在IL中看起来像什么？ [英] What does an if look like in IL?

问题描述

if 语句在编译成IL时是什么样的？

What does an if statement look like when it's compiled into IL?

这是一个非常简单的构造C＃。 sombody能给我一个更抽象的定义吗？

It's a very simple construct in C#. Can sombody give me a more abstract definition of what it really is?

推荐答案

这里有一些如果语句以及它们如何转换为IL：

Here are a few if statements and how they translate to IL:

ldc.i4.s 0x2f                      var i = 47;
stloc.0 

ldloc.0                            if (i == 47)
ldc.i4.s 0x2f
bne.un.s L_0012

ldstr "forty-seven!"                   Console.WriteLine("forty-seven!");
call Console::WriteLine

L_0012:
ldloc.0                            if (i > 0)
ldc.i4.0 
ble.s L_0020

ldstr "greater than zero!"             Console.WriteLine("greater than zero!");
call Console::WriteLine

L_0020:
ldloc.0                            bool b = (i != 0);
ldc.i4.0 
ceq 
ldc.i4.0 
ceq 
stloc.1 

ldloc.1                            if (b)
brfalse.s L_0035

ldstr "boolean true!"                  Console.WriteLine("boolean true!");
call Console::WriteLine

L_0035:
ret

有一点需要注意：IL指令总是相反。 如果（i> 0）转换为有效意味着如果 i< = 0 ，则跳过的主体，如果阻止。

One thing to note here: The IL instructions are always the "opposite". if (i > 0) translates to something that effectively means "if i <= 0, then jump over the body of the if block".

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