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]));
         }
     }