[cfe-dev] Emitting loop metadata in codegen

[ihusar at fit.vutbr.cz]

Dear Paul and others,

   I would like to ask whether you made any progress with this,
we are actually trying to do a similar thing:

- One thing is to introduce ICC-like pragmas and add support for them in  
the vectorizer
   (in fact this seems like the thing you were doing).
- Second one is to identify a block of code that should be identified as an
   instruction set extension (ISE) and automatically generate a
   description for an ADL Codal used in Codasip Framework.

I successfully added some pragmas to the clang, but currently I am trying  
to figure out how to
correctly store metadata.

Do you have some clues i could follow? E.g. if the code is not private to  
Intel, could I take a look?:)

Thank you and best regards
   Adam




On Fri, 22 Feb 2013 21:50:57 +0100, Redmond, Paul <paul.redmond at intel.com>  
wrote:

> Hi,
>
> As discussed earlier I'm implementing #pragma ivdep in clang. I use  
> AttributedStmt with an IVDepAttr to wrap loop Stmts in the AST. So far I  
> have only hacked in codegen to attach loop metadata.
>
> To do this correctly I need to attach metadata to all predecessors of  
> the loop header. Also, I need to attach metadata to all loads and stores  
> in the loop. (see llvm.loop.parallel and llvm.mem.parallel_loop_access)
>
> I'm wondering what the best way to implement this in clang codegen? I  
> think this could get really messy and become very fragile if I just  
> start modifying EmitForStmt, etc to check for some flag.
>
> One idea I've been thinking about is creating the metadata after code  
> emission using a llvm loop pass (living in clang/lib/CodeGen) Basically  
> during codegen I would attach a simple metadata (clang.pragma.ivdep or  
> something) to a block in the loop and use the pass to translate to the  
> metadata understood by llvm. I don't see a precedent for running  
> clang-specific passes in codegen though..
>
> Comments and suggestions are appreciated.
>
> paul
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