llvm dev - Aug 2007 - [LLVMdev] constructing 'for' statement from LLVM bitcode

---- Original message ----
>Date: Fri, 24 Aug 2007 22:23:39 -0700
>From: Chris Lattner <sabre at nondot.org>  
>Subject: Re: [LLVMdev] constructing 'for' statement from LLVM
bitcode
>To: LLVM Developers Mailing List <llvmdev at cs.uiuc.edu>
>
>
>On Aug 24, 2007, at 10:07 PM, Seung Jae Lee wrote:
>
>> Do you have any idea on how I can construct 'for' more
systemically
>> with this CDG info from LLVM bitcode?
>>
>
>I strongly suggest looking at the Muchnick book: http:// 
>www.amazon.com/Advanced-Compiler-Design-Implementation-Muchnick/dp/ 
>1558603204
>
>It has a section on "structural analysis" that you will find
useful.
>
>Why do you want "for statements"?
>
Thank you for this info, Chris.
I'm doing this 'cause I'm making a backend for a virtual machine
assembly has an instruction which is very similar to 'for' statement.
I know this seems quite strange for that machine instruction looks quite
high-level.
Furthermore, it doesn't have instructions such as 'br' in LLVM so
this is why I have to re-construct 'for' statement for the assembly from
LLVM bitcode. (I must not use 'goto' in the high-level source code,
either. :-/)

Thanks,
SJL
>-Chris
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>> It has a section on "structural analysis" that you will find
useful.
>>
>> Why do you want "for statements"?
>>
>
> Thank you for this info, Chris.
> I'm doing this 'cause I'm making a backend for a virtual
machine
> assembly has an instruction which is very similar to 'for'
statement.
> I know this seems quite strange for that machine instruction looks  
> quite high-level.
> Furthermore, it doesn't have instructions such as 'br' in LLVM
so
> this is why I have to re-construct 'for' statement for the assembly
> from LLVM bitcode. (I must not use 'goto' in the high-level source
> code, either. :-/)
Ok.  Note that LLVM can represent irreducible loops.  You can handle  
this through code duplication.

-Chris

Seung,

On 8/25/07, Chris Lattner <sabre at nondot.org>
wrote:
> Ok.  Note that LLVM can represent irreducible loops.  You can handle
> this through code duplication.
> -Chris

If you are willing to invest more effort into a more complicated analysis,
in many cases you can even avoid code duplication. See this paper for
details:

@inproceedings{erosa94taming,
  author    = {Ana M. Erosa and
               Laurie J. Hendren},
  title     = {Taming Control Flow: A Structured Approach to Eliminating
               Goto Statements.},
  booktitle = {ICCL},
  year      = {1994},
  pages     = {229--240},
 }

Cheers,

-- 
        Domagoj Babic

        http://www.domagoj.info/
        http://www.calysto.org/