[LLVMdev] Out-of-tree passes (Was: LLVM Weekly - #43, Oct 27th 2014)
listmail at philipreames.com
Mon Oct 27 09:41:25 PDT 2014
On 10/27/2014 08:46 AM, David Blaikie wrote:
> On Mon, Oct 27, 2014 at 2:59 AM, David Chisnall
> <David.Chisnall at cl.cam.ac.uk <mailto:David.Chisnall at cl.cam.ac.uk>> wrote:
> On 27 Oct 2014, at 09:33, Alex Bradbury <asb at asbradbury.org
> <mailto:asb at asbradbury.org>> wrote:
> > The Haskell community have put together a [proposal for an
> improved LLVM
> > backend to
> > They intend to ship GHC with its own local LLVM build.
> This post brings up an interesting point:
> > However, the framework is modular - we can extend LLVM with
> plugins. For example, several years ago, Max Bolingbroke wrote a
> plugin for LLVM's alias analysis that improved the generated code
> in some cases by 12%, just by teaching it GHC-specific code
> generation needs.
> > However, due to lack of API guarantees mentioned above, it
> becomes difficult to support such analysis for arbitrary end
> users, and we cannot fix or tune analysis results to specific
> versions of LLVM or GHC.
> This is a problem for anyone with an out-of-tree LLVM front end,
> or library, that would benefit from some custom optimisations.
> Without even a nod towards API (let alone ABI) stability for the
> core IR classes, it's very hard for people to gain the full
> benefit of using LLVM, unless their code is part of the LLVM tree
> and follows the same release cycle as LLVM (which doesn't scale).
> I don't know that many of the major contributors follow the LLVM
> release cycle, fwiw - one of the reasons we all care about stability
> on ToT so very much.
+1 on this. I use Clang on the release schedule, but our LLVM work
tracks TOT. IMHO, trying to do anything else for an embedded compiler
in a VM is pure folly and will lead to worlds of pain.
> (& at least Apple likely has lots of fun internal toys and they manage
> to follow ToT pretty closely, not sure about other major contributors
> - kind of the nature of many groups who keep their work out of ToT is
> that they're not involved in the community)
> - David
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
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