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Re: [PATCH][RFC][OpenMP] Forbid target* pragmas in target regions

On Mon, Jan 12, 2015 at 12:22:44AM +0300, Ilya Verbin wrote:
> Currently if a target* pragma appears within a target region, GCC successfully
> compiles such code (with a warning).  But the binary fails at run-time, since it
> tries to call GOMP_target* functions on target.
> The spec says: "If a target, target update, or target data construct appears
> within a target region then the behavior is unspecified."
> I see 2 options to make the behavior more user-friendly:
> 1. To return an error at compile-time.
> 2. To check at run-time in libgomp whether GOMP_target* is called on target, and
> perform target-fallback if so.
> If we will select option #1, the patch is ready.

Option #1 is just wrong.  There is nothing wrong with such constructs
appearing in #pragma omp declare target functions etc., the problem is
if you hit them at runtime.  You can very well have say #pragma omp declare
target function, that optionally invokes #pragma omp target region e.g.
based on its parameters, state of global variables, what other functions
return etc. - and the program can be written so that that condition just
never happens if the function is already offloaded.


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