8256535: C2: randomize CCP processing order for stress testing

Add 'StressCCP' option to randomize the selection of the node to be examined in
each CCP iteration.

Reviewed-by: chagedorn, kvn, thartmann

src/hotspot/share/opto/c2_globals.hpp

@@ -50,6 +50,9 @@
   product(bool, StressIGVN, false, DIAGNOSTIC,                              \
           "Randomize worklist traversal in IGVN")                           \
                                                                             \
+  product(bool, StressCCP, false, DIAGNOSTIC,                               \
+          "Randomize worklist traversal in CCP")                            \
+                                                                            \
   product(uint, StressSeed, 0, DIAGNOSTIC,                                  \
           "Seed for randomized stress testing (if unset, a random one is "  \
           "generated). The seed is recorded in the compilation log, if "    \

src/hotspot/share/opto/compile.cpp

@@ -767,9 +767,9 @@ Compile::Compile( ciEnv* ci_env, ciMethod* target, int osr_bci,
   if (failing())  return;
   NOT_PRODUCT( verify_graph_edges(); )
 
-  // If LCM, GCM, or IGVN are randomized for stress testing, seed
+  // If any phase is randomized for stress testing, seed random number
-  // random number generation and log the seed for repeatability.
+  // generation and log the seed for repeatability.
-  if (StressLCM || StressGCM || StressIGVN) {
+  if (StressLCM || StressGCM || StressIGVN || StressCCP) {
     _stress_seed = FLAG_IS_DEFAULT(StressSeed) ?
       static_cast<uint>(Ticks::now().nanoseconds()) : StressSeed;
     if (_log != NULL) {

src/hotspot/share/opto/phaseX.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2021, 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
@@ -1714,7 +1714,12 @@ void PhaseCCP::analyze() {
   // Pull from worklist; compute new value; push changes out.
   // This loop is the meat of CCP.
   while( worklist.size() ) {
-    Node *n = worklist.pop();
+    Node* n; // Node to be examined in this iteration
+    if (StressCCP) {
+      n = worklist.remove(C->random() % worklist.size());
+    } else {
+      n = worklist.pop();
+    }
     const Type *t = n->Value(this);
     if (t != type(n)) {
       assert(ccp_type_widens(t, type(n)), "ccp type must widen");

test/hotspot/jtreg/compiler/arguments/TestStressOptions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2021, 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
@@ -23,19 +23,31 @@
 
 /*
  * @test
- * @bug 8252219
+ * @bug 8252219 8256535
  * @requires vm.compiler2.enabled
- * @summary Tests that different combinations of the options -XX:+StressIGVN and
+ * @summary Tests that different combinations of stress options and
  *          -XX:StressSeed=N are accepted.
  * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN
- *      compiler.arguments.TestStressIGVNOptions
+ *      compiler.arguments.TestStressOptions
  * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN -XX:StressSeed=42
- *      compiler.arguments.TestStressIGVNOptions
+ *      compiler.arguments.TestStressOptions
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressCCP
+ *      compiler.arguments.TestStressOptions
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressCCP -XX:StressSeed=42
+ *      compiler.arguments.TestStressOptions
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressLCM
+ *      compiler.arguments.TestStressOptions
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressLCM -XX:StressSeed=42
+ *      compiler.arguments.TestStressOptions
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressGCM
+ *      compiler.arguments.TestStressOptions
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+StressGCM -XX:StressSeed=42
+ *      compiler.arguments.TestStressOptions
  */
 
 package compiler.arguments;
 
-public class TestStressIGVNOptions {
+public class TestStressOptions {
 
     static public void main(String[] args) {
         System.out.println("Passed");

test/hotspot/jtreg/compiler/debug/TestGenerateStressSeed.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2021, 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
@@ -30,7 +30,7 @@ import jdk.test.lib.Asserts;
 
 /*
  * @test
- * @bug 8252219
+ * @bug 8252219 8256535
  * @requires vm.compiler2.enabled
  * @summary Tests that using a stress option without -XX:StressSeed=N generates
  *          and logs a random seed.
@@ -38,6 +38,7 @@ import jdk.test.lib.Asserts;
  * @run driver compiler.debug.TestGenerateStressSeed StressLCM
  * @run driver compiler.debug.TestGenerateStressSeed StressGCM
  * @run driver compiler.debug.TestGenerateStressSeed StressIGVN
+ * @run driver compiler.debug.TestGenerateStressSeed StressCCP
  */
 
 public class TestGenerateStressSeed {

test/hotspot/jtreg/compiler/debug/TestStressIGVNAndCCP.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2021, 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
@@ -29,28 +29,37 @@ import jdk.test.lib.Asserts;
 
 /*
  * @test
- * @bug 8252219
+ * @bug 8252219 8256535
  * @requires vm.debug == true & vm.compiler2.enabled
- * @summary Tests that compilations with the same seed yield the same IGVN
+ * @summary Tests that stress compilations with the same seed yield the same
- *          trace.
+ *          IGVN and CCP traces.
  * @library /test/lib /
- * @run driver compiler.debug.TestStressIGVN
+ * @run driver compiler.debug.TestStressIGVNAndCCP
  */
 
-public class TestStressIGVN {
+public class TestStressIGVNAndCCP {
 
-    static String igvnTrace(int stressSeed) throws Exception {
+    static String phaseTrace(String stressOption, String traceOption,
-        String className = TestStressIGVN.class.getName();
+                             int stressSeed) throws Exception {
+        String className = TestStressIGVNAndCCP.class.getName();
         String[] procArgs = {
             "-Xcomp", "-XX:-TieredCompilation", "-XX:-Inline",
-            "-XX:CompileOnly=" + className + "::sum", "-XX:+TraceIterativeGVN",
+            "-XX:CompileOnly=" + className + "::sum", "-XX:+" + traceOption,
-            "-XX:+StressIGVN", "-XX:StressSeed=" + stressSeed,
+            "-XX:+" + stressOption, "-XX:StressSeed=" + stressSeed,
             className, "10"};
         ProcessBuilder pb  = ProcessTools.createJavaProcessBuilder(procArgs);
         OutputAnalyzer out = new OutputAnalyzer(pb.start());
         return out.getStdout();
     }
 
+    static String igvnTrace(int stressSeed) throws Exception {
+        return phaseTrace("StressIGVN", "TraceIterativeIGVN", stressSeed);
+    }
+
+    static String ccpTrace(int stressSeed) throws Exception {
+        return phaseTrace("StressCCP", "TracePhaseCCP", stressSeed);
+    }
+
     static void sum(int n) {
         int acc = 0;
         for (int i = 0; i < n; i++) acc += i;
@@ -62,6 +71,8 @@ public class TestStressIGVN {
             for (int s = 0; s < 10; s++) {
                 Asserts.assertEQ(igvnTrace(s), igvnTrace(s),
                     "got different IGVN traces for the same seed");
+                Asserts.assertEQ(ccpTrace(s), ccpTrace(s),
+                    "got different CCP traces for the same seed");
             }
         } else if (args.length > 0) {
             sum(Integer.parseInt(args[0]));