llvm and openmp

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1

Hi all,

I am new to llvm. Does llvm has support for openmp directives like #pragma openmp threadprivate(var)? If so does the variable ‘var’ can be class objects instead of Plain Old Datatypes (POD) like int, float etc. g++ allows the #pragma openmp threadprivate(var) primitive only for the POD type. Please check the bug link at http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27557 . Please let me know.

Thanks,
karthik

2

Hi Karthik,

I am new to llvm. Does llvm has support for openmp directives like #pragma
openmp threadprivate(var)?

LLVM has no special support for openmp. The LLVM front-ends that support
openmp, namely llvm-gcc and dragonegg, lower openmp constructs down to
library calls the same way GCC does. This is no coincidence: both of those
front-ends are based on GCC and just let the GCC machinery take care of openmp.
The clang front-end does not support openmp.

  If so does the variable 'var' can be class objects

instead of Plain Old Datatypes (POD) like int, float etc. g++ allows the #pragma
openmp threadprivate(var) primitive only for the POD type. Please check the bug
link at 27557 – OpenMP threadprivate directive does not work with non-POD types . Please let me know.

You are out of luck: if GCC rejects this then so will llvm-gcc and dragonegg.
That said, the GCC Ada front-end does support thread-local storage non-POD
types, so it can be done - but it jumps through a lot of hoops and the result
is not very efficient. There's a big comment in gcc/ada/a-tasatt.adb explaining
how it is done and why that scheme was chosen. You may enjoy these lines from
the start of the comment:

   The following notes are provided in case someone decides the implementation
   of this package is too complicated, or too slow. Please read this before
   making any "simplifications".

Ciao, Duncan.

3

Hi Duncan,

Thanks for your prompt reply. Good to know that GCC ADA front end supports this. Since I need to compile a huge c++ project, I am in need of a c++ compiler supporting thread local storage for non POD types. Intel’s c++ compiler does but its non commercial license does not suit my research work. If you know any other c++ compiler kindly let me know.

Note: apologies as I replied to your personal id instead of group

Thanks for your time,
karthik