[PATCH] D34874: [ArgPromotion] Remove llvm.dbg.value on removed argument

[David Blaikie via llvm-commits]

I suspect removing this isn't the right option - changing its value to
'undef' (as done in the other review you sent, for arguments that were
actually promoted/changed their type) is probably best.

Nothing's going to work perfectly here. The user's going to be confused by
the missing parameter, or the debuggers going to be confused when it tries
to call the function with this parameter & it doesn't match the ABI
anymore, etc... - I don't think there's a good answer at the moment.

On Fri, Jun 30, 2017 at 8:27 AM Reid Kleckner via Phabricator via
llvm-commits <llvm-commits at lists.llvm.org> wrote:

> rnk added inline comments.
>
>
> ================
> Comment at: lib/Transforms/IPO/ArgumentPromotion.cpp:135
> +
> +      BasicBlock &BB = F->getEntryBlock();
> +      SmallVector<Instruction*, 8> InstrsToRemove;
> ----------------
> There's no reason to believe the only uses of the argument will appear in
> the entry block. I think you really want to do
> `I->replaceAllUsesWith(undef)` to replace all metadata uses of the
> argument. Some other pass (instcombine?) can clean up the useless dbg.value
> instructions. That's what the dead argument elimination pass does, anyway.
>
>
> https://reviews.llvm.org/D34874
>
>
>
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