为什么 C# 编译器在 IL 中发出额外的操作码？

发布于 2024-12-08 14:06:54 字数 989 浏览 1 评论 0原文

如果我有一个方法 Multiply 定义为：

public static class Experiment
{
    public static int Multiply(int a, int b)
    {
        return a * b;
    }
}

那么为什么编译器会发出这个 IL：

.method public hidebysig static int32 Multiply(int32 a, int32 b) cil managed
{
    .maxstack 2              //why is it not 16?
    .locals init (
        [0] int32 CS$1$0000) //what is this?
    L_0000: nop              //why this?
    L_0001: ldarg.0 
    L_0002: ldarg.1 
    L_0003: mul 
    L_0004: stloc.0          //why this?
    L_0005: br.s L_0007      //why this?
    L_0007: ldloc.0          //why this?
    L_0008: ret 
}

如您所见，它还包含一些对我来说没有意义的附加操作码，而事实上我期望下面的 IL:

.method public hidebysig static int32 MyMethod(int32 a, int32 b) cil managed
{
    .maxstack 16
    L_0000: ldarg.0 
    L_0001: ldarg.1 
    L_0002: mul 
    L_0003: ret 
}

做同样的事情。

所以问题是，为什么编译器会在 IL 中发出额外的操作码？

我正在使用调试模式。

原文

If I've a method Multiply defined as:

public static class Experiment
{
    public static int Multiply(int a, int b)
    {
        return a * b;
    }
}

Then why does the compiler emit this IL:

.method public hidebysig static int32 Multiply(int32 a, int32 b) cil managed
{
    .maxstack 2              //why is it not 16?
    .locals init (
        [0] int32 CS$1$0000) //what is this?
    L_0000: nop              //why this?
    L_0001: ldarg.0 
    L_0002: ldarg.1 
    L_0003: mul 
    L_0004: stloc.0          //why this?
    L_0005: br.s L_0007      //why this?
    L_0007: ldloc.0          //why this?
    L_0008: ret 
}

As you can see, it also contains some additional OpCodes which don't make sense to me, when in fact I expect the following IL:

.method public hidebysig static int32 MyMethod(int32 a, int32 b) cil managed
{
    .maxstack 16
    L_0000: ldarg.0 
    L_0001: ldarg.1 
    L_0002: mul 
    L_0003: ret 
}

which does the very same thing.

So the question is, why does the compiler emit additional OpCodes in IL?

I'm using Debug mode.

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