llvm dev - Nov 2009 - [LLVMdev] extracting data and operands

Hi,

I wish to implement dead code elimination as a pass in llvm. This is not the
same as unreachable block.
For this, I plan to go ahead like this :
In each function
    Identify the store and branch operations
    Identify the operands involved in these operations.
    Build the UD chain of these and check if there is any variable that is
not used and mark its definition (the entire instruction)
Delete all marked instructions.

I have no clue how to do this using llvm. Any help would be greatly
appreciated.

Regards,
Hersh


-- 
HSIyer
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Hersh,

On Mon, Nov 16, 2009 at 11:25 AM, Hersh.S. Iyer <coolhersh at gmail.com>
wrote:
> Hi,
>
> I wish to implement dead code elimination as a pass in llvm. This is not
the
> same as unreachable block.
> For this, I plan to go ahead like this :
> In each function
>     Identify the store and branch operations
>     Identify the operands involved in these operations.
>     Build the UD chain of these and check if there is any variable that is
> not used and mark its definition (the entire instruction)
> Delete all marked instructions.
>
> I have no clue how to do this using llvm. Any help would be greatly
> appreciated.
>
Read  lib/Transforms/Scalar/DCE.html. It'll help you understand how to
write such transformations in LLVM.
-
Devang