8253765: C2: Control randomization in StressLCM and StressGCM

Use the compilation-local seed in 'StressLCM' and 'StressGCM' rather than the
global one. As a consequence, these options use by default a fresh seed in every
compilation, unless 'StressSeed=N' is specified, in which case they behave
deterministically. Annotate tests that use 'StressLCM' and 'StressGCM' with the
'stress' and 'randomness' keys to reflect this change in default behavior.

Reviewed-by: kvn, thartmann

Author: robcasloz

src/hotspot/share/opto/c2_globals.hpp

@@ -53,8 +53,8 @@
           "Randomize worklist traversal in IGVN")                           \
                                                                             \
   product(uint, StressSeed, 0, DIAGNOSTIC,                                  \
-          "Seed for IGVN stress testing (if unset, a random one is "        \
-          "generated")                                                      \
+          "Seed for randomized stress testing (if unset, a random one is "  \
+          "generated)")                                                     \
           range(0, max_juint)                                               \
                                                                             \
   develop(bool, StressMethodHandleLinkerInlining, false,                    \

src/hotspot/share/opto/compile.cpp

@@ -729,9 +729,9 @@ Compile::Compile( ciEnv* ci_env, ciMethod* target, int osr_bci,
   if (failing())  return;
   NOT_PRODUCT( verify_graph_edges(); )
 
-  // If IGVN is randomized for stress testing, seed random number
-  // generation and log the seed for repeatability.
-  if (StressIGVN) {
+  // If LCM, GCM, or IGVN are randomized for stress testing, seed
+  // random number generation and log the seed for repeatability.
+  if (StressLCM || StressGCM || StressIGVN) {
     _stress_seed = FLAG_IS_DEFAULT(StressSeed) ?
       static_cast<uint>(Ticks::now().nanoseconds()) : StressSeed;
     if (_log != NULL) {
@@ -4489,7 +4489,7 @@ int Compile::random() {
 #define RANDOMIZED_DOMAIN_MASK ((1 << (RANDOMIZED_DOMAIN_POW + 1)) - 1)
 bool Compile::randomized_select(int count) {
   assert(count > 0, "only positive");
-  return (os::random() & RANDOMIZED_DOMAIN_MASK) < (RANDOMIZED_DOMAIN / count);
+  return (random() & RANDOMIZED_DOMAIN_MASK) < (RANDOMIZED_DOMAIN / count);
 }
 
 CloneMap&     Compile::clone_map()                 { return _clone_map; }

src/hotspot/share/opto/compile.hpp

@@ -1140,7 +1140,7 @@ class Compile : public Phase {
 
   // Auxiliary methods for randomized fuzzing/stressing
   int random();
-  static bool randomized_select(int count);
+  bool randomized_select(int count);
 
   // supporting clone_map
   CloneMap&     clone_map();

src/hotspot/share/opto/gcm.cpp

@@ -1198,7 +1198,7 @@ Block* PhaseCFG::hoist_to_cheaper_block(Block* LCA, Block* early, Node* self) {
 #endif
     cand_cnt++;
     if (LCA_freq < least_freq              || // Better Frequency
-        (StressGCM && Compile::randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode
+        (StressGCM && C->randomized_select(cand_cnt)) || // Should be randomly accepted in stress mode
          (!StressGCM                    &&    // Otherwise, choose with latency
           !in_latency                   &&    // No block containing latency
           LCA_freq < least_freq * delta &&    // No worse frequency

src/hotspot/share/opto/lcm.cpp

@@ -632,7 +632,7 @@ Node* PhaseCFG::select(
     cand_cnt++;
     if (choice < n_choice ||
         (choice == n_choice &&
-         ((StressLCM && Compile::randomized_select(cand_cnt)) ||
+         ((StressLCM && C->randomized_select(cand_cnt)) ||
           (!StressLCM &&
            (latency < n_latency ||
             (latency == n_latency &&

test/hotspot/jtreg/compiler/arraycopy/TestCloneAccessStressGCM.java

@@ -23,6 +23,7 @@
 
 /*
  * @test
+ * @key stress randomness
  * @bug 8235332 8248226
  * @summary Test cloning with more than 8 (=ArrayCopyLoadStoreMaxElem) fields with StressGCM
  * @library /

test/hotspot/jtreg/compiler/arraycopy/TestInitializingACLoadWithBadMem.java

@@ -23,6 +23,7 @@
 
 /**
  * @test
+ * @key stress randomness
  * @bug 8182036
  * @summary Load from initializing arraycopy uses wrong memory state
  *

test/hotspot/jtreg/compiler/arraycopy/TestLoadBypassACWithWrongMem.java

@@ -23,6 +23,7 @@
 
 /**
  * @test
+ * @key stress randomness
  * @bug 8181742
  * @summary Loads that bypass arraycopy ends up with wrong memory state
  *

test/hotspot/jtreg/compiler/controldependency/TestEliminatedCastPPAtPhi.java

@@ -23,6 +23,7 @@
 
 /**
  * @test
+ * @key stress randomness
  * @bug 8139771
  * @summary Eliminating CastPP nodes at Phis when they all come from a unique input may cause crash
  * @requires vm.gc=="Serial" | vm.gc=="Parallel"

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

@@ -32,10 +32,12 @@
  * @test
  * @bug 8252219
  * @requires vm.compiler2.enabled
- * @summary Tests that using -XX:+StressIGVN without -XX:StressSeed=N generates
+ * @summary Tests that using a stress option without -XX:StressSeed=N generates
  *          and logs a random seed.
  * @library /test/lib /
- * @run driver compiler.debug.TestGenerateStressSeed
+ * @run driver compiler.debug.TestGenerateStressSeed StressLCM
+ * @run driver compiler.debug.TestGenerateStressSeed StressGCM
+ * @run driver compiler.debug.TestGenerateStressSeed StressIGVN
  */
 
 public class TestGenerateStressSeed {
@@ -47,17 +49,18 @@ static void sum(int n) {
     }
 
     public static void main(String[] args) throws Exception {
-        if (args.length == 0) {
+        if (args[0].startsWith("Stress")) {
             String className = TestGenerateStressSeed.class.getName();
+            String stressOpt = args[0];
             String log = "test.log";
             String[] procArgs = {
                 "-Xcomp", "-XX:-TieredCompilation", "-XX:+UnlockDiagnosticVMOptions",
-                "-XX:CompileOnly=" + className + "::sum", "-XX:+StressIGVN",
+                "-XX:CompileOnly=" + className + "::sum", "-XX:+" + stressOpt,
                 "-XX:+LogCompilation", "-XX:LogFile=" + log, className, "10"};
             ProcessTools.createJavaProcessBuilder(procArgs).start().waitFor();
             new OutputAnalyzer(Paths.get(log))
                 .shouldContain("stress_test seed");
-        } else if (args.length > 0) {
+        } else {
             sum(Integer.parseInt(args[0]));
         }
     }

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

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2020, 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.debug;
+
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.Asserts;
+
+/*
+ * @test
+ * @bug 8253765
+ * @requires vm.debug == true & vm.compiler2.enabled
+ * @summary Tests that, when compiling with StressLCM or StressGCM, using the
+ *          same seed results in the same compilation, and using different seeds
+ *          results in different compilations (the latter does not necessarily
+ *          hold for all pairs of seeds). The output of PrintOptoStatistics is
+ *          used to compare among compilations, instead of the more intuitive
+ *          TraceOptoPipelining which prints non-deterministic memory addresses.
+ * @library /test/lib /
+ * @run driver compiler.debug.TestStressCM StressLCM
+ * @run driver compiler.debug.TestStressCM StressGCM
+ */
+
+public class TestStressCM {
+
+    static String optoStats(String stressOpt, int stressSeed) throws Exception {
+        String className = TestStressCM.class.getName();
+        String[] procArgs = {
+            "-Xcomp", "-XX:-TieredCompilation",
+            "-XX:CompileOnly=" + className + "::sum",
+            "-XX:+PrintOptoStatistics", "-XX:+" + stressOpt,
+            "-XX:StressSeed=" + stressSeed, className, "10"};
+        ProcessBuilder pb  = ProcessTools.createJavaProcessBuilder(procArgs);
+        OutputAnalyzer out = new OutputAnalyzer(pb.start());
+        return out.getStdout();
+    }
+
+    static void sum(int n) {
+        int acc = 0;
+        for (int i = 0; i < n; i++) acc += i;
+        System.out.println(acc);
+    }
+
+    public static void main(String[] args) throws Exception {
+        if (args[0].startsWith("Stress")) {
+            String stressOpt = args[0];
+            Asserts.assertEQ(optoStats(stressOpt, 10), optoStats(stressOpt, 10),
+                "got different optimization stats for the same seed");
+            Asserts.assertNE(optoStats(stressOpt, 10), optoStats(stressOpt, 20),
+                "got the same optimization stats for different seeds");
+        } else if (args.length > 0) {
+            sum(Integer.parseInt(args[0]));
+        }
+    }
+}

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

@@ -33,7 +33,8 @@
  * @requires vm.debug == true & vm.compiler2.enabled
  * @summary Tests that compilations with the same seed yield the same IGVN
  *          trace, and compilations with different seeds yield different IGVN
- *          traces.
+ *          traces (the latter does not necessarily hold for all pairs of
+ *          seeds).
  * @library /test/lib /
  * @run driver compiler.debug.TestStressIGVN
  */

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

@@ -23,6 +23,7 @@
 
 /*
  * @test
+ * @key stress randomness
  * @bug 8241900
  * @summary Loop unswitching may cause dependence on null check to be lost
  *

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

@@ -23,6 +23,7 @@
 
 /**
  * @test
+ * @key stress randomness
  * @bug 8069191
  * @summary predicate moved out of loops and CastPP removal causes dependency to be lost
  *

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

@@ -23,6 +23,7 @@
 
 /*
  * @test
+ * @key stress randomness
  * @requires vm.gc.Z
  * @bug 8237859
  * @summary A LoadP node has a wrong control input (too early) which results in an out-of-bounds read of an object array with ZGC.

test/hotspot/jtreg/compiler/membars/DekkerTest.java

@@ -23,6 +23,7 @@
 
 /**
  * @test
+ * @key stress randomness
  * @bug 8007898
  * @summary Incorrect optimization of Memory Barriers in Matcher::post_store_load_barrier().
  * @run main/othervm -Xbatch -XX:+UnlockDiagnosticVMOptions -XX:+IgnoreUnrecognizedVMOptions

test/hotspot/jtreg/gc/shenandoah/compiler/TestExpandedWBLostNullCheckDep.java

@@ -23,6 +23,7 @@
 
 /**
  * @test TestExpandedWBLostNullCheckDep
+ * @key stress randomness
  * @summary Logic that moves a null check in the expanded barrier may cause a memory access that doesn't depend on the barrier to bypass the null check
  * @requires vm.gc.Shenandoah
  * @requires vm.flavor == "server"

test/hotspot/jtreg/gc/shenandoah/compiler/TestWriteBarrierClearControl.java

@@ -23,6 +23,7 @@
 
 /**
  * @test TestWriteBarrierClearControl
+ * @key stress randomness
  * @summary Clearing control during final graph reshape causes memory barrier to loose dependency on null check
  * @requires vm.gc.Shenandoah
  * @requires vm.flavor == "server"