llvm dev - Nov 2012 - [LLVMdev] LLVM Value relationship with metadata

Hello All,

Would anybody explain why there is not direct connection between llvm::Value
and metadata nodes. If llvm::Value hold pointer to its MDNode would it cause
any malfunctioning?

Thanks in advance,
Arsen



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On 5 Nov 2012, at 07:07, Arsen wrote:
> Would anybody explain why there is not direct connection between
llvm::Value
> and metadata nodes. If llvm::Value hold pointer to its MDNode would it
cause
> any malfunctioning?
The rationale was that most values did not have any metadata, and therefore
there would be a space penalty paid for every node.  Increasingly, it seems that
nodes have several metadata nodes and so they are all paying the time penalty
for the lookup.  It is probably worth doing some profiling to see what the costs
are.  At low optimisation levels, there is a lot of debug metadata.  At higher
ones, there is a lot of TBAA metadata.

David

Thanks for your reply David. Would you please clarify what do you mean by
saying:

David Chisnall-5 wrote
> Increasingly, it seems that nodes have several metadata nodes and so they
> are all paying the time penalty for the lookup. 
Arsen



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