8331717: C2: Crash with SIGFPE Because Loop Predication Wrongly Hoists Division Requiring Zero Check

Reviewed-by: chagedorn, qamai, kvn

Author: Theo Weidmann

src/hotspot/share/opto/loopPredicate.cpp

@@ -469,7 +469,7 @@ class Invariance : public StackObj {
           // loop, it was marked invariant but n is only invariant if
           // it depends only on that test. Otherwise, unless that test
           // is out of the loop, it's not invariant.
-          if (n->is_CFG() || n->depends_only_on_test() || n->in(0) == nullptr || !_phase->is_member(_lpt, n->in(0))) {
+          if (n->is_CFG() || (n->depends_only_on_test() && _phase->igvn().no_dependent_zero_check(n)) || n->in(0) == nullptr || !_phase->is_member(_lpt, n->in(0))) {
             _invariant.set(n->_idx); // I am a invariant too
           }
         }

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

@@ -0,0 +1,89 @@
+/*
+ * 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
+ * @bug 8331717
+ * @summary C2: Crash with SIGFPE
+ *
+ * @run main/othervm -XX:CompileCommand=compileonly,*TestLoopPredicationDivZeroCheck*::* -XX:-TieredCompilation -Xbatch TestLoopPredicationDivZeroCheck
+ */
+
+public class TestLoopPredicationDivZeroCheck {
+    static int iArr[] = new int[100];
+    static volatile long lFld;
+    static int iFld;
+
+    public static void main(String[] strArr) {
+        for (int i = 0; i < 10000; i++) {
+            test();
+        }
+        for (int i = 0; i < 10000; i++) {
+            test2();
+        }
+    }
+
+    /*
+     * The division 2 / i4 requires a non-zero check. As the result is an array access, it will be the input to a range
+     * check. Loop predication will try to move the range check and the division to right before the loop as the division
+     * appears to be invariant (i4 is always 0). However, the division is not truly invariant as it requires the zero
+     * check for i4 that can throw an exception. The bug fixed in 8331717 caused the division to still be moved before the
+     * for loop with the range check.
+     */
+    static void test() {
+        int i1 = 0;
+
+        for (int i4 : iArr) {
+            i4 = i1;
+            try {
+                iArr[0] = 1 / i4;
+                i4 = iArr[2 / i4];
+           } catch (ArithmeticException a_e) {
+           }
+       }
+    }
+
+    /*
+     * Loop predication will try to move 3 / y (input to the range check for bArr[x / 30]) before its containing for loop
+     * but it may not as y must be zero-checked. The same problem as above occurred before the fix in 8331717.
+     */
+    static void test2() {
+        int x = 0;
+        int y = iFld;
+        long lArr[] = new long[400];
+        boolean bArr[] = new boolean[400];
+        for (int i = 0; i < 10000; i++) {
+            for (int j = 1; j < 13; j++) {
+                for (int k = 1; k < 2; k++) {
+                    lFld = 0;
+                    lArr[1] = 7;
+                    try {
+                        x = 3 / y;
+                    } catch (ArithmeticException a_e) {
+                    }
+                    bArr[x / 30] = true;
+                }
+            }
+        }
+    }
+}