static bool Test(int x) => (x & 1) == 0;

Just a good first issue for anyone interested in contributing to CLR JIT.

Current codegen:

test     cl, 1
sete     al
movzx    rax, al
ret

Expected codegen:

mov      eax, ecx
and      eax, 1
ret

I noticed it when I was trying to implement a faster IsNegative for floats:

static bool IsNegative(double x) => 
    (Sse2.MoveMask(Vector128.CreateScalarUnsafe(x)) & 1) != 0;