我正在检查kotlinc
个捕获lambda的字节码。并试图了解生成的字节码具有nop
指令的原因。
kotlinc -jvm-target 1.6 .
private inline fun lambdaCapturing(f: () -> Int): Int = f()
fun main(args: Array<String>) {
lambdaCapturing { 42 }
}
结果我得到
public final class x.y.z.LambdaCaptKt {
private static final int lambdaCapturing(kotlin.jvm.functions.Function0<java.lang.Integer>);
Code:
0: ldc #8 // int 0
2: istore_1
3: aload_0
4: invokeinterface #14,1 // InterfaceMethod kotlin/jvm/functions/Function0.invoke:()Ljava/lang/Object;
9: checkcast #16 // class java/lang/Number
12: invokevirtual #20 // Method java/lang/Number.intvalue:()I
15: ireturn
public static final void main(java.lang.String[]);
Code:
0: aload_0
1: ldc #29 // String args
3: invokestatic #35 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsnotNull:(Ljava/lang/Object;Ljava/lang/String;)V
6: iconst_0
7: istore_1
8: iconst_0
9: istore_2
10: nop
11: nop
12: nop
13: return
}
在主要功能中带有多条nop
指令。
如果我将使用-Xno-optimize
编译相同的代码段,则main
函数将类似于
public static final void main(java.lang.String[]);
Code:
0: aload_0
1: ldc #29 // String args
3: invokestatic #35 // Method kotlin/jvm/internal/Intrinsics.checkParameterIsnotNull:(Ljava/lang/Object;Ljava/lang/String;)V
6: nop
7: iconst_0
8: istore_1
9: nop
10: iconst_0
11: istore_2
12: bipush 10
14: nop
15: goto 18
18: invokestatic #41 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
21: checkcast #16 // class java/lang/Number
24: invokevirtual #20 // Method java/lang/Number.intvalue:()I
27: nop
28: goto 31
31: pop
32: return
也有nop
个。
- 在未经优化的代码中包含
nop
的原因是什么? (调试信息/...) - 是否有理由在优化的代码中包含
nop
?