[LLVMdev] datalayout optimization question

[Jim Grosbach]

Are you expecting to use a single set of IR files to generate code for multiple targets? Otherwise I'm not sure why your .ll files would necessarily lack the data layout information. The reason I ask is that LLVM IR is fundamentally not target independent in ways far beyond the presence or absence of the data layout string.

For gory details: http://lists.cs.uiuc.edu/pipermail/llvmdev/2011-October/043719.html.

Beyond that, rather large, caveat, I'm not sure of the answer to your specific question. It's not so much which optimizations are turned off, per se, but rather that some won't have the information they need (alignment data, for example) to do a good job, so they'll miss opportunities.

Regards,
  Jim

On Apr 16, 2012, at 9:06 AM, Sebastien DELDON-GNB <sebastien.deldon at st.com> wrote:

> Hi all,
>  
> We are developing our own compiler front-end and use LLVM as back-end. We generate .ll files and use opt/llc to generate target specific code. When I generate datalayout information in my .ll file it seems that it enables more optimization from LLVM opt. How can I determine which optimization are driven by datalayout information generation ?
> In other words, when I don’t generate target specific datalayout information, what are the optimizations that are turned off ?
>  
> Thanks for answers
> Best Regards
> Seb
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