MSIL Optimizer?

[cody]

is there any tool which can optimize msil? for example:

if (a is MyType)
{
MyType mt = (MyType)a
}

could turn into:

MyType mt = mt as MyType ;
if (mt!=null)
{
}

Maybe there are much more such situations.

I know that the jitter *could* do such Optimisations, but does it?

--
cody

Freeware Tools, Games and Humour
http://www.deutronium.de.vu || http://www.deutronium.tk

[Josip Medved]

Re: MSIL Optimizer?

> is there any tool which can optimize msil? for example:[color=blue]
> if (a is MyType)
> {
> MyType mt = (MyType)a
> }
> could turn into:
> MyType mt = mt as MyType ;
> if (mt!=null)
> {
> }
> Maybe there are much more such situations.[/color]

yes... same tool that can make ugly woman beautiful... :)
there is no optimizer for poorly written code...

--

Pozdrav,
Josip Medved, MCSD

http://www.jmedved.com

[cody]

Re: MSIL Optimizer?

> > is there any tool which can optimize msil? for example:[color=blue][color=green]
> > if (a is MyType)
> > {
> > MyType mt = (MyType)a
> > }
> > could turn into:
> > MyType mt = mt as MyType ;
> > if (mt!=null)
> > {
> > }
> > Maybe there are much more such situations.[/color]
>
> yes... same tool that can make ugly woman beautiful... :)
> there is no optimizer for poorly written code...[/color]


1. this is no poorly written code
2. it would simply be possible to make such a tool
3. the question is: does such a tool exist?

--
cody

Freeware Tools, Games and Humour
http://www.deutronium.de.vu || http://www.deutronium.tk

[Miha Markic [MVP C#]]

Re: MSIL Optimizer?

> 1. this is no poorly written code[color=blue]
> 2. it would simply be possible to make such a tool[/color]

Really?


--
Miha Markic [MVP C#] - RightHand .NET consulting & development
miha at rthand com

https://www.rthand.com

[Jon Skeet [C# MVP]]

Re: MSIL Optimizer?

<"Miha Markic [MVP C#]" <miha at rthand com>> wrote:[color=blue][color=green]
> > 1. this is no poorly written code
> > 2. it would simply be possible to make such a tool[/color]
>
> Really?[/color]

I suspect it wouldn't be *very* hard to write something which detected
the code that the C# compiler emitted for

if (localVariable is SomeType)
{
anyVariable = (SomeType)local Variable;
}

and converted it to the appropriate "as" form.

(Whether or not it should deal with non-local variables is a slightly
different matter - it would depend on the volatility of the variable,
for a start.)

Whether or not it would be worth it would be an entirely different
matter. Possibly the C# compiler could be tweaked to optimise the code
itself at that stage - or emit a warning to suggest the more optimal
code?

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Justin Rogers]

Re: MSIL Optimizer?

Truthfully the only thing that needs to be IL optimized at this stage of the C#
compiler is stack local usage. They don't share stack locals for nested
elements, when they probably should, since IL has a method for aliasing
nested locals to be re-used. For instance:

for(int i = 0; i < 10; i++) {}
for(int i = 0; i < 10; i++) {}
for(int i = 0; i < 10; i++) {}

How many locals does that produce? 3 of them, though you'd only think
it would produce one. IL has something called slot aliasing, so they could
refer to i as V_0, V_1, and V_2, but all three of these variables would
share the same stack slot.

This is only a code-size enhancement, but it produces decent results. As for
the 'as' enhancement. That type of layout is easy to detect. Changing it
really
doesn't produce that much of an enhancement though, and you'd have to
special case your detection logic so that it didn't try to convert value type
instances of the is/casting pattern. Of course, the IL for a value type versus
object type casting looks different (castclass versus unbox), so that shouldn't
be a big issue.

I can't find my blog entry on the stack local enhancement, but it is in there
somewhere
under the performance category if anyone is interested.

--
Justin Rogers
DigiTec Web Consultants, LLC.
Blog: http://weblogs.asp.net/justin_rogers



"Jon Skeet [C# MVP]" <skeet@pobox.co m> wrote in message
news:MPG.1b01f4 732cd6a0c298a83 8@msnews.micros oft.com...[color=blue]
> <"Miha Markic [MVP C#]" <miha at rthand com>> wrote:[color=green][color=darkred]
> > > 1. this is no poorly written code
> > > 2. it would simply be possible to make such a tool[/color]
> >
> > Really?[/color]
>
> I suspect it wouldn't be *very* hard to write something which detected
> the code that the C# compiler emitted for
>
> if (localVariable is SomeType)
> {
> anyVariable = (SomeType)local Variable;
> }
>
> and converted it to the appropriate "as" form.
>
> (Whether or not it should deal with non-local variables is a slightly
> different matter - it would depend on the volatility of the variable,
> for a start.)
>
> Whether or not it would be worth it would be an entirely different
> matter. Possibly the C# compiler could be tweaked to optimise the code
> itself at that stage - or emit a warning to suggest the more optimal
> code?
>
> --
> Jon Skeet - <skeet@pobox.co m>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too[/color]

[Josip Medved]

Re: MSIL Optimizer?

> I suspect it wouldn't be *very* hard to write something which detected[color=blue]
> the code that the C# compiler emitted for[/color]
[color=blue]
> if (localVariable is SomeType)
> {
> anyVariable = (SomeType)local Variable;
> }[/color]
[color=blue]
> and converted it to the appropriate "as" form.[/color]


really?
that means that compiler should check every possible path
of actions in program to ensure that this IS a form... when
someone uses object like this, I presume that he will be
using different objects and in that case optimization is in
*very-almost imposible* hard.

--

Pozdrav,
Josip Medved, MCSD

http://www.jmedved.com

All given above is stated IMHO.

[Jon Skeet [C# MVP]]

Re: MSIL Optimizer?

Josip Medved <jmedved@jmedve d.com> wrote:[color=blue][color=green]
> > I suspect it wouldn't be *very* hard to write something which detected
> > the code that the C# compiler emitted for[/color]
>[color=green]
> > if (localVariable is SomeType)
> > {
> > anyVariable = (SomeType)local Variable;
> > }[/color]
>[color=green]
> > and converted it to the appropriate "as" form.[/color]
>
> really?
> that means that compiler should check every possible path
> of actions in program to ensure that this IS a form...[/color]

No, not at all.
[color=blue]
> when someone uses object like this, I presume that he will be
> using different objects and in that case optimization is in
> *very-almost imposible* hard.[/color]

It wouldn't need to test that at all. It would merely need to convert:

if (localVariable is SomeType)
{
anyVariable = (SomeType)local Variable;
}

into

SomeType tmp = localVariable as SomeType;
if (tmp != null)
{
anyVariable = tmp;
}

It doesn't need to keep track of anything other than other than
spotting the above pattern. It doesn't need to work out whether or not
the object is an instance of the given type - the "as" operator does
that instead, just more efficiently.

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too