[LLVMdev] Calling-convention lowering proposal

Tanya M. Lattner tonic at nondot.org
Wed Apr 29 15:01:44 PDT 2009

>> Attached is a patch which significantly reworks how calls, incoming
>> arguments, and outgoing return values are lowered. It's a major change,
>> affecting all targets, so I'm looking for feedback on the approach.
> I don't have specific feedback on this patch but I do have feedback about how
> we go about making these kinds of changing.
> This patch changes the LLVM API.  We should have a process for deprecating
> obsolete interfaces before removing them entirely.  It's a significant
> maintenance headache to pull down a new release and fix all of the API
> issues along with tracking down new bugs introduced.
> I completely agree with the goals of this patch.  However, I would ask that we
> deprecate the existing interfaces for 2.6 and then remove them in 2.7.  We
> should add the new interfaces under a different name until 2.7 at which point
> they will become default.

I don't really see how this is any different. Instead of changing the API 
in 2.6, it just gets postponed to 2.7. So with 2.7 you have to upgrade 
your API and track down new bugs introduced by 2.7 (hopefully not very 

The majority of the people are not going to make the API changes until 
they are forced to. Its just low on the priority list. We've seen this 
from many people who don't upgrade because they don't want to make the API 


> LLVM is getting significant 3rd-party use and we should figure out how to act
> in a new way to better support our users.
>                                                    -Dave
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