编译器会针对布尔赋值进行优化吗？

Question

这就是我想要做的:

if(ABoolean || (BBoolean && CBoolean))
{
    SomeButton.Enabled = true;
    AnotherButton.Enabled = true;
}
else 
{
    SomeButton.Enabled = false;
    AnotherButton.Enabled = false;
}

我可以将其切换为:

SomeButton.Enabled = (ABoolean || (BBoolean && CBoolean));
AnotherButton.Enabled = (ABoolean || (BBoolean && CBoolean));

更简洁的代码.我的问题是,编译器是否优化了赋值,以便它将看到布尔表达式相同并为第二个按钮分配其值,或者它将每次计算值.

注意:我知道这是一个简单的例子,加速/减速将是微不足道的,无法实现,但它将有助于我更好地理解编译器优化.

编辑:这就是我认为可能优化第二个选项的原因:

class Program
{
    static bool ABoolean = true, BBoolean = true, CBoolean = false;
    static bool AEnable, BEnable;


    static void Main(string[] args)
    {
        Stopwatch sw = new Stopwatch();
        sw.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            Operation1();
        }
        sw.Stop();
        Console.WriteLine(sw.ElapsedMilliseconds);

        Stopwatch sw1 = new Stopwatch();
        sw1.Start();
        for (int i = 0; i < 1000000000; i++)
        {
            Operation2();
        }
        sw1.Stop();
        Console.WriteLine(sw1.ElapsedMilliseconds);
        Console.Read();
    }

    static void Operation1()
    {
        if (ABoolean || (BBoolean && CBoolean))
        {
            AEnable = true;
            BEnable = true;
        }
        else
        {
            AEnable = false;
            BEnable = false;
        }
    }

    static void Operation2()
    {
        AEnable = (ABoolean || (BBoolean && CBoolean));
        BEnable = (ABoolean || (BBoolean && CBoolean));
    }
}

这导致在10亿次操作中差异大约8-9秒(第二种选择运行得更快).因为我添加了更多"启用"布尔值,但第二次操作变慢了.

Answer 1

不,我不希望编译器优化它.这有可能是JIT可以优化是(因为它有更多的信息),但我不希望C#编译器来.

编译器怎么知道是否SomeButton.Enabled会产生一些可能改变其价值的副作用ABoolean,BBoolean或者CBoolean？

编辑:验证这个...让我们给C#编译器绝对最大的机会:

class Test
{
    static void Main()
    {
        Foo(true, false, true);
    }

    static void Foo(bool x, bool y, bool z)
    {
        A = x || (y && z);
        B = x || (y && z);
    }

    static bool A { get; set; }
    static bool B { get; set; }
}

编译:

csc /o+ /debug- Test.cs

Foo通过ILDASM的代码:

.method private hidebysig static void  Foo(bool x,
                                           bool y,
                                           bool z) cil managed
{
  // Code size       37 (0x25)
  .maxstack  8
  IL_0000:  ldarg.0
  IL_0001:  brtrue.s   IL_000c
  IL_0003:  ldarg.1
  IL_0004:  brfalse.s  IL_0009
  IL_0006:  ldarg.2
  IL_0007:  br.s       IL_000d
  IL_0009:  ldc.i4.0
  IL_000a:  br.s       IL_000d
  IL_000c:  ldc.i4.1
  IL_000d:  call       void Test::set_A(bool)
  IL_0012:  ldarg.0
  IL_0013:  brtrue.s   IL_001e
  IL_0015:  ldarg.1
  IL_0016:  brfalse.s  IL_001b
  IL_0018:  ldarg.2
  IL_0019:  br.s       IL_001f
  IL_001b:  ldc.i4.0
  IL_001c:  br.s       IL_001f
  IL_001e:  ldc.i4.1
  IL_001f:  call       void Test::set_B(bool)
  IL_0024:  ret
} // end of method Test::Foo

如您所见,在两种情况下都会对表达式进行评估.