1 /* 2 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 /* 25 * @test TestMembarDependencies 26 * @bug 8172850 27 * @summary Tests correct scheduling of memory loads around MembarVolatile emitted by GC barriers. 28 * @library /testlibrary 29 * @run driver compiler.membars.TestMembarDependencies 30 */ 31 32 package compiler.membars; 33 34 import com.oracle.java.testlibrary.*; 35 36 public class TestMembarDependencies { 37 private static TestMembarDependencies f1; 38 private static TestMembarDependencies f2; 39 main(String args[])40 public static void main(String args[]) throws Throwable { 41 if (args.length == 0) { 42 // For debugging, add "-XX:+TraceOptoPipelining" 43 OutputAnalyzer oa = ProcessTools.executeTestJvm("-XX:+IgnoreUnrecognizedVMOptions", 44 "-XX:-TieredCompilation", "-XX:-BackgroundCompilation", "-XX:+PrintOpto", 45 "-XX:CompileCommand=compileonly,compiler.membars.TestMembarDependencies::test*", 46 "-XX:CompileCommand=dontinline,compiler.membars.TestMembarDependencies::test_m1", 47 TestMembarDependencies.class.getName(), "run"); 48 // C2 should not crash or bail out from compilation 49 oa.shouldHaveExitValue(0); 50 oa.shouldNotMatch("Bailout: Recompile without subsuming loads"); 51 System.out.println(oa.getOutput()); 52 } else { 53 f2 = new TestMembarDependencies(); 54 // Trigger compilation of test1 and test2 55 for (int i = 0; i < 10_000; ++i) { 56 f2.test1(f2); 57 f2.test2(f2); 58 } 59 } 60 } 61 test_m1()62 public void test_m1() { } test_m2()63 public void test_m2() { } 64 test1(TestMembarDependencies obj)65 public void test1(TestMembarDependencies obj) { 66 // Try/catch/finally is used to create a CFG block without a test + jmpCon 67 // allowing GCM to schedule the testN_mem_reg0 instruction into that block. 68 try { 69 // Method call defines memory state that is then 70 // used by subsequent instructions/blocks (see below). 71 test_m1(); 72 } catch (Exception e) { 73 74 } finally { 75 // Oop write to field emits a GC post-barrier with a MembarVolatile 76 // which has a wide memory effect (kills all memory). This creates an 77 // anti-dependency on all surrounding memory loads. 78 f1 = obj; 79 } 80 // The empty method m2 is inlined but the null check of f2 remains. It is encoded 81 // as CmpN(LoadN(MEM), NULL) where MEM is the memory after the call to test_m1(). 82 // This is matched to testN_mem_reg0 on x86 which is scheduled before the barrier 83 // in the try/catch block due to the anti-dependency on the MembarVolatile. 84 // C2 crashes in the register allocator when trying to spill the flag register 85 // to keep the result of the testN instruction live from the try/catch block 86 // until it is here. 87 f2.test_m2(); 88 } 89 test2(TestMembarDependencies obj)90 public void test2(TestMembarDependencies obj) { 91 // Same as test1 but without try/catch/finally. 92 // This causes C2 to bail out in block local scheduling because testN_mem_reg0 is 93 // scheduled into a block that already contains another test + jmpCon instruction. 94 test_m1(); 95 f1 = obj; 96 f2.test_m2(); 97 } 98 } 99