[LLVMdev] [proposal] Extensible IR metadata
clattner at apple.com
Fri Sep 11 17:22:51 PDT 2009
On Sep 11, 2009, at 3:23 PM, David Greene wrote:
> I have a few questions and comments about Chris' initial proposal as
> - I don't like the separation between "built-in" metadata and
> metadata. Why not make all metadata use the RegisterMDKind
> interface and
> just have the LLVM libraries do it automatically for the "built-in"
> Having a separate namespace of enums is going to get confusing.
> every day I curse the fact that "int" is different than "MyInt" in C
> ++. :-/
"builtin" metadata would also be registered, the only magic would be
that the encoding would be smaller in the IR.
> - Defaulting alignment to 1 when metatadata is not present is going
> to be a
> huge performance hit on many architectures. I hope we can find a
> solution. I'm not sure what it is yet because we have to maintain
> I just fear a Pass inadvertantly dropping metadata and really
> things up.
I don't expect metadata to be commonly stripped. This could be just
as bad a perf problem for other things like TBAA or high level type
information for a dynamic language. I think it is important that the
IR is possible to reason about even in uncommon cases though.
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