Eliding of slice range checking

[Per Nordlöw]

Does DMD/LDC avoid range-checking in slice-expressions such as 
the one in my array-overload of `startsWith` defined as

bool startsWith(T)(scope const(T)[] haystack,
                    scope const(T)[] needle)
{
     if (haystack.length >= needle.length)
     {
         return haystack[0 .. needle.length] == needle; // is 
slice range checking avoid here?
     }
     return false;
}

///
@safe pure nothrow @nogc unittest
{
     auto x = "beta version";
     assert(x.startsWith("beta"));
}

when building in release mode?

I remember a DMD pull from Ian Buclaw that enabled some eliding 
but I don't remember if it includes the case above.

How can I investigate the codegen myself here?