[Llvm-bgq-discuss] Limitation in bgclang's QPX support

[Hal Finkel]

----- Original Message -----
> From: "Hal Finkel" <hfinkel at anl.gov>
> To: "Phil Miller" <mille121 at illinois.edu>
> Cc: llvm-bgq-discuss at lists.alcf.anl.gov
> Sent: Wednesday, May 14, 2014 5:18:55 PM
> Subject: Re: [Llvm-bgq-discuss] Limitation in bgclang's QPX support
> 
> Phil,
> 
> I'll look into this. There may be a way to enable the 'splat'
> behavior here. In the mean time, you can just write:
> vector4double fullvirial_v0 = (vector4double) { 0.0, 0.0, 0.0, 0.0 };

Also, you can use the vec_splats intrinsic on both compilers:

vector4double fullvirial_v0 = vec_splats(0.0);

 -Hal

> 
>  -Hal
> 
> ----- Original Message -----
> > From: "Phil Miller" <mille121 at illinois.edu>
> > To: llvm-bgq-discuss at lists.alcf.anl.gov
> > Sent: Wednesday, May 14, 2014 1:37:09 PM
> > Subject: [Llvm-bgq-discuss] Limitation in bgclang's QPX support
> > 
> > 
> > 
> > 
> > Aside from the optimization errors I recently reported, the only
> > other impediment to compiling unmodified NAMD with bgclang is a big
> > pile of errors of the following nature:
> > ====
> > error: C-style cast from 'double' to 'vector4double' is not allowed
> > vector4double fullvirial_v0 = (vector4double) (0.0);
> > ====
> > 
> > The desired semantics of statements like this are pretty
> > straightforward, and don't seem to conflict with anything else.
> > bgxlc is happy to accept these statements, so this can be viewed as
> > a (hopefully unintended) compatibility limitation.
> > 
> > 
> > 
> > If there's a more portable way to express this construct, I might
> > be
> > able to pass a patch up to the NAMD developers.
> > 
> > 
> > These were avoided by disabling the QPX-specialized code, and using
> > the portable C/C++ versions instead. So, I was finally able to
> > compile and link a NAMD binary using purely the bgclang toolchain.
> > If I encounter subsequent runtime trouble, I'll follow up with
> > another post.
> > 
> > _______________________________________________
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> > llvm-bgq-discuss at lists.alcf.anl.gov
> > https://lists.alcf.anl.gov/mailman/listinfo/llvm-bgq-discuss
> > 
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
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> llvm-bgq-discuss at lists.alcf.anl.gov
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> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory