8247307: C2: Loop array fill stub routines are not called

Ignore safepoint polling use of CountedLoopNode when matching loop array fill pattern.

Reviewed-by: kvn, thartmann

src/hotspot/cpu/x86/vm_version_x86.cpp

@@ -1507,6 +1507,12 @@ void VM_Version::get_processor_features() {
     // Modern processors allow misaligned memory operations for vectors.
     AlignVector = !UseUnalignedLoadStores;
   }
+  if (FLAG_IS_DEFAULT(OptimizeFill)) {
+    // 8247307: On x86, the auto-vectorized loop array fill code shows
+    // better performance than the array fill stubs. We should reenable
+    // this after the x86 stubs get improved.
+    OptimizeFill = false;
+  }
 #endif // COMPILER2
 
   if (FLAG_IS_DEFAULT(AllocatePrefetchInstr)) {

src/hotspot/share/opto/loopTransform.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2020, 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
@@ -3642,10 +3642,21 @@ bool PhaseIdealLoop::match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& st
     for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
       Node* use = iter.get();
       if (!lpt->_body.contains(use)) {
-        msg = "node is used outside loop";
-        // lpt->_body.dump();
-        msg_node = n;
-        break;
+        if (n->is_CountedLoop() && n->as_CountedLoop()->is_strip_mined()) {
+          // In strip-mined counted loops, the CountedLoopNode may be
+          // used by the address polling node of the outer safepoint.
+          // Skip this use because it's safe.
+#ifdef ASSERT
+          Node* sfpt = n->as_CountedLoop()->outer_safepoint();
+          Node* polladr = sfpt->in(TypeFunc::Parms+0);
+          assert(use == polladr, "the use should be a safepoint polling");
+#endif
+          continue;
+        } else {
+          msg = "node is used outside loop";
+          msg_node = n;
+          break;
+        }
       }
     }
   }

test/micro/org/openjdk/bench/vm/compiler/ArrayFill.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, Arm Limited. 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 org.openjdk.bench.vm.compiler;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+
+import java.util.concurrent.TimeUnit;
+import java.util.Arrays;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+public class ArrayFill {
+    @Param("65536") private int size;
+
+    private byte[] ba;
+    private short[] sa;
+    private int[] ia;
+
+    @Setup
+    public void setup() {
+        ba = new byte[size];
+        sa = new short[size];
+        ia = new int[size];
+    }
+
+    @Benchmark
+    public void fillByteArray() {
+        for (int i = 0; i < size; i++) {
+            ba[i] = (byte) 123;
+        }
+    }
+
+    @Benchmark
+    public void fillShortArray() {
+        for (int i = 0; i < size; i++) {
+            sa[i] = (short) 12345;
+        }
+    }
+
+    @Benchmark
+    public void fillIntArray() {
+        for (int i = 0; i < size; i++) {
+            ia[i] = 1234567890;
+        }
+    }
+
+    @Benchmark
+    public void zeroByteArray() {
+        for (int i = 0; i < size; i++) {
+            ba[i] = 0;
+        }
+    }
+
+    @Benchmark
+    public void zeroShortArray() {
+        for (int i = 0; i < size; i++) {
+            sa[i] = 0;
+        }
+    }
+
+    @Benchmark
+    public void zeroIntArray() {
+        for (int i = 0; i < size; i++) {
+            ia[i] = 0;
+        }
+    }
+}
+