8078426: mb/jvm/compiler/InterfaceCalls/testAC2 - assert(predicate_proj == 0L) failed: only one predicate entry expected

Split if finds predicates on several incoming paths when unswitched's loops are optimized out

Reviewed-by: kvn

hotspot/src/share/vm/opto/ifnode.cpp

@@ -234,16 +234,24 @@ 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) {
-      assert(predicate_proj == NULL, "only one predicate entry expected");
+      nb_predicate_proj++;
       predicate_proj = proj;
     }
   }
+  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();

hotspot/src/share/vm/opto/loopPredicate.cpp

@@ -89,7 +89,7 @@ void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred)
 //
 // We will create a region to guard the uct call if there is no one there.
 // The true projecttion (if_cont) of the new_iff is returned.
-// This code is also used to clone predicates to clonned loops.
+// This code is also used to clone predicates to cloned loops.
 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
                                                       Deoptimization::DeoptReason reason) {
   assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");

hotspot/test/compiler/loopopts/TestSplitIfUnswitchedLoopsEliminated.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+/**
+ * @test
+ * @bug 8078426
+ * @summary split if finds predicates on several incoming paths when unswitched's loops are optimized out
+ * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-UseCompressedOops TestSplitIfUnswitchedLoopsEliminated
+ *
+ */
+
+
+public class TestSplitIfUnswitchedLoopsEliminated {
+
+    static class A {
+        int f;
+    }
+
+    static A aa = new A();
+    static A aaa = new A();
+
+    static int test_helper(int stop, boolean unswitch) {
+        A a = null;
+        for (int i = 3; i < 10; i++) {
+            if (unswitch) {
+                a = null;
+            } else {
+                a = aa;
+                int v = a.f;
+            }
+        }
+        if (stop != 4) {
+            a = aaa;
+        }
+        if (a != null) {
+            return a.f;
+        }
+        return 0;
+    }
+
+    static int test(boolean unswitch) {
+        int stop = 1;
+        for (; stop < 3; stop *= 4) {
+        }
+        return test_helper(stop, unswitch);
+    }
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 20000; i++) {
+            test_helper(10, i%2 == 0);
+            test(i%2 == 0);
+        }
+    }
+}