This is slightly problematic. What if we have a wonderful SIMD-enabled
vector library that we compile with -fllvm, and then use it in a program
that isn't compiled with -fllvm, and some of the wonderful SIMD-enabled
functions get inlined? Presumably we get a panic in the NCG.
Did we discuss this before? I have vague memories, but don't remember
what the outcome was.
Cheers,
Simon
On 12/09/13 03:10, Geoffrey Mainland wrote:
We support compiling some code with -fllvm and some not in the same
executable. Otherwise how could users of the Haskell Platform link their
-fllvm-compiled code with native-codegen-compiled libraries like base, etc.?
In other words, the LLVM and native back ends use the same calling
convention. With my SIMD work, they still use the same calling
conventions, but the native codegen can never generate code that uses
SIMD instructions.
Geoff
On 09/11/2013 10:03 PM, Johan Tibell wrote:
OK. But that doesn't create a problem for the code we output with the
LLVM backend, no? Or do we support compiling some code with -fllvm and
some not in the same executable?
On Wed, Sep 11, 2013 at 6:56 PM, Geoffrey Mainland
<mainl...@apeiron.net <mailto:mainl...@apeiron.net>> wrote:
We definitely have interop between the native codegen and the LLVM
back
end now. Otherwise anyone who wanted to use the LLVM back end
would have
to build GHC themselves. Interop means that users can install the
Haskell Platform and still use -fllvm when it makes a performance
difference.
Geoff
On 09/11/2013 07:59 PM, Johan Tibell wrote:
> Do nothing different than you're doing for 7.8, we can sort it out
> later. Just put a comment on the primops saying they're
LLVM-only. See
> e.g.
>
>
>
https://github.com/ghc/ghc/blob/master/compiler/prelude/primops.txt.pp#L181
>
> for an example how to add docs to primops.
>
> I don't think we need interop between the native and the LLVM
> backends. We don't have that now do we (i.e. they use different
> calling conventions).
>
>
>
> On Wed, Sep 11, 2013 at 4:51 PM, Geoffrey Mainland
> <mainl...@apeiron.net <mailto:mainl...@apeiron.net>
<mailto:mainl...@apeiron.net <mailto:mainl...@apeiron.net>>> wrote:
>
> On 09/11/2013 07:44 PM, Johan Tibell wrote:
> > On Wed, Sep 11, 2013 at 4:40 PM, Geoffrey Mainland
> <mainl...@apeiron.net <mailto:mainl...@apeiron.net>
<mailto:mainl...@apeiron.net <mailto:mainl...@apeiron.net>>> wrote:
> > > Do you mean we need a reasonable emulation of the SIMD
primops for
> > > the native codegen?
> >
> > Yes. Reasonable in the sense that it computes the right
result.
> I can
> > see that some code might still want to #ifdef (if the
fallback isn't
> > fast enough).
>
> Two implications of this requirement:
>
> 1) There will not be SIMD in 7.8. I just don't have the
time. In fact,
> what SIMD support is there already will have to be removed if we
> cannot
> live with LLVM-only SIMD primops.
>
> 2) If we also require interop between the LLVM back-end and
the native
> codegen, then we cannot pass any SIMD vectors in
registers---they all
> must be passed on the stack.
>
> My plan, as discussed with Simon PJ, is to not support SIMD
primops at
> all with the native codegen. If there is a strong feeling that
> this *is
> not* the way to go, the I need to know ASAP.
>
> Geoff
>
>
>
_______________________________________________
ghc-devs mailing list
ghc-devs@haskell.org
http://www.haskell.org/mailman/listinfo/ghc-devs
