8316105: C2: Back to back Parse Predicates from different loops but with same deopt reason are wrongly grouped together

Reviewed-by: roland, thartmann, kvn

Author: chhagedorn

src/hotspot/share/opto/predicates.cpp

@@ -77,7 +77,7 @@ Deoptimization::DeoptReason RuntimePredicate::uncommon_trap_reason(IfProjNode* i
 }
 
 bool RuntimePredicate::is_success_proj(Node* node, Deoptimization::DeoptReason deopt_reason) {
-  if (node->is_IfProj()) {
+  if (node->is_IfProj() && !node->in(0)->is_ParsePredicate()) {
     return deopt_reason == uncommon_trap_reason(node->as_IfProj());
   } else {
     return false;
@@ -108,6 +108,21 @@ ParsePredicateNode* ParsePredicateIterator::next() {
   return _parse_predicates.at(_current_index++);
 }
 
+#ifdef ASSERT
+// Check that the block has at most one Parse Predicate and that we only find Regular Predicate nodes (i.e. IfProj,
+// If, or RangeCheck nodes).
+void PredicateBlock::verify_block() {
+  Node* next = _parse_predicate.entry(); // Skip unique Parse Predicate of this block if present
+  while (next != _entry) {
+    assert(!next->is_ParsePredicate(), "can only have one Parse Predicate in a block");
+    const int opcode = next->Opcode();
+    assert(next->is_IfProj() || opcode == Op_If || opcode == Op_RangeCheck,
+           "Regular Predicates consist of an IfProj and an If or RangeCheck node");
+    next = next->in(0);
+  }
+}
+#endif // ASSERT
+
 // Walk over all Regular Predicates of this block (if any) and return the first node not belonging to the block
 // anymore (i.e. entry to the first Regular Predicate in this block if any or `regular_predicate_proj` otherwise).
 Node* PredicateBlock::skip_regular_predicates(Node* regular_predicate_proj, Deoptimization::DeoptReason deopt_reason) {

src/hotspot/share/opto/predicates.hpp

@@ -270,11 +270,14 @@ class PredicateBlock : public StackObj {
   Node* _entry;
 
   static Node* skip_regular_predicates(Node* regular_predicate_proj, Deoptimization::DeoptReason deopt_reason);
+  DEBUG_ONLY(void verify_block();)
 
  public:
   PredicateBlock(Node* predicate_proj, Deoptimization::DeoptReason deopt_reason)
       : _parse_predicate(predicate_proj, deopt_reason),
-        _entry(skip_regular_predicates(_parse_predicate.entry(), deopt_reason)) {}
+        _entry(skip_regular_predicates(_parse_predicate.entry(), deopt_reason)) {
+    DEBUG_ONLY(verify_block();)
+  }
 
   // Returns the control input node into this Regular Predicate block. This is either:
   // - The control input to the first If node in the block representing a Runtime Predicate if there is at least one

test/hotspot/jtreg/compiler/predicates/TestBackToBackParsePredicates.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2023, 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 8316105
+ * @library /test/lib
+ * @summary Test that back to back Parse Predicates with same deopt reason are not grouped together
+ * @run main/othervm -Xbatch compiler.predicates.TestBackToBackParsePredicates
+ */
+
+package compiler.predicates;
+
+import jdk.test.lib.Asserts;
+
+public class TestBackToBackParsePredicates {
+    static long lFld;
+
+    public static void main(String[] strArr2) {
+        for (int i = -350; i <= 0; i++) {
+            lFld = 30;
+            test(i);
+            check();
+        }
+        lFld = 30;
+        test(1);
+        check();
+    }
+
+    // Inlined
+    static void foo() {
+        for (int i12 = 1; i12 < 5; i12++) { // Loop A
+            lFld += 1; // StoreL
+        }
+    }
+
+    static void test(int x) {
+        foo();
+
+        // After fully unrolling loop A and after next round of IGVN:
+        // We wrongly treat two back to back Loop Limit Check Parse Predicates as single Predicate Block. We therefore
+        // keep the Loop Parse Predicate of loop A:
+        //
+        // Loop Parse Predicate (of A)
+        // Loop Limit Check Parse Predicate (of A)  |
+        //    -> StoreL of lFld pinned here         | Wrongly treated as single Predicate Block
+        // Loop Limit Check Parse Predicate (of B)  |
+        for (int i = 7; i < 212; i++) { // Loop B
+            for (int j = 1; j < 80; j++) {
+                switch (x % 8) {
+                    case 0:
+                    case 2:
+                        break;
+                    case 6:
+                    case 7:
+                }
+            }
+        }
+    }
+
+    static void check() {
+        Asserts.assertEQ(34L, lFld);
+    }
+}