[GR-54967] Avoid zero modulus when calling BigInteger.modPow.

PullRequest: graal/18225

Author: mur47x111

compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/GraalCompilerTest.java

@@ -1773,28 +1773,28 @@ protected CanonicalizerPhase createCanonicalizerPhase() {
     public static final String SEED_PROPERTY_NAME = "test.graal.random.seed";
 
     /**
-     * Globally shared, lazily initialized random generator.
+     * Globally shared, lazily initialized random seed.
      */
-    private static volatile Random randomGenerator;
+    private static volatile Long randomSeed;
 
     /**
-     * Returns a global {@link java.util.Random} generator. The generator is seeded with the value
-     * specified by {@link #SEED_PROPERTY_NAME} if it exists.
+     * Returns a {@link java.util.Random} generator with a global seed specified by
+     * {@link #SEED_PROPERTY_NAME} if it exists.
      *
      * The used seed printed to stdout for reproducing test failures.
      */
     public static Random getRandomInstance() {
-        if (randomGenerator == null) {
+        if (randomSeed == null) {
             synchronized (GraalCompilerTest.class) {
-                if (randomGenerator == null) {
+                if (randomSeed == null) {
                     var seedLong = Long.getLong(SEED_PROPERTY_NAME);
                     var seed = seedLong != null ? seedLong : new Random().nextLong();
                     System.out.printf("Random generator seed: %d%n", seed);
                     System.out.printf("To re-run test with same seed, set \"-D%s=%d\" on command line.%n", SEED_PROPERTY_NAME, seed);
-                    randomGenerator = new Random(seed);
+                    randomSeed = seed;
                 }
             }
         }
-        return randomGenerator;
+        return new Random(randomSeed);
     }
 }

compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/BigIntegerIntrinsicsTest.java

@@ -121,7 +121,9 @@ public void testSquareToLen() {
             BigInteger big2 = randomBig(i);
 
             // squareToLen is exercised via the call path modPow -> oddModPow -> montgomerySquare
-            expectedResults.put(Pair.create(big1, big2), big1.modPow(bigTwo, big2));
+            if (big2.signum() > 0) {
+                expectedResults.put(Pair.create(big1, big2), big1.modPow(bigTwo, big2));
+            }
         }
 
         InstalledCode intrinsic = getCode(getResolvedJavaMethod(BigInteger.class, "squareToLen"), null, true, true, GraalCompilerTest.getInitialOptions());
@@ -151,19 +153,21 @@ public void testMontgomery() throws ClassNotFoundException {
             BigInteger big1 = randomBig(i);
             BigInteger big2 = randomBig(i);
 
-            // Invoke BigInteger BigInteger.modPow(BigExp, BigInteger)
-            BigInteger res1 = (BigInteger) tin.invokeJava(big1, bigTwo, big2);
+            if (big2.signum() > 0) {
+                // Invoke BigInteger BigInteger.modPow(BigExp, BigInteger)
+                BigInteger res1 = (BigInteger) tin.invokeJava(big1, bigTwo, big2);
 
-            // Invoke BigInteger testMontgomeryAux(BigInteger, BigExp, BigInteger)
-            BigInteger res2 = (BigInteger) tin.invokeTest(big1, bigTwo, big2);
+                // Invoke BigInteger testMontgomeryAux(BigInteger, BigExp, BigInteger)
+                BigInteger res2 = (BigInteger) tin.invokeTest(big1, bigTwo, big2);
 
-            assertDeepEquals(res1, res2);
+                assertDeepEquals(res1, res2);
 
-            // Invoke BigInteger testMontgomeryAux(BigInteger, BigExp, BigInteger)
-            // through code handle.
-            BigInteger res3 = (BigInteger) tin.invokeCode(big1, bigTwo, big2);
+                // Invoke BigInteger testMontgomeryAux(BigInteger, BigExp, BigInteger)
+                // through code handle.
+                BigInteger res3 = (BigInteger) tin.invokeCode(big1, bigTwo, big2);
 
-            assertDeepEquals(res1, res3);
+                assertDeepEquals(res1, res3);
+            }
         }
     }