8347449: C2: UseLoopPredicate off should also turn UseProfiledLoopPredicate off

Reviewed-by: chagedorn, epeter

Author: mhaessig

src/hotspot/share/opto/c2_globals.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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
@@ -238,7 +238,7 @@
           "Force counted loops to keep a safepoint")                        \
                                                                             \
   product(bool, UseLoopPredicate, true,                                     \
-          "Generate a predicate to select fast/slow loop versions")         \
+          "Move checks with uncommon trap out of loops.")                   \
                                                                             \
   develop(bool, TraceLoopPredicate, false,                                  \
           "Trace generation of loop predicates")                            \
@@ -785,7 +785,9 @@
           range(0, max_juint)                                               \
                                                                             \
   product(bool, UseProfiledLoopPredicate, true,                             \
-          "Move predicates out of loops based on profiling data")           \
+          "Move checks with an uncommon trap out of loops based on "        \
+          "profiling data. "                                                \
+          "Requires UseLoopPredicate to be turned on (default).")           \
                                                                             \
   develop(uintx, StressLongCountedLoop, 0,                                  \
           "if > 0, convert int counted loops to long counted loops"         \

src/hotspot/share/opto/graphKit.cpp

@@ -4037,9 +4037,9 @@ void GraphKit::add_parse_predicate(Deoptimization::DeoptReason reason, const int
 void GraphKit::add_parse_predicates(int nargs) {
   if (UseLoopPredicate) {
     add_parse_predicate(Deoptimization::Reason_predicate, nargs);
-  }
-  if (UseProfiledLoopPredicate) {
-    add_parse_predicate(Deoptimization::Reason_profile_predicate, nargs);
+    if (UseProfiledLoopPredicate) {
+      add_parse_predicate(Deoptimization::Reason_profile_predicate, nargs);
+    }
   }
   add_parse_predicate(Deoptimization::Reason_auto_vectorization_check, nargs);
   // Loop Limit Check Predicate should be near the loop.

src/hotspot/share/opto/idealKit.cpp

@@ -163,14 +163,12 @@ void IdealKit::end_if() {
 // onto the stack.
 void IdealKit::loop(GraphKit* gkit, int nargs, IdealVariable& iv, Node* init, BoolTest::mask relop, Node* limit, float prob, float cnt) {
   assert((state() & (BlockS|LoopS|IfThenS|ElseS)), "bad state for new loop");
-  if (UseLoopPredicate) {
-    // Sync IdealKit and graphKit.
-    gkit->sync_kit(*this);
-    // Add Parse Predicates.
-    gkit->add_parse_predicates(nargs);
-    // Update IdealKit memory.
-    sync_kit(gkit);
-  }
+  // Sync IdealKit and graphKit.
+  gkit->sync_kit(*this);
+  // Add Parse Predicates.
+  gkit->add_parse_predicates(nargs);
+  // Update IdealKit memory.
+  sync_kit(gkit);
   set(iv, init);
   Node* head = make_label(1);
   bind(head);

src/hotspot/share/opto/loopnode.cpp

@@ -1087,9 +1087,9 @@ bool PhaseIdealLoop::create_loop_nest(IdealLoopTree* loop, Node_List &old_new) {
 
     if (UseLoopPredicate) {
       add_parse_predicate(Deoptimization::Reason_predicate, inner_head, outer_ilt, cloned_sfpt);
-    }
-    if (UseProfiledLoopPredicate) {
-      add_parse_predicate(Deoptimization::Reason_profile_predicate, inner_head, outer_ilt, cloned_sfpt);
+      if (UseProfiledLoopPredicate) {
+        add_parse_predicate(Deoptimization::Reason_profile_predicate, inner_head, outer_ilt, cloned_sfpt);
+      }
     }
 
     // We only want to use the auto-vectorization check as a trap once per bci. And
@@ -4298,11 +4298,13 @@ void IdealLoopTree::dump_head() {
   if (predicates.loop_limit_check_predicate_block()->is_non_empty()) {
     tty->print(" limit_check");
   }
-  if (UseProfiledLoopPredicate && predicates.profiled_loop_predicate_block()->is_non_empty()) {
-    tty->print(" profile_predicated");
-  }
-  if (UseLoopPredicate && predicates.loop_predicate_block()->is_non_empty()) {
-    tty->print(" predicated");
+  if (UseLoopPredicate) {
+    if (UseProfiledLoopPredicate && predicates.profiled_loop_predicate_block()->is_non_empty()) {
+      tty->print(" profile_predicated");
+    }
+    if (predicates.loop_predicate_block()->is_non_empty()) {
+      tty->print(" predicated");
+    }
   }
   if (_head->is_CountedLoop()) {
     CountedLoopNode *cl = _head->as_CountedLoop();

src/hotspot/share/runtime/arguments.cpp

@@ -3797,6 +3797,13 @@ jint Arguments::apply_ergo() {
   }
 #endif // COMPILER2_OR_JVMCI
 
+#ifdef COMPILER2
+  if (!FLAG_IS_DEFAULT(UseLoopPredicate) && !UseLoopPredicate && UseProfiledLoopPredicate) {
+    warning("Disabling UseProfiledLoopPredicate since UseLoopPredicate is turned off.");
+    FLAG_SET_ERGO(UseProfiledLoopPredicate, false);
+  }
+#endif // COMPILER2
+
   if (log_is_enabled(Info, perf, class, link)) {
     if (!UsePerfData) {
       warning("Disabling -Xlog:perf+class+link since UsePerfData is turned off.");

test/hotspot/jtreg/compiler/lib/ir_framework/IRNode.java

@@ -1539,6 +1539,21 @@ public class IRNode {
                                                                        CompilePhase.BEFORE_MATCHING));
     }
 
+    public static final String LOOP_PARSE_PREDICATE = PREFIX + "LOOP_PARSE_PREDICATE" + POSTFIX;
+    static {
+        parsePredicateNodes(LOOP_PARSE_PREDICATE, "Loop");
+    }
+
+    public static final String LOOP_LIMIT_CHECK_PARSE_PREDICATE = PREFIX + "LOOP_LIMIT_CHECK_PARSE_PREDICATE" + POSTFIX;
+    static {
+        parsePredicateNodes(LOOP_LIMIT_CHECK_PARSE_PREDICATE, "Loop Limit Check");
+    }
+
+    public static final String PROFILED_LOOP_PARSE_PREDICATE = PREFIX + "PROFILED_LOOP_PARSE_PREDICATE" + POSTFIX;
+    static {
+        parsePredicateNodes(PROFILED_LOOP_PARSE_PREDICATE, "Profiled Loop");
+    }
+
     public static final String PREDICATE_TRAP = PREFIX + "PREDICATE_TRAP" + POSTFIX;
     static {
         trapNodes(PREDICATE_TRAP, "predicate");
@@ -2761,6 +2776,13 @@ private static void trapNodes(String irNodePlaceholder, String trapReason) {
         beforeMatching(irNodePlaceholder, regex);
     }
 
+    private static void parsePredicateNodes(String irNodePlaceholder, String label) {
+        String regex = START + "ParsePredicate" + MID + "#" + label + "[ ]*!jvms:" + END;
+        IR_NODE_MAPPINGS.put(irNodePlaceholder, new SinglePhaseRangeEntry(CompilePhase.AFTER_PARSING, regex,
+                                                                          CompilePhase.AFTER_PARSING,
+                                                                          CompilePhase.PHASEIDEALLOOP_ITERATIONS));
+    }
+
     private static void loadOfNodes(String irNodePlaceholder, String irNodeRegex) {
         String regex = START + irNodeRegex + MID + "@\\S*" + IS_REPLACED + LOAD_OF_CLASS_POSTFIX;
         beforeMatching(irNodePlaceholder, regex);

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

@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2025, 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.
+ *
+ */
+
+package compiler.predicates;
+
+import compiler.lib.ir_framework.*;
+import jdk.test.lib.Asserts;
+
+/*
+ * @test
+ * @bug 8347449
+ * @summary Test that profiled loop predicates are turned off if loop predicates are turned off
+ * @library /test/lib /
+ * @run driver compiler.predicates.TestDisabledLoopPredicates
+ */
+
+public class TestDisabledLoopPredicates {
+    static final int SIZE = 100;
+    static final int MIN = 3;
+
+    public static void main(String[] args) {
+        TestFramework.runWithFlags("-XX:+UseLoopPredicate",
+                                   "-XX:+UseProfiledLoopPredicate");
+        TestFramework.runWithFlags("-XX:-UseLoopPredicate");
+        TestFramework.runWithFlags("-XX:-UseProfiledLoopPredicate");
+    }
+
+    @Run(test = "test")
+    private static void check() {
+        int res = test(true);
+        Asserts.assertEQ(res, ((SIZE - 1) * SIZE - MIN * (MIN + 1)) / 2);
+    }
+
+    @DontInline
+    private static void blackhole(int i) {
+    }
+
+    @DontInline
+    private static int[] getArr() {
+        int[] arr = new int[SIZE];
+        for (int i = 0; i < SIZE; i++) {
+            arr[i] = i;
+        }
+
+        return arr;
+    }
+
+    @Test
+    @IR(counts = { IRNode.LOOP_PARSE_PREDICATE, "1",
+                   IRNode.PROFILED_LOOP_PARSE_PREDICATE, "1" },
+        applyIfAnd = { "UseLoopPredicate", "true",
+                       "UseProfiledLoopPredicate", "true" })
+    @IR(failOn = { IRNode.LOOP_PARSE_PREDICATE,
+                   IRNode.PROFILED_LOOP_PARSE_PREDICATE },
+        applyIf = { "UseLoopPredicate", "false" })
+    @IR(counts = { IRNode.LOOP_PARSE_PREDICATE, "1" },
+        failOn = { IRNode.PROFILED_LOOP_PARSE_PREDICATE },
+        applyIfAnd = { "UseLoopPredicate", "true",
+                       "UseProfiledLoopPredicate", "false" })
+    public static int test(boolean cond) {
+        int[] arr = getArr();
+        int sum = 0;
+        for (int i = 0; i < arr.length; i++) {
+            if (cond) {
+                if (arr[i] > MIN) {
+                    sum += arr[i];
+                }
+            }
+            blackhole(arr[i]);
+        }
+
+        return sum;
+    }
+}