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

[Will Schmidt]

On Thu, 2012-07-26 at 10:31 -0700, Jose Fonseca wrote:
> ----- Original Message -----
> > 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"?
> 
> What I meant by that was already done in commit c30bf68946433d26f672c741a763bba4712aada7.

> > 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).
> 
> The MC-JIT vs old JIT is currently a build time choice (based on
> #ifdef's). Essentially, we only use MC-JIT for LLVM 3.1, if AVX
> support hasn't been backported (ie. when not using my backports_31
> branch below).

Ok.  Between the explanation and the commit you mentioned above, it's
clearer now.  Thanks. :-)    Additional comment below.

> It could be made into a runtime choice if you prefer, ie., based of
> the availability of AVX. Or we could just disable MC-JIT altogether,
> and wait until it replaces the old jit upstream.

Per the "Help with PPC64 JIT" comments on llvm-dev last week, we are
currently working on MC-JIT, rather than oldJIT (This ultimately in
support of mesa/llvmpipe functionality on ppc64).   Some of the work is
occurring with fedora17 based sources, but most on Trunk/HEAD.  (so
HAVE_LLVM == 0x0302 ).

So would prefer some way to specify that MC-JIT be used.  A run-time (or
easy build-time configure option) choice would be nice.

Thanks, 
-Will

> 
> BTW, for best results using llvmpipe on 3.1, please consider using
> http://cgit.freedesktop.org/~jrfonseca/llvm/log/?h=backports_31 as it
> includes some backports of bugs/enhacements that affect llvmpipe to
> LLVM 3.1.
> 
> Jose
>