1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
|
/*
* Copyright (C) 2024 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.lang.reflect.Field;
import sun.misc.Unsafe;
public class Main {
private static Unsafe getUnsafe() throws NoSuchFieldException, IllegalAccessException {
Class<?> unsafeClass = Unsafe.class;
Field f = unsafeClass.getDeclaredField("theUnsafe");
f.setAccessible(true);
return (Unsafe) f.get(null);
}
private static Unsafe unsafe;
static void assertEquals(int expected, int actual) {
if (expected != actual) {
throw new Error("Expected " + expected + ", got " + actual);
}
}
public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
unsafe = getUnsafe();
testPutZero();
testPutFixedOffset();
assertEquals(0, testGet());
assertEquals(42, testGetFar());
testGetAndPutAbsoluteAddress();
}
/// CHECK-START-ARM64: void Main.testPutZero() disassembly (after)
/// CHECK: str wzr, [x{{[0-9]+}}, #12]
private static void testPutZero() {
int[] object = new int[42];
unsafe.putInt(object, unsafe.arrayBaseOffset(int[].class), 0);
}
/// CHECK-START-ARM64: void Main.testPutFixedOffset() disassembly (after)
/// CHECK: stur w{{[0-9]+}}, [x{{[0-9]+}}, #38]
private static void testPutFixedOffset() {
int[] object = new int[42];
unsafe.putInt(object, 38, 12);
}
/// CHECK-START-ARM64: int Main.testGet() disassembly (after)
/// CHECK: ldur w{{[0-9]+}}, [x{{[0-9]+}}, #38]
private static int testGet() {
int[] object = new int[42];
return unsafe.getInt(object, 38);
}
private static int testGetFar() {
int offset = 32 * 1024;
int arraySize = offset / 4;
int[] object = new int[arraySize];
unsafe.putInt(object, offset, 42);
return unsafe.getInt(object, offset);
}
/// CHECK-START: int Main.testArrayBaseOffsetObject() instruction_simplifier (after)
/// CHECK: IntConstant 12
private static int testArrayBaseOffsetObject() {
return unsafe.arrayBaseOffset(Object[].class);
}
/// CHECK-START: int Main.testArrayBaseOffsetInt() instruction_simplifier (after)
/// CHECK: IntConstant 12
private static int testArrayBaseOffsetInt() {
return unsafe.arrayBaseOffset(int[].class);
}
/// CHECK-START: int Main.testArrayBaseOffsetDouble() instruction_simplifier (after)
/// CHECK: IntConstant 16
private static int testArrayBaseOffsetDouble() {
return unsafe.arrayBaseOffset(double[].class);
}
private static void testGetAndPutAbsoluteAddress() {
long address = 0;
try {
address = unsafe.allocateMemory(4);
$noinline$unsafePutAbsoluteInt(address, 0xDEADBEEF);
assertEquals(0xDEADBEEF, $noinline$unsafeGetAbsoluteInt(address));
} finally {
if (address != 0) {
unsafe.freeMemory(address);
}
}
}
/// CHECK-START: void Main.$noinline$unsafePutAbsoluteInt(long, int) builder (after)
/// CHECK: InvokeVirtual intrinsic:UnsafePutAbsolute
private static void $noinline$unsafePutAbsoluteInt(long address, int value) {
unsafe.putInt(address, value);
}
/// CHECK-START: int Main.$noinline$unsafeGetAbsoluteInt(long) builder (after)
/// CHECK: InvokeVirtual intrinsic:UnsafeGetAbsolute
private static int $noinline$unsafeGetAbsoluteInt(long address) {
return unsafe.getInt(address);
}
}
|