I was discovering the IL code
of a simple program:
long x = 0;
for(long i = 0;i< int.MaxValue * 2L; i++)
{
x = i;
}
Console.WriteLine(x);
I build this code in Release mode and this IL code
is generated:
.method private hidebysig static void Main(string[] args) cil managed
{
.entrypoint
// Code size 28 (0x1c)
.maxstack 2
.locals init ([0] int64 x,
[1] int64 i)
IL_0000: ldc.i4.0
IL_0001: conv.i8
IL_0002: stloc.0
IL_0003: ldc.i4.0
IL_0004: conv.i8
IL_0005: stloc.1
IL_0006: br.s IL_000f
IL_0008: ldloc.1
IL_0009: stloc.0
IL_000a: ldloc.1
IL_000b: ldc.i4.1
IL_000c: conv.i8
IL_000d: add
IL_000e: stloc.1
IL_000f: ldloc.1
IL_0010: ldc.i4.s -2
IL_0012: conv.u8
IL_0013: blt.s IL_0008
IL_0015: ldloc.0
IL_0016: call void [mscorlib]System.Console::WriteLine(int64)
IL_001b: ret
} // end of method Program::Main
I figure out pretty much all the insructions except this:
IL_0010: ldc.i4.s -2
Now this insruction should push int.MaxValue * 2L
onto the stack and then blt.s
will compare it with i
, if i
is less than the value go back to the IL_0008
.But, what I can't figure out is that why it loads -2 ? If I change the loop like below:
for(long i = 0;i < int.MaxValue * 3L; i++)
{
x = i;
}
It loads the expected value:
IL_0010: ldc.i8 0x17ffffffd
So what is the meaning of -2
in this code?