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Re: [DotGNU]callvirt change to cscc

From: Rhys Weatherley
Subject: Re: [DotGNU]callvirt change to cscc
Date: Fri, 15 Nov 2002 21:06:41 +1000

Gopal V wrote:

> this totally destroys the efficency of using non-virtual methods ...
> Because if we're going to lookup each and every method .... It's just
> one lookup per method for every call . IMHO we should try to optimise
> rather than correct non-existent bugs for non-existent compatibility..

Actually, the runtime impact isn't as big as you think.  The verifier
notices that "callvirt" is being used on a non-virtual method and
inserts a normal CVM "call" opcode, rather than CVM's "call_virtual".
The only runtime change is to do a "cknull" before the "call".
It doesn't have to do a virtual method lookup for every call - it
can call the destination method directly.

> The correct NullReferenceException will be thrown when the called
> method accesses 'this' anyway...
> Sorry, I don't like this change ... This is neither good or bad ..
> it's UGLY ...

I agree with you.  Unfortunately, compatibility trumps efficiency
in this case.  Under MS'es compiler/runtime, the following throws
a NullReferenceException even though "this" is never touched by
the "DoNothing" method:

    using System;

    public class Test
        public void DoNothing()

        public static void Main()



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