8323101: C2: assert(n->in(0) == nullptr) failed: divisions with zero …

…check should already have bailed out earlier in split-if

Reviewed-by: kvn, thartmann

src/hotspot/share/opto/loopopts.cpp

@@ -287,7 +287,11 @@ bool PhaseIdealLoop::cannot_split_division(const Node* n, const Node* region) co
       return false;
   }
 
-  assert(n->in(0) == nullptr, "divisions with zero check should already have bailed out earlier in split-if");
+  if (n->in(0) != nullptr) {
+    // Cannot split through phi if Div or Mod node has a control dependency to a zero check.
+    return true;
+  }
+
   Node* divisor = n->in(2);
   return is_divisor_counted_loop_phi(divisor, region) &&
          loop_phi_backedge_type_contains_zero(divisor, zero);

test/hotspot/jtreg/compiler/splitif/TestSplitDivThroughPhiWithControl.java

@@ -0,0 +1,210 @@
+/*
+ * Copyright (c) 2024, 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.
+ */
+
+/*
+ * @test id=normal
+ * @bug 8323101
+ * @summary Test split_thru_phi with pinned divisions/modulo that have phi as inputs.
+ * @run main/othervm -Xbatch
+ *                   -XX:CompileCommand=compileonly,compiler.splitif.TestSplitDivThroughPhiWithControl::*
+ *                   compiler.splitif.TestSplitDivThroughPhiWithControl
+ */
+
+/*
+ * @test id=fuzzer
+ * @bug 8323101
+ * @summary Test split_thru_phi with pinned divisions/modulo that have phi as inputs.
+ * @run main/othervm -Xbatch -XX:PerMethodTrapLimit=0
+ *                   -XX:CompileCommand=compileonly,compiler.splitif.TestSplitDivThroughPhiWithControl::*
+ *                   compiler.splitif.TestSplitDivThroughPhiWithControl
+ */
+
+package compiler.splitif;
+
+public class TestSplitDivThroughPhiWithControl {
+    static int divisorInt = 34;
+    static int iFld;
+    static int x;
+    static int y;
+    static long divisorLong = 34L;
+    static long lFld;
+    static long lFld2;
+    static long lFld3;
+    static boolean flag;
+
+    static int[] iArr = new int[400];
+
+    public static void main(String[] strArr) {
+        iArr[0] = 52329;
+        for (int i = 0; i < 10000; i++) {
+            flag = i % 3 == 0;                 // Avoid unstable if trap
+            divisorInt = i % 2 == 0 ? 0 : 23;  // Avoid div by zero trap
+            divisorLong = divisorInt;          // Avoid div by zero trap
+            try {
+                testIntDiv();
+            } catch (ArithmeticException e) {
+                // Expected.
+            }
+
+            try {
+                testIntMod();
+            } catch (ArithmeticException e) {
+                // Expected.
+            }
+
+            try {
+                testLongDiv(); // Currently does not trigger due to JDK-8323652
+            } catch (ArithmeticException e) {
+                // Expected.
+            }
+
+            try {
+                testLongMod(); // Currently does not trigger due to JDK-8323652
+            } catch (ArithmeticException e) {
+                // Expected.
+            }
+
+            testFuzzer();
+        }
+    }
+
+    static void testIntDiv() {
+        int a;
+
+        for (int j = 0; j < 100; j++) {
+            y += 5;
+            int sub = j - 3; // AddI
+            int div = (sub / divisorInt); // DivI with AddI input
+
+            if (flag) {
+                a = y;
+            } else {
+                a = 2;
+            }
+            // Region
+
+            // Use StoreI with AddI input. Store needs to be split through Region in Split-If which is done together
+            // with AddI.
+            iFld = sub;
+
+            if (a < 3) { // If that's split in Split-If
+                // Use of DivI -> after Split-If, DivI gets a Phi input that merges the split AddI nodes.
+                // -> triggers assert that we should not find pinned div nodes in cannot_split_division().
+                x = div;
+            }
+        }
+    }
+
+    // Same as testIntDiv() but with ModI
+    static void testIntMod() {
+        int a;
+
+        for (int j = 0; j < 100; j++) {
+            y += 5;
+            int sub = j - 3;
+            int mod = (sub % divisorInt);
+
+            if (flag) {
+                a = y;
+            } else {
+                a = 2;
+            }
+
+            iFld = sub;
+
+            if (a < 3) {
+                x = mod; // Only StoreI visited first but not mod since it's an input
+            }
+        }
+    }
+
+    // Same as testIntDiv() but with DivL
+    static void testLongDiv() {
+        long a;
+
+        for (int j = 0; j < 100; j++) {
+            y += 5;
+            long sub = j - 3;
+            long div = (sub / divisorLong);
+
+            if (flag) {
+                a = lFld2;
+            } else {
+                a = 2;
+            }
+
+            lFld = sub;
+
+            if (a < 3) {
+                lFld3 = div;
+            }
+        }
+    }
+
+
+    // Same as testIntDiv() but with ModL
+    static void testLongMod() {
+        long a;
+
+        for (long j = 0; j < 100; j++) {
+            lFld2 += 5;
+            long sub = j - 3;
+            long mod = (sub % divisorLong);
+
+            if (flag) {
+                a = lFld2;
+            } else {
+                a = 2;
+            }
+
+            lFld = sub;
+
+            if (a < 3) {
+                lFld3 = mod; // Only StoreI visited first but not mod since it's an input
+            }
+        }
+    }
+
+    // Original fuzzer crash
+    static void testFuzzer() {
+        int i19, i21 = 4928, i23 = 14;
+        for (int i = 5; i < 100; i++) {
+            i19 = i23;
+            int j = 1;
+            while (true) {
+                try {
+                    i21 = (iArr[0] / 34);
+                    i23 = (j % i21);
+                } catch (ArithmeticException a_e) {
+                }
+                iArr = iArr;
+                iFld = i21;
+                iArr[1] += 5;
+                if (j == 1000) {
+                    break;
+                }
+                j++;
+            }
+        }
+    }
+}