PC 寄存器介绍
PC 寄存器的作用
PC寄存器用来存储指向下一条指令的地址,也即将要执行的指令代码。由执行引擎将指令解释为机器码交由cpu进行处理
public class PCRegisterTest {
public static void main(String[] args) {
int i = 10;
int j = 20;
int k = i + j;
String s = "abc";
System.out.println(i);
System.out.println(k);
}
}
12345678910111213
Constant pool:
#1 = Methodref #6.#26 // java/lang/Object."<init>":()V
#2 = String #27 // abc
#3 = Fieldref #28.#29 // java/lang/System.out:Ljava/io/PrintStream;
#4 = Methodref #30.#31 // java/io/PrintStream.println:(I)V
#5 = Class #32 // com/atguigu/java/PCRegisterTest
#6 = Class #33 // java/lang/Object
#7 = Utf8 <init>
#8 = Utf8 ()V
#9 = Utf8 Code
#10 = Utf8 LineNumberTable
#11 = Utf8 LocalVariableTable
#12 = Utf8 this
#13 = Utf8 Lcom/atguigu/java/PCRegisterTest;
#14 = Utf8 main
#15 = Utf8 ([Ljava/lang/String;)V
#16 = Utf8 args
#17 = Utf8 [Ljava/lang/String;
#18 = Utf8 i
#19 = Utf8 I
#20 = Utf8 j
#21 = Utf8 k
#22 = Utf8 s
#23 = Utf8 Ljava/lang/String;
#24 = Utf8 SourceFile
#25 = Utf8 PCRegisterTest.java
#26 = NameAndType #7:#8 // "<init>":()V
#27 = Utf8 abc
#28 = Class #34 // java/lang/System
#29 = NameAndType #35:#36 // out:Ljava/io/PrintStream;
#30 = Class #37 // java/io/PrintStream
#31 = NameAndType #38:#39 // println:(I)V
#32 = Utf8 com/atguigu/java/PCRegisterTest
#33 = Utf8 java/lang/Object
#34 = Utf8 java/lang/System
#35 = Utf8 out
#36 = Utf8 Ljava/io/PrintStream;
#37 = Utf8 java/io/PrintStream
#38 = Utf8 println
#39 = Utf8 (I)V
{
public com.atguigu.java.PCRegisterTest();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 7: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this Lcom/atguigu/java/PCRegisterTest;
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=5, args_size=1
0: bipush 10
2: istore_1
3: bipush 20
5: istore_2
6: iload_1
7: iload_2
8: iadd
9: istore_3
10: ldc #2 // String abc
12: astore 4
14: getstatic #3 // Field java/lang/System.out:Ljava/io/PrintStream;
17: iload_1
18: invokevirtual #4 // Method java/io/PrintStream.println:(I)V
21: getstatic #3 // Field java/lang/System.out:Ljava/io/PrintStream;
24: iload_3
25: invokevirtual #4 // Method java/io/PrintStream.println:(I)V
28: return
LineNumberTable:
line 10: 0
line 11: 3
line 12: 6
line 14: 10
line 15: 14
line 16: 21
line 18: 28
LocalVariableTable:
Start Length Slot Name Signature
0 29 0 args [Ljava/lang/String;
3 26 1 i I
6 23 2 j I
10 19 3 k I
14 15 4 s Ljava/lang/String;
使用PC寄存器存储字节码指令地址有什么用呢? 或者问 为什么使用 PC 寄存器来记录当前线程的执行地址呢?
PC寄存器为什么被设定为私有的?