[Mesa-dev] 761131ce4591e5f55f38d13f2c4d2194bc9cb0fd build regression with llvm 2.8

[Will Schmidt]

On Thu, 2012-07-26 at 07:52 -0700, Jose Fonseca wrote:
> ----- Original Message -----
> > On 7/21/12 5:53 AM, Jose Fonseca wrote:
> > > ----- Original Message -----
> > >> Hi guys
> > >>
> > >> LLVM 2.8 doesn't appear to have mcjit, so we end up with no llvm
> > >> libs
> > >> defined,
> > >
> > > Yes, mcjit is only used/necessary from llvm-3.1 onwards, so the
> > > autoconf code should check conditiionally.
> > >
> > > BTW, I'll soon commit a change that will stop using mcjit from 3.2
> > > onwards (as with the current LLVM 3.2 trunk, AVX is supported by
> > > the old jit, which is more stable/polished).

Can you clarify the scope of "will stop using mcjit from 3.2 onwards"?
Is that specific to (the Intel AVX extensions?) related matters, or is
that a mesa-wide statement?    (I am specifically interested in the
llvmpipe related parts that Adam touched on below).

Thanks, 
-Will

> > 
> > Is there a long-term plan or theory for which jit we'll be using?
> >  Are we just following upstream?  
> 
> I see ourselves foremost as consumers of LLVM, so the default answer is: to follow upstream, unless it does not fit our purposes.
> 
> > Are the problems of mcjit simply a superset
> > of the problems with the old jit?
> 
> The only reason we started to look at mcjit was because old jit didn't support avx. But on current trunk (ie llvm-3.2) it does.
> 
> To be honest, apart of avx, none of the benefits of mcjit matter to me:
> - we're not compiling from a C source file (or any kind of source file), so not sure what GDB integration will bring
> and all its shortcomings affect me
> - each engine can only compile one module -- huge memory waste
> - there are redundant version of the code -- more memory waste
> - half baked ELF support
> - does not support windows
> 
> IMO, mcjit it's not production quality, and progress has been awfully slow.
> 
> > I know there are people interested in supporting other arches in
> > llvmpipe, so it'd be nice if they knew what to work on.  And
> > personally
> > the gdb integration bit of mcjit sounds really appealing from a
> > support
> > perspective.
> 
> llvmpipe currently can support both, so it's really their choice.
> 
> Jose
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