8187822: C2 conditonal move optimization might create broken graph

Reviewed-by: kvn

src/share/vm/opto/loopopts.cpp

 /*
- * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2017, 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
@@ -309,6 +309,7 @@ Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
       }
       return NULL;
     }
+    assert(m->is_Phi() || is_dominator(get_ctrl(m), n_ctrl), "m has strange control");
   }
 
   return n_ctrl;
@@ -609,6 +610,7 @@ Node *PhaseIdealLoop::conditional_move( Node *region ) {
   // Now replace all Phis with CMOV's
   Node *cmov_ctrl = iff->in(0);
   uint flip = (lp->Opcode() == Op_IfTrue);
+  Node_List wq;
   while (1) {
     PhiNode* phi = NULL;
     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
@@ -623,17 +625,21 @@ Node *PhaseIdealLoop::conditional_move( Node *region ) {
     if (PrintOpto && VerifyLoopOptimizations) tty->print_cr("CMOV");
 #endif
     // Move speculative ops
-    for (uint j = 1; j < region->req(); j++) {
-      Node *proj = region->in(j);
-      Node *inp = phi->in(j);
-      if (get_ctrl(inp) == proj) { // Found local op
+    wq.push(phi);
+    while (wq.size() > 0) {
+      Node *n = wq.pop();
+      for (uint j = 1; j < n->req(); j++) {
+        Node* m = n->in(j);
+        if (m != NULL && !is_dominator(get_ctrl(m), cmov_ctrl)) {
 #ifndef PRODUCT
-        if (PrintOpto && VerifyLoopOptimizations) {
-          tty->print("  speculate: ");
-          inp->dump();
-        }
+          if (PrintOpto && VerifyLoopOptimizations) {
+            tty->print("  speculate: ");
+            m->dump();
+          }
 #endif
-        set_ctrl(inp, cmov_ctrl);
+          set_ctrl(m, cmov_ctrl);
+          wq.push(m);
+        }
       }
     }
     Node *cmov = CMoveNode::make( C, cmov_ctrl, iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi) );

test/compiler/loopopts/TestCMovSplitThruPhi.java

+/*
+ * Copyright (c) 2017, Red Hat, Inc. 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 8187822
+ * @summary C2 conditonal move optimization might create broken graph
+ * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:CompileCommand=dontinline,TestCMovSplitThruPhi::not_inlined -XX:CompileOnly=TestCMovSplitThruPhi::test -XX:-LoopUnswitching TestCMovSplitThruPhi
+ *
+ */
+
+public class TestCMovSplitThruPhi {
+    static int f;
+
+    static int test(boolean flag1, boolean flag2, boolean flag3, boolean flag4) {
+        int v3 = 0;
+        if (flag4) {
+            for (int i = 0; i < 10; i++) {
+                int v1 = 0;
+                if (flag1) {
+                    v1 = not_inlined();
+                }
+                // AddI below will be candidate for split through Phi
+                int v2 = v1;
+                if (flag2) {
+                    v2 = f + v1;
+                }
+                // test above will be converted to CMovI
+                if (flag3) {
+                    v3 = v2 * 2;
+                    break;
+                }
+            }
+        }
+        return v3;
+    }
+
+    private static int not_inlined() {
+        return 0;
+    }
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 20000; i++) {
+            test((i % 2) == 0, (i % 2) == 0, (i % 100) == 1, (i % 1000) == 1);
+        }
+    }
+}