[PATCH] Make discardable symbols externally visible to prevent discarding in llvm-extract.

[Lang Hames]

An alternative fix for this would be modifying the ExtractGV pass directly.
At present it checks "hasLocalLinkage" when deciding whether to bump the
linkage type. I think it should be checking isDiscardableIfUnused()
instead. Alternate patch attached.

- Lang.


On Sun, Mar 3, 2013 at 4:40 PM, Lang Hames <lhames at gmail.com> wrote:

> Hi All,
>
> llvm-extract has tricked me a couple of times by handing me back an empty
> module when I asked it to extract a linkonce function. The problem is that
> when DCE tidies up the module, it strips out the function that you wanted
> to extract.
>
> To avoid that problem, this patch sets the linkage on any function that
> was requested on the command line, and that would be discarded by DCE, to
> ExternalLinkage.
>
> Given the use cases that I'm aware of for llvm-extract I think this should
> be an improvement. It certainly seems better than handing back an empty
> module. If anybody is concerned about this quietly changing the linkage
> type then I can improve the patch to restore the original linkage types
> after DCE is run.
>
> Cheers,
> Lang.
>
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