8232539: SIGSEGV in C2 Node::unique_ctrl_out

Reviewed-by: thartmann, kvn

Author: rwestrel

src/hotspot/share/opto/ifnode.cpp

@@ -117,7 +117,7 @@ static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
   // No intervening control, like a simple Call
   Node *r = iff->in(0);
   if( !r->is_Region() ) return NULL;
-  if (r->is_Loop() && r->in(LoopNode::LoopBackControl)->is_top()) return NULL; // going away anyway
+  if (r->is_Loop()) return NULL;
   if( phi->region() != r ) return NULL;
   // No other users of the cmp/bool
   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
@@ -238,16 +238,13 @@ static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
 
   // Make a region merging constants and a region merging the rest
   uint req_c = 0;
-  Node* predicate_proj = NULL;
-  int nb_predicate_proj = 0;
   for (uint ii = 1; ii < r->req(); ii++) {
     if (phi->in(ii) == con1) {
       req_c++;
     }
     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
     if (proj != NULL) {
-      nb_predicate_proj++;
-      predicate_proj = proj;
+      return NULL;
     }
   }
 
@@ -257,24 +254,6 @@ static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
     return NULL;
   }
 
-  if (nb_predicate_proj > 1) {
-    // Can happen in case of loop unswitching and when the loop is
-    // optimized out: it's not a loop anymore so we don't care about
-    // predicates.
-    assert(!r->is_Loop(), "this must not be a loop anymore");
-    predicate_proj = NULL;
-  }
-  Node* predicate_c = NULL;
-  Node* predicate_x = NULL;
-  bool counted_loop = r->is_CountedLoop();
-  if (counted_loop) {
-    // Ignore counted loops for now because the split-if logic does not work
-    // in all the cases (for example, with strip mined loops). Also, above
-    // checks only pass for already degraded loops without a tripcount phi
-    // and these are essentially dead and will go away during igvn.
-    return NULL;
-  }
-
   Node *region_c = new RegionNode(req_c + 1);
   Node *phi_c    = con1;
   uint  len      = r->req();
@@ -283,23 +262,11 @@ static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
     if (phi->in(i) == con1) {
       region_c->init_req( i_c++, r  ->in(i) );
-      if (r->in(i) == predicate_proj)
-        predicate_c = predicate_proj;
     } else {
       region_x->init_req( i_x,   r  ->in(i) );
       phi_x   ->init_req( i_x++, phi->in(i) );
-      if (r->in(i) == predicate_proj)
-        predicate_x = predicate_proj;
     }
   }
-  if (predicate_c != NULL && (req_c > 1)) {
-    assert(predicate_x == NULL, "only one predicate entry expected");
-    predicate_c = NULL; // Do not clone predicate below merge point
-  }
-  if (predicate_x != NULL && ((len - req_c) > 2)) {
-    assert(predicate_c == NULL, "only one predicate entry expected");
-    predicate_x = NULL; // Do not clone predicate below merge point
-  }
 
   // Register the new RegionNodes but do not transform them.  Cannot
   // transform until the entire Region/Phi conglomerate has been hacked
@@ -341,20 +308,8 @@ static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
   // Make the true/false arms
   Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
   Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
-  if (predicate_c != NULL) {
-    assert(predicate_x == NULL, "only one predicate entry expected");
-    // Clone loop predicates to each path
-    iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
-    iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
-  }
   Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
   Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
-  if (predicate_x != NULL) {
-    assert(predicate_c == NULL, "only one predicate entry expected");
-    // Clone loop predicates to each path
-    iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
-    iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
-  }
 
   // Merge the TRUE paths
   Node *region_s = new RegionNode(3);