8280799: С2: assert(false) failed: cyclic dependency prevents range c…

…heck elimination

Reviewed-by: thartmann, kvn

src/hotspot/share/opto/loopnode.cpp

@@ -5725,38 +5725,45 @@ void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
   }
   assert(early == legal || legal != C->root(), "bad dominance of inputs");
 
+  if (least != early) {
+    // Move the node above predicates as far up as possible so a
+    // following pass of loop predication doesn't hoist a predicate
+    // that depends on it above that node.
+    Node* new_ctrl = least;
+    for (;;) {
+      if (!new_ctrl->is_Proj()) {
+        break;
+      }
+      CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
+      if (call == NULL) {
+        break;
+      }
+      int req = call->uncommon_trap_request();
+      Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
+      if (trap_reason != Deoptimization::Reason_loop_limit_check &&
+          trap_reason != Deoptimization::Reason_predicate &&
+          trap_reason != Deoptimization::Reason_profile_predicate) {
+        break;
+      }
+      Node* c = new_ctrl->in(0)->in(0);
+      if (is_dominator(c, early) && c != early) {
+        break;
+      }
+      new_ctrl = c;
+    }
+    least = new_ctrl;
+  }
   // Try not to place code on a loop entry projection
   // which can inhibit range check elimination.
   if (least != early) {
     Node* ctrl_out = least->unique_ctrl_out();
     if (ctrl_out && ctrl_out->is_Loop() &&
-        least == ctrl_out->in(LoopNode::EntryControl)) {
-      // Move the node above predicates as far up as possible so a
-      // following pass of loop predication doesn't hoist a predicate
-      // that depends on it above that node.
-      Node* new_ctrl = least;
-      for (;;) {
-        if (!new_ctrl->is_Proj()) {
-          break;
-        }
-        CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
-        if (call == NULL) {
-          break;
-        }
-        int req = call->uncommon_trap_request();
-        Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
-        if (trap_reason != Deoptimization::Reason_loop_limit_check &&
-            trap_reason != Deoptimization::Reason_predicate &&
-            trap_reason != Deoptimization::Reason_profile_predicate) {
-          break;
-        }
-        Node* c = new_ctrl->in(0)->in(0);
-        if (is_dominator(c, early) && c != early) {
-          break;
-        }
-        new_ctrl = c;
+        least == ctrl_out->in(LoopNode::EntryControl) &&
+        (ctrl_out->is_CountedLoop() || ctrl_out->is_OuterStripMinedLoop())) {
+      Node* least_dom = idom(least);
+      if (get_loop(least_dom)->is_member(get_loop(least))) {
+        least = least_dom;
       }
-      least = new_ctrl;
     }
   }
 

src/hotspot/share/opto/split_if.cpp

@@ -201,6 +201,24 @@ bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
       return true;
     }
   }
+  if (n->Opcode() == Op_OpaqueLoopStride || n->Opcode() == Op_OpaqueLoopInit) {
+    Unique_Node_List wq;
+    wq.push(n);
+    for (uint i = 0; i < wq.size(); i++) {
+      Node* m = wq.at(i);
+      if (m->is_If()) {
+        assert(skeleton_predicate_has_opaque(m->as_If()), "opaque node not reachable from if?");
+        Node* bol = clone_skeleton_predicate_bool(m, NULL, NULL, m->in(0));
+        _igvn.replace_input_of(m, 1, bol);
+      } else {
+        assert(!m->is_CFG(), "not CFG expected");
+        for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
+          Node* u = m->fast_out(j);
+          wq.push(u);
+        }
+      }
+    }
+  }
 
   // See if splitting-up a Store.  Any anti-dep loads must go up as
   // well.  An anti-dep load might be in the wrong block, because in

test/hotspot/jtreg/compiler/loopopts/TestPredicateInputBelowLoopPredicate.java

@@ -0,0 +1,268 @@
+/*
+ * Copyright (c) 2022, 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 8280799
+ * @summary С2: assert(false) failed: cyclic dependency prevents range check elimination
+ * @run main/othervm -XX:-BackgroundCompilation -XX:-UseCountedLoopSafepoints TestPredicateInputBelowLoopPredicate
+ */
+
+public class TestPredicateInputBelowLoopPredicate {
+    private static final Object object = new Object();
+    private static int fieldStop = 100;
+    private static int[] array = new int[200];
+    private static int[] array2 = new int[200];
+    private static int fieldStart = 0;
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 20_000; i++) {
+            test(true);
+            test(false);
+        }
+    }
+
+    private static void test(boolean flag) {
+        if (array == null) {
+        }
+        int start = fieldStart;
+        int i = start;
+        for(;;) {
+            int j;
+            for (j = -10; j < 0; j++) {
+            }
+            int stop = fieldStop;
+             // bound check becomes candidate for predication once
+             // loop above is optimized out
+            array[stop - i + j] = 0;
+
+            // A bunch of stuff to grow loop body size and prevent peeling:
+            array2[0] = 0;
+            array2[1] = 0;
+            array2[2] = 0;
+            array2[3] = 0;
+            array2[4] = 0;
+            array2[5] = 0;
+            array2[6] = 0;
+            array2[7] = 0;
+            array2[8] = 0;
+            array2[9] = 0;
+            array2[10] = 0;
+            array2[11] = 0;
+            array2[12] = 0;
+            array2[13] = 0;
+            array2[14] = 0;
+            array2[15] = 0;
+            array2[16] = 0;
+            array2[17] = 0;
+            array2[18] = 0;
+            array2[19] = 0;
+            array2[20] = 0;
+            array2[21] = 0;
+            array2[22] = 0;
+            array2[23] = 0;
+            array2[24] = 0;
+            array2[25] = 0;
+            array2[26] = 0;
+            array2[27] = 0;
+            array2[28] = 0;
+            array2[29] = 0;
+            array2[30] = 0;
+            array2[31] = 0;
+            array2[32] = 0;
+            array2[33] = 0;
+            array2[34] = 0;
+            array2[35] = 0;
+            array2[36] = 0;
+            array2[37] = 0;
+            array2[38] = 0;
+            array2[39] = 0;
+            array2[40] = 0;
+            array2[41] = 0;
+            array2[42] = 0;
+            array2[43] = 0;
+            array2[44] = 0;
+            array2[45] = 0;
+            array2[46] = 0;
+            array2[47] = 0;
+            array2[48] = 0;
+            array2[49] = 0;
+            array2[50] = 0;
+            array2[51] = 0;
+            array2[52] = 0;
+            array2[53] = 0;
+            array2[54] = 0;
+            array2[55] = 0;
+            array2[56] = 0;
+            array2[57] = 0;
+            array2[58] = 0;
+            array2[59] = 0;
+            array2[60] = 0;
+            array2[61] = 0;
+            array2[62] = 0;
+            array2[63] = 0;
+            array2[64] = 0;
+            array2[65] = 0;
+            array2[66] = 0;
+            array2[67] = 0;
+            array2[68] = 0;
+            array2[69] = 0;
+            array2[70] = 0;
+            array2[71] = 0;
+            array2[72] = 0;
+            array2[73] = 0;
+            array2[74] = 0;
+            array2[75] = 0;
+            array2[76] = 0;
+            array2[77] = 0;
+            array2[78] = 0;
+            array2[79] = 0;
+            array2[80] = 0;
+            array2[81] = 0;
+            array2[82] = 0;
+            array2[83] = 0;
+            array2[84] = 0;
+            array2[85] = 0;
+            array2[86] = 0;
+            array2[87] = 0;
+            array2[88] = 0;
+            array2[89] = 0;
+            array2[90] = 0;
+            array2[91] = 0;
+            array2[92] = 0;
+            array2[93] = 0;
+            array2[94] = 0;
+            array2[95] = 0;
+            array2[96] = 0;
+            array2[97] = 0;
+            array2[98] = 0;
+            array2[99] = 0;
+
+            array2[100] = 0;
+            array2[101] = 0;
+            array2[102] = 0;
+            array2[103] = 0;
+            array2[104] = 0;
+            array2[105] = 0;
+            array2[106] = 0;
+            array2[107] = 0;
+            array2[108] = 0;
+            array2[109] = 0;
+            array2[110] = 0;
+            array2[111] = 0;
+            array2[112] = 0;
+            array2[113] = 0;
+            array2[114] = 0;
+            array2[115] = 0;
+            array2[116] = 0;
+            array2[117] = 0;
+            array2[118] = 0;
+            array2[119] = 0;
+            array2[120] = 0;
+            array2[121] = 0;
+            array2[122] = 0;
+            array2[123] = 0;
+            array2[124] = 0;
+            array2[125] = 0;
+            array2[126] = 0;
+            array2[127] = 0;
+            array2[128] = 0;
+            array2[129] = 0;
+            array2[130] = 0;
+            array2[131] = 0;
+            array2[132] = 0;
+            array2[133] = 0;
+            array2[134] = 0;
+            array2[135] = 0;
+            array2[136] = 0;
+            array2[137] = 0;
+            array2[138] = 0;
+            array2[139] = 0;
+            array2[140] = 0;
+            array2[141] = 0;
+            array2[142] = 0;
+            array2[143] = 0;
+            array2[144] = 0;
+            array2[145] = 0;
+            array2[146] = 0;
+            array2[147] = 0;
+            array2[148] = 0;
+            array2[149] = 0;
+            array2[150] = 0;
+            array2[151] = 0;
+            array2[152] = 0;
+            array2[153] = 0;
+            array2[154] = 0;
+            array2[155] = 0;
+            array2[156] = 0;
+            array2[157] = 0;
+            array2[158] = 0;
+            array2[159] = 0;
+            array2[160] = 0;
+            array2[161] = 0;
+            array2[162] = 0;
+            array2[163] = 0;
+            array2[164] = 0;
+            array2[165] = 0;
+            array2[166] = 0;
+            array2[167] = 0;
+            array2[168] = 0;
+            array2[169] = 0;
+            array2[170] = 0;
+            array2[171] = 0;
+            array2[172] = 0;
+            array2[173] = 0;
+            array2[174] = 0;
+            array2[175] = 0;
+            array2[176] = 0;
+            array2[177] = 0;
+            array2[178] = 0;
+            array2[179] = 0;
+            array2[180] = 0;
+            array2[181] = 0;
+            array2[182] = 0;
+            array2[183] = 0;
+            array2[184] = 0;
+            array2[185] = 0;
+            array2[186] = 0;
+            array2[187] = 0;
+            array2[188] = 0;
+            array2[189] = 0;
+            array2[190] = 0;
+            array2[191] = 0;
+            array2[192] = 0;
+            array2[193] = 0;
+            array2[194] = 0;
+            array2[195] = 0;
+            array2[196] = 0;
+            array2[197] = 0;
+            array2[198] = 0;
+            array2[199] = 0;
+            i++;
+
+            if (i == stop) { // requires a loop limit predicate
+                break;
+            }
+        }
+    }
+}