[llvm-dev] [cfe-dev] What version comes after 3.9? (Was: [3.9 Release] Release plan and call for testers)

Chris Lattner via llvm-dev llvm-dev at lists.llvm.org
Sat Jun 18 21:20:19 PDT 2016

> On Jun 18, 2016, at 9:16 PM, Chris Lattner via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> On Jun 14, 2016, at 1:32 AM, Richard Smith via cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote:
>> I think that this is the right approach, and we happen to have a natural forcing function here: opaque pointer types. I think we should increment the major version number when opaque pointer types are here, as it will be a major breaking change, and then we'll have a version 4.0. Until then, unless something else breaking comes up, 3.10 sounds fine to me.
>> We're talking about version numbers for the entire LLVM project here, which encompasses a lot more than LLVM IR, and for many parts of which LLVM IR is utterly irrelevant. I'm not convinced that tying version numbers to backwards-incompatible changes to IR is reasonable any more, and it doesn't seem hard to explicitly document the oldest version with which we are compatible (in fact, we need to do that regardless, whether we say it's "the same major version" or "everything since 3.0" or whatever else).
>> Given that our releases are time-based rather than feature-based, I don't see a distinct major / minor version being anything other than arbitrary, so I'd suggest we take 4.0 as our next release, 4.1 as the first patch release on that, 5.0 as the next release after that, and so on.
> I completely agree with Richard here.  “Breaking of IR compatibility” was an interesting metric for older and less mature versions of LLVM.  We can solve the same sort of challenge (the desire to eject old autoupgrade code) by having a sliding window of versions supported (e.g. version 4.5 supports back to version 3.6).

Let me clarify.  What I’m trying to say is that:

a) LLVM has a time-based release cycle, not a schedule-based one.  As such, a simple and predictable version number makes sense.
b) The LLVM project as a whole is a lot bigger than LLVM IR, even given its centrality to the project in some ways.
c) I think that it makes sense to keep adding 0.1 to each major release going forward well into the future.

On the topic of the pointer changes proposed, I really don’t think the community is served by waiting for that.  The supposition seems to be that we’d land it *without* upgrade support, but then bump the major version number to indicate this.  If that’s the proposal, I think that doing such a thing would be disastrous for the LLVM community as a whole: we need to have at least some sliding window of support for older formats.


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