c# - 'unsafe' 作用域的嵌套会影响性能吗？

Question

我想问一下第一个例子是否比第二个例子慢。

例子1:for, unsafe, unsafe, unsafe, etc

for (var i = 0; i < ...; i++)
{
    unsafe
    {
        // ...
    }
}

示例 2:不安全，对于

unsafe
{
    for (var i = 0; i < ...; i++)
    {
        // ...
    }
}

无处in the documentation这方面正在被涵盖。

问题:

有人可以假设 unsafe 代码块的位置不会影响性能吗？

Answer 1

它们生成完全相同的 IL 代码，因此没有性能差异

嵌套: See on SharpLab

c#

using System;
public class C {
    public void M() {
        var x = 0;
        for (var i = 0; i < 100; i++)
        {            
            unsafe { x+=i; }
        }
    }
}

IL

.class private auto ansi '<Module>'
{
} // end of class <Module>

.class public auto ansi beforefieldinit C
    extends [System.Private.CoreLib]System.Object
{
    // Methods
    .method public hidebysig 
        instance void M () cil managed 
    {
        // Method begins at RVA 0x2050
        // Code size 20 (0x14)
        .maxstack 2
        .locals init (
            [0] int32,
            [1] int32
        )

        IL_0000: ldc.i4.0
        IL_0001: stloc.0
        IL_0002: ldc.i4.0
        IL_0003: stloc.1
        // sequence point: hidden
        IL_0004: br.s IL_000e
        // loop start (head: IL_000e)
            IL_0006: ldloc.0
            IL_0007: ldloc.1
            IL_0008: add
            IL_0009: stloc.0
            IL_000a: ldloc.1
            IL_000b: ldc.i4.1
            IL_000c: add
            IL_000d: stloc.1

            IL_000e: ldloc.1
            IL_000f: ldc.i4.s 100
            IL_0011: blt.s IL_0006
        // end loop

        IL_0013: ret
    } // end of method C::M

    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        // Method begins at RVA 0x2070
        // Code size 7 (0x7)
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [System.Private.CoreLib]System.Object::.ctor()
        IL_0006: ret
    } // end of method C::.ctor

} // end of class C

周边: See on SharpLab

c#

using System;
public class C {
    public void M() {
        var x = 0;
        unsafe {
            for (var i = 0; i < 100; i++)
            {            
                x+=i;
            }
        }
    }
}

IL

.class private auto ansi '<Module>'
{
} // end of class <Module>

.class public auto ansi beforefieldinit C
    extends [System.Private.CoreLib]System.Object
{
    // Methods
    .method public hidebysig 
        instance void M () cil managed 
    {
        // Method begins at RVA 0x2050
        // Code size 20 (0x14)
        .maxstack 2
        .locals init (
            [0] int32,
            [1] int32
        )

        IL_0000: ldc.i4.0
        IL_0001: stloc.0
        IL_0002: ldc.i4.0
        IL_0003: stloc.1
        // sequence point: hidden
        IL_0004: br.s IL_000e
        // loop start (head: IL_000e)
            IL_0006: ldloc.0
            IL_0007: ldloc.1
            IL_0008: add
            IL_0009: stloc.0
            IL_000a: ldloc.1
            IL_000b: ldc.i4.1
            IL_000c: add
            IL_000d: stloc.1

            IL_000e: ldloc.1
            IL_000f: ldc.i4.s 100
            IL_0011: blt.s IL_0006
        // end loop

        IL_0013: ret
    } // end of method C::M

    .method public hidebysig specialname rtspecialname 
        instance void .ctor () cil managed 
    {
        // Method begins at RVA 0x2070
        // Code size 7 (0x7)
        .maxstack 8

        IL_0000: ldarg.0
        IL_0001: call instance void [System.Private.CoreLib]System.Object::.ctor()
        IL_0006: ret
    } // end of method C::.ctor

} // end of class C