llvm dev - Feb 2016 - distinguish program and temporary variables

Hi,

I need to check if a variable belongs to the program originally. Consider
the following code line:

y = x + 4

and its corresponding llvm ir (roughly):

%16 = load i32 %x
%add = add i32 %16, i32 4
store i32 %add, %y

I need to distinguish between %16, %add and %x, %y.

Any help is appreciated.

Best,
Mohammad
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On 2/8/16 9:39 AM, Mohammad Norouzi via llvm-dev wrote:
> Hi,
>
> I need to check if a variable belongs to the program originally. 
> Consider the following code line:
>
> y = x + 4
>
> and its corresponding llvm ir (roughly):
>
> %16 = load i32 %x
> %add = add i32 %16, i32 4
> store i32 %add, %y
>
> I need to distinguish between %16, %add and %x, %y.
You might be able to use the Debug information embedded within the LLVM 
IR to determine what is an original variable and what is a temporary 
added by LLVM.  However, I think that such an approach is fragile.

It sounds like you need to be analyzing Clang ASTs instead of LLVM IR.  
The Clang AST represents a program in its original source form, so you 
can tell what is a program variable, in what file it was defined, its 
original source type, etc.

Regards,

John Criswell
>
> Any help is appreciated.
>
> Best,
> Mohammad
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell

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> Hi,
>
> I need to check if a variable belongs to the program originally. Consider
> the following code line:
>
> y = x + 4
>
> and its corresponding llvm ir (roughly):
>
> %16 = load i32 %x
> %add = add i32 %16, i32 4
> store i32 %add, %y
>
> I need to distinguish between %16, %add and %x, %y.
>
>
> You might be able to use the Debug information embedded within the LLVM IR
> to determine what is an original variable and what is a temporary added by
> LLVM.  However, I think that such an approach is fragile.
>
yes, Debug info provides lots of useful info and i think there should be
sth about this case. But I don't know which api or method does this.

>
> It sounds like you need to be analyzing Clang ASTs instead of LLVM IR.
> The Clang AST represents a program in its original source form, so you can
> tell what is a program variable, in what file it was defined, its original
> source type, etc.
>
I'm not sure about Clang ASTs but this is part of an llvm pass which
analyzes llvm IR. So, i doubt if i can use Clang AST.

Best,
Mohammad

>
> Regards,
>
> John Criswell
>
>
> Any help is appreciated.
>
> Best,
> Mohammad
>
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
> --
> John Criswell
> Assistant Professor
> Department of Computer Science, University of
Rochesterhttp://www.cs.rochester.edu/u/criswell
>
>
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> On Feb 8, 2016, at 6:39 AM, Mohammad Norouzi via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> I need to check if a variable belongs to the program originally. Consider
the following code line:
> 
> y = x + 4
> 
> and its corresponding llvm ir (roughly):
> 
> %16 = load i32 %x
> %add = add i32 %16, i32 4
> store i32 %add, %y
> 
> I need to distinguish between %16, %add and %x, %y. 

This look like it will quickly degrades with optimization to a point where it
won't be meaningful.
Why are you needing this? What are you trying to accomplish?

-- 
Mehdi

I'm writing a pass that eliminates some variables. To show the effect of
the pass i need to show that I deleted the variables that originally appear
in the user code, not temporary variables added by llvm.

On Mon, Feb 8, 2016 at 5:59 PM, Mehdi Amini <mehdi.amini at apple.com>
wrote:
>
> > On Feb 8, 2016, at 6:39 AM, Mohammad Norouzi via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > Hi,
> >
> > I need to check if a variable belongs to the program originally.
> Consider the following code line:
> >
> > y = x + 4
> >
> > and its corresponding llvm ir (roughly):
> >
> > %16 = load i32 %x
> > %add = add i32 %16, i32 4
> > store i32 %add, %y
> >
> > I need to distinguish between %16, %add and %x, %y.
>
>
> This look like it will quickly degrades with optimization to a point where
> it won't be meaningful.
> Why are you needing this? What are you trying to accomplish?
>
> --
> Mehdi
>
>
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