NAOT: isinst with multiple guesses without fallback #97602
Description
interface IMyInterface { }
public class MyImplementation1 : IMyInterface { }
public class MyImplementation2 : IMyInterface { }
class Program
{
static void Main()
{
Test(new MyImplementation1());
Test(new MyImplementation2());
}
[MethodImpl(MethodImplOptions.NoInlining)]
static void Test(object o)
{
if (o is IMyInterface)
Console.WriteLine("MyInterface!");
}
}Since there are only 2 classes implementing IMyInterface, JIT should be able to optimize Test as follows:
if (o != null && ((o.GetType() == typeof(MyImplementation1) || o.GetType() == typeof(MyImplementation2))
{
}without any helper call fallback. Similar to what NAOT already does for virtual calls.
Current codegen for Test:
; Assembly listing for method Program:Test(System.Object) (FullOpts)
sub rsp, 40
mov rdx, rcx
lea rcx, [(reloc 0x4000000000422460)] ; IMyInterface
call CORINFO_HELP_ISINSTANCEOFINTERFACE
test rax, rax
je SHORT G_M3485_IG04
lea rcx, gword ptr [(reloc 0x4000000000422478)] ; '"MyInterface!"'
call System.Console:WriteLine(System.String)
G_M3485_IG04:
nop
add rsp, 40
ret
; Total bytes of code 42Expected codegen:
; Assembly listing for method Program:Test(System.Object) (FullOpts)
sub rsp, 40
test rcx, rcx
je SHORT G_M3485_IG05
mov rcx, qword ptr [rcx]
lea rax, [(reloc 0x40000000004224f8)] ; MyImplementation1
cmp rcx, rax
je SHORT G_M3485_IG04
lea rax, [(reloc 0x4000000000422518)] ; MyImplementation2
cmp rcx, rax
jne SHORT G_M3485_IG05
G_M3485_IG04:
lea rcx, gword ptr [(reloc 0x4000000000422520)] ; '"MyInterface!"'
call System.Console:WriteLine(System.String)
G_M3485_IG05:
nop
add rsp, 40
ret
; Total bytes of code 54