[LLVMdev] [RFC] Module Flags Metadata

[Devang Patel]

On Jan 27, 2012, at 5:00 PM, Dan Gohman wrote:

> Not all of these are miscompiles,

None I'd say, may be TBAA.

> but the point is that valid but
> naive optimizations can cause them to be actively misleading 

... but not cause mis-compilation. Note, optimization passes are free to update info conveyed through MDNodes, if they want to. The "optional to update" while still preserving _correctness_ of the program is a key property of MDNodes.

Regarding, TBAA you say that this optionality is not optional. If you insist that all transformation passes in pipeline _must_ ensure correctness of alias info conveyed by front end as part of TBAA then I guess you need an explicit mechanism anyway. In that case, I'd encourage you to develop a representation that meets needs instead of twisting MDNodes. In other words, I'd not support direction where all transformation passes are _required_ to preserve semantics of any information encoded through MDNodes. That's all.
-
Devang

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