[PATCH, 4/16] Implement -foffload-alias

Jakub Jelinek jakub@redhat.com
Wed Nov 11 11:01:00 GMT 2015


On Wed, Nov 11, 2015 at 11:51:02AM +0100, Richard Biener wrote:
> > The option -foffload-alias=pointer instructs the compiler to assume that
> > objects references in an offload region do not alias.
> > 
> > The option -foffload-alias=all instructs the compiler to make no
> > assumptions about aliasing in offload regions.
> > 
> > The default value is -foffload-alias=none.
> 
> I think global options for this is nonsense.  Please follow what
> we do for #pragma GCC ivdep for example, thus allow the alias
> behavior to be specified per "region" (whatever makes sense here
> in the context of offloading).

Yeah, completely agreed.  I don't see why the offloaded region would be in
any way special, they are C/C++/Fortran code as any other.
What we can and should improve is teach IPA aliasing/points to analysis
about the way we lower the host vs. offloading region boundary, so that
if alias analysis on the caller of GOMP_target_ext/GOACC_parallel_keyed
determines something it can be used on the offloaded function side and vice
versa, but a switch like the above is just wrong.

	Jakub



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