phi->init_req(_evac_path, result_mem);
 
     phase->register_control(region, loop, heap_stable_iff);
     Node* out_val = val_phi;
     phase->register_new_node(val_phi, region);
-    phase->register_new_node(raw_mem_phi, region);
 
     fix_ctrl(lrb, region, fixer, uses, uses_to_ignore, last, phase);
 
@@ -1450,18 +1431,10 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     for(uint next = 0; next < uses.size(); next++ ) {
       Node *n = uses.at(next);
       assert(phase->get_ctrl(n) == ctrl, "bad control");
-      assert(n != init_raw_mem, "should leave input raw mem above the barrier");
+      assert(n != raw_mem, "should leave input raw mem above the barrier");
       phase->set_ctrl(n, region);
       follow_barrier_uses(n, ctrl, uses, phase);
     }
-
-    // The slow path call produces memory: hook the raw memory phi
-    // from the expanded load reference barrier with the rest of the graph
-    // which may require adding memory phis at every post dominated
-    // region and at enclosing loop heads. Use the memory state
-    // collected in memory_nodes to fix the memory graph. Update that
-    // memory state as we go.
-    fixer.fix_mem(ctrl, region, init_raw_mem, raw_mem_for_ctrl, raw_mem_phi, uses);
   }
   // Done expanding load-reference-barriers.
   assert(ShenandoahBarrierSetC2::bsc2()->state()->load_reference_barriers_count() == 0, "all load reference barrier nodes should have been replaced");
@@ -1902,105 +1875,6 @@ void ShenandoahBarrierC2Support::optimize_after_expansion(VectorSet &visited, No
   }
 }
 
-#ifdef ASSERT
-void ShenandoahBarrierC2Support::verify_raw_mem(RootNode* root) {
-  const bool trace = false;
-  ResourceMark rm;
-  Unique_Node_List nodes;
-  Unique_Node_List controls;
-  Unique_Node_List memories;
-
-  nodes.push(root);
-  for (uint next = 0; next < nodes.size(); next++) {
-    Node *n  = nodes.at(next);
-    if (ShenandoahBarrierSetC2::is_shenandoah_lrb_call(n)) {
-      controls.push(n);
-      if (trace) { tty->print("XXXXXX verifying"); n->dump(); }
-      for (uint next2 = 0; next2 < controls.size(); next2++) {
-        Node *m = controls.at(next2);
-        for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
-          Node* u = m->fast_out(i);
-          if (u->is_CFG() && !u->is_Root() &&
-              !(u->Opcode() == Op_CProj && u->in(0)->Opcode() == Op_NeverBranch && u->as_Proj()->_con == 1) &&
-              !(u->is_Region() && u->unique_ctrl_out()->Opcode() == Op_Halt)) {
-            if (trace) { tty->print("XXXXXX pushing control"); u->dump(); }
-            controls.push(u);
-          }
-        }
-      }
-      memories.push(n->as_Call()->proj_out(TypeFunc::Memory));
-      for (uint next2 = 0; next2 < memories.size(); next2++) {
-        Node *m = memories.at(next2);
-        assert(m->bottom_type() == Type::MEMORY, "");
-        for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
-          Node* u = m->fast_out(i);
-          if (u->bottom_type() == Type::MEMORY && (u->is_Mem() || u->is_ClearArray())) {
-            if (trace) { tty->print("XXXXXX pushing memory"); u->dump(); }
-            memories.push(u);
-          } else if (u->is_LoadStore()) {
-            if (trace) { tty->print("XXXXXX pushing memory"); u->find_out_with(Op_SCMemProj)->dump(); }
-            memories.push(u->find_out_with(Op_SCMemProj));
-          } else if (u->is_MergeMem() && u->as_MergeMem()->memory_at(Compile::AliasIdxRaw) == m) {
-            if (trace) { tty->print("XXXXXX pushing memory"); u->dump(); }
-            memories.push(u);
-          } else if (u->is_Phi()) {
-            assert(u->bottom_type() == Type::MEMORY, "");
-            if (u->adr_type() == TypeRawPtr::BOTTOM || u->adr_type() == TypePtr::BOTTOM) {
-              assert(controls.member(u->in(0)), "");
-              if (trace) { tty->print("XXXXXX pushing memory"); u->dump(); }
-              memories.push(u);
-            }
-          } else if (u->is_SafePoint() || u->is_MemBar()) {
-            for (DUIterator_Fast jmax, j = u->fast_outs(jmax); j < jmax; j++) {
-              Node* uu = u->fast_out(j);
-              if (uu->bottom_type() == Type::MEMORY) {
-                if (trace) { tty->print("XXXXXX pushing memory"); uu->dump(); }
-                memories.push(uu);
-              }
-            }
-          }
-        }
-      }
-      for (uint next2 = 0; next2 < controls.size(); next2++) {
-        Node *m = controls.at(next2);
-        if (m->is_Region()) {
-          bool all_in = true;
-          for (uint i = 1; i < m->req(); i++) {
-            if (!controls.member(m->in(i))) {
-              all_in = false;
-              break;
-            }
-          }
-          if (trace) { tty->print("XXX verifying %s", all_in ? "all in" : ""); m->dump(); }
-          bool found_phi = false;
-          for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax && !found_phi; j++) {
-            Node* u = m->fast_out(j);
-            if (u->is_Phi() && memories.member(u)) {
-              found_phi = true;
-              for (uint i = 1; i < u->req() && found_phi; i++) {
-                Node* k = u->in(i);
-                if (memories.member(k) != controls.member(m->in(i))) {
-                  found_phi = false;
-                }
-              }
-            }
-          }
-          assert(found_phi || all_in, "");
-        }
-      }
-      controls.clear();
-      memories.clear();
-    }
-    for( uint i = 0; i < n->len(); ++i ) {
-      Node *m = n->in(i);
-      if (m != NULL) {
-        nodes.push(m);
-      }
-    }
-  }
-}
-#endif
-
 ShenandoahIUBarrierNode::ShenandoahIUBarrierNode(Node* val) : Node(NULL, val) {
   ShenandoahBarrierSetC2::bsc2()->state()->add_iu_barrier(this);
 }
diff --git a/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.hpp b/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.hpp
@@ -50,7 +50,6 @@ class ShenandoahBarrierC2Support : public AllStatic {
 
   static bool verify_helper(Node* in, Node_Stack& phis, VectorSet& visited, verify_type t, bool trace, Unique_Node_List& barriers_used);
   static void report_verify_failure(const char* msg, Node* n1 = NULL, Node* n2 = NULL);
-  static void verify_raw_mem(RootNode* root);
 #endif
   static Node* dom_mem(Node* mem, Node* ctrl, int alias, Node*& mem_ctrl, PhaseIdealLoop* phase);
   static Node* no_branches(Node* c, Node* dom, bool allow_one_proj, PhaseIdealLoop* phase);
@@ -61,7 +60,7 @@ class ShenandoahBarrierC2Support : public AllStatic {
   static void test_null(Node*& ctrl, Node* val, Node*& null_ctrl, PhaseIdealLoop* phase);
   static void test_gc_state(Node*& ctrl, Node* raw_mem, Node*& heap_stable_ctrl,
                             PhaseIdealLoop* phase, int flags);
-  static void call_lrb_stub(Node*& ctrl, Node*& val, Node* load_addr, Node*& result_mem, Node* raw_mem,
+  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);
