[Llvm-bgq-discuss] bgclang r185769-20130706 on vesta/mira

[Hal Finkel]

----- Original Message -----
> 
> 
> 
> 
> 
> A small bugreport:
> 
> qpxintrin.h:658
> #define vec_sldw(a, b, c) __builtin_shufflevector(a, b, c, (c)+1,
> (c)+2, (c)+3);

Oops; thanks! I'll fix that shortly.

> 
> The semicolon at the end should be removed. It prohibites using this
> macro as a function argument.
> 
> (Why are some intrinsics defined as macros, but most as inline
> functions? I think vec_sldw should be converted to an inlined
> function, because otherwise c will be evaluated multiple times:
> vec_sldw(a, b, c++))

As I recall, I tried it and it did not work (because the compiler checks, at the semantic level, that the control argument is a constant). Maybe there is a better way?

 -Hal

> 
> 
> Kind regards,
> Michael Kruse
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 2013/7/14 Hal Finkel < hfinkel at anl.gov >
> 
> 
> Erik,
> 
> I've updated the installs on vesta/mira to fix this issue as well.
> First, the underlying problem was that structures that contain a
> vector4double a member need to have at least 32-byte alignment on
> the stack. LLVM had been getting this right for most things, but not
> when passing the structure *by value* to a callee (which requires a
> separate copy be made for use by the callee).
> 
> Also, I'd like to make the following point (for everyone): Because of
> the way that the PowerPC ABI is defined, passing an aggregate, no
> matter how small or simple internally, is never exactly the same as
> passing raw data types. At best, it costs you some extra stack
> space. But...
> 
> struct wrapper {
> vector4double x;
> };
> 
> foo(struct wrapper x) { ... }
> bar(vector4double y) { ... }
> 
> When you call bar(y) then y should be passed directly in one of the
> QPX vector registers. When you call foo(x), then x is passed in a
> collection of 64-bit general-purpose registers (as are all
> aggregates), and/or on the stack (depending on how many other
> function parameters there are and in what order they appear). In
> C++, it is almost always better to pass by const reference (unless
> you really do need a copy to modify):
> 
> foo(const wrapper &x) { ... }
> 
> which should be just as easy for the compiler to inline, but is much
> more efficient if you end up with non-inlined calls.
> 
> -Hal
> 
> P.S. For those with your own installs, there is a r185769-20130706-v3
> archive on http://trac.alcf.anl.gov/projects/llvm-bgq which includes
> this fix.
> 
> ----- Original Message -----
> > On 2013-07-11, at 15:50 , Hal Finkel < hfinkel at anl.gov > wrote:
> > 
> > > ----- Original Message -----
> > >> Hal
> > >> 
> > >> Is this content of this archive installed on Vesta? If not, how
> > >> do
> > >> I
> > >> use the content of this archive?
> > > 
> > > Yes, it is installed on vesta (and mira). The archive is just for
> > > other people who have installs on their own.
> > 
> > 
> > Here is my next issue:
> > 
> > The directory is ~eschnett/src/vecmathlib-qpx4, the source file is
> > test.cc. I build with
> > 
> > /home/projects/llvm/bin/bgclang++
> > -I/soft/compilers/ibmcmp-may2013/xlmass/bg/7.3/include -o test
> > test.cc -L/soft/compilers/ibmcmp-may2013/xlmass/bg/7.3/bglib64
> > -lmass_simd
> > 
> 
> [snip]
> 
> > 
> > Current output is in the file 107701.output. This indicates that my
> > function any(boolvec)->bool encounters an error. It is here applied
> > to a boolean vector with all elements set to false, yet the
> > function
> > 
> > bool any() const
> > {
> > return (*this)[0] || (*this)[1] || (*this)[2] || (*this)[3];
> > }
> > 
> > returns true.
> > 
> > -erik
> > 
> > --
> > Erik Schnetter < schnetter at cct.lsu.edu >
> > http://www.perimeterinstitute.ca/personal/eschnetter/
> > 
> > My email is as private as my paper mail. I therefore support
> > encrypting
> > and signing email messages. Get my PGP key from
> > http://keys.gnupg.net .
> > 
> > 
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
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> 
> 

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