8323972: C2 compilation fails with assert(!x->as_Loop()->is_loop_nest_inner_loop()) failed: loop was transformed

Reviewed-by: chagedorn, epeter

Author: rwestrel

src/hotspot/share/opto/loopnode.cpp

@@ -940,12 +940,20 @@ bool PhaseIdealLoop::create_loop_nest(IdealLoopTree* loop, Node_List &old_new) {
   // inner_iters_max may not fit in a signed integer (iterating from
   // Long.MIN_VALUE to Long.MAX_VALUE for instance). Use an unsigned
   // min.
-  Node* inner_iters_actual = MaxNode::unsigned_min(inner_iters_max, inner_iters_limit, TypeInteger::make(0, iters_limit, Type::WidenMin, bt), _igvn);
+  const TypeInteger* inner_iters_actual_range = TypeInteger::make(0, iters_limit, Type::WidenMin, bt);
+  Node* inner_iters_actual = MaxNode::unsigned_min(inner_iters_max, inner_iters_limit, inner_iters_actual_range, _igvn);
 
   Node* inner_iters_actual_int;
   if (bt == T_LONG) {
     inner_iters_actual_int = new ConvL2INode(inner_iters_actual);
     _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
+    // When the inner loop is transformed to a counted loop, a loop limit check is not expected to be needed because
+    // the loop limit is less or equal to max_jint - stride - 1 (if stride is positive but a similar argument exists for
+    // a negative stride). We add a CastII here to guarantee that, when the counted loop is created in a subsequent loop
+    // opts pass, an accurate range of values for the limits is found.
+    const TypeInt* inner_iters_actual_int_range = TypeInt::make(0, iters_limit, Type::WidenMin);
+    inner_iters_actual_int = new CastIINode(outer_head, inner_iters_actual_int, inner_iters_actual_int_range, ConstraintCastNode::UnconditionalDependency);
+    _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
   } else {
     inner_iters_actual_int = inner_iters_actual;
   }

test/hotspot/jtreg/compiler/longcountedloops/TestInaccurateInnerLoopLimit.java

@@ -0,0 +1,42 @@
+/*
+ * 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 8323972
+ * @summary C2 compilation fails with assert(!x->as_Loop()->is_loop_nest_inner_loop()) failed: loop was transformed
+ *
+ * @run main/othervm -Xcomp -XX:CompileCommand=compileonly,TestInaccurateInnerLoopLimit::test* -XX:-TieredCompilation TestInaccurateInnerLoopLimit
+ *
+ */
+
+public class TestInaccurateInnerLoopLimit {
+
+    public static void main(String args[]) {
+        test();
+    }
+
+    public static void test() {
+        for (long i = 9223372034707292164L; i > 9223372034707292158L; i += -2L) { }
+    }
+}