8353341: C2: removal of a Mod[DF]Node crashes when the node is already dead

Reviewed-by: thartmann, chagedorn

Author: marc-chevalier

src/hotspot/share/opto/divnode.cpp

@@ -1518,7 +1518,8 @@ Node* ModFNode::Ideal(PhaseGVN* phase, bool can_reshape) {
   PhaseIterGVN* igvn = phase->is_IterGVN();
 
   bool result_is_unused = proj_out_or_null(TypeFunc::Parms) == nullptr;
-  if (result_is_unused) {
+  bool not_dead = proj_out_or_null(TypeFunc::Control) != nullptr;
+  if (result_is_unused && not_dead) {
     return replace_with_con(igvn, TypeF::make(0.));
   }
 
@@ -1569,7 +1570,8 @@ Node* ModDNode::Ideal(PhaseGVN* phase, bool can_reshape) {
   PhaseIterGVN* igvn = phase->is_IterGVN();
 
   bool result_is_unused = proj_out_or_null(TypeFunc::Parms) == nullptr;
-  if (result_is_unused) {
+  bool not_dead = proj_out_or_null(TypeFunc::Control) != nullptr;
+  if (result_is_unused && not_dead) {
     return replace_with_con(igvn, TypeD::make(0.));
   }
 

test/hotspot/jtreg/compiler/c2/irTests/FPModWithoutControlProj.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2025, 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.c2.irTests;
+
+import compiler.lib.ir_framework.*;
+
+/*
+ * @test
+ * @bug 8353341
+ * @summary Test that Ideal transformations of Mod[DF]Node are not crashing
+ *          when control proj is absent, and the node is still removed.
+ * @library /test/lib /
+ * @run driver compiler.c2.irTests.FPModWithoutControlProj
+ */
+public class FPModWithoutControlProj {
+    static int y;
+    static public boolean flag;
+    static int iArr[];
+
+    public static void main(String[] args) {
+        TestFramework.runWithFlags("-XX:+StressIGVN");
+    }
+
+    @Run(test = {"testD", "testF"})
+    public void runMethod() {
+        testD();
+        testF();
+    }
+
+    @Test
+    @IR(failOn = {IRNode.MOD_D, IRNode.MOD_F})
+    public void testD() {
+        int x = 243;
+        double f1 = 119.303D, f2 = 2.637D;
+
+        for (int i11 = 0; i11 < 100; i11++) {
+            if (flag) {
+            } else if (flag) {
+                do {
+                    for (f2 = 3; ; f2--) {
+                        if (f2 % 3 == 1) {
+                            x -= y;
+                        }
+                        iArr[1] += 5;
+                    }
+                } while (f1 < 234);
+            }
+        }
+    }
+
+    @Test
+    @IR(failOn = {IRNode.MOD_D, IRNode.MOD_F})
+    public void testF() {
+        int x = 243;
+        float f1 = 119.303F, f2 = 2.637F;
+
+        for (int i11 = 0; i11 < 100; i11++) {
+            if (flag) {
+            } else if (flag) {
+                do {
+                    for (f2 = 3; ; f2--) {
+                        if (f2 % 3 == 1) {
+                            x -= y;
+                        }
+                        iArr[1] += 5;
+                    }
+                } while (f1 < 234);
+            }
+        }
+    }
+}