[RFC][gomp4] Offloading patches (3/3): Add invocation of target compiler

Michael Zolotukhin michael.v.zolotukhin@gmail.com
Thu Jan 16 11:37:00 GMT 2014


On 20 December 2013 20:46, Michael V. Zolotukhin
<michael.v.zolotukhin@gmail.com> wrote:
>> This patch seems to make rather too many assumptions about host and
>> target compilers. Certainly code like this can't go into
>> target-independent code like lto-wrapper.
> That's true.  The point of this patch was to show what is needed to support
> x86->MIC OpenMP offloading, as we currently see it.  We are ready to extend
> existing code making it more versatile, but keeping this needed functionality.
>> Also, I'm not sure you can
>> assume you'll get ELF files out of the OpenACC target compiler; I'd very
>> prefer a solution that doesn't rely on objcopy.
> Yep, that's an issue I suspected but wasn't sure of.
> The idea was to prepare an image in the following steps:
>   1. Compile with target compiler.
>   2. Post-process it (in our case, call objcopy and perform partial linking).
>   3. Pass it to the host linker as a usual object file with the image and its
> size placed in the known symbols with defined names (e.g.
> _omp_<target-name>_image).
> I would like to keep step 3 unchanged, while the steps 1 and 2 could be easily
> combined into a single one.
> In that case we could say that output of a target compiler should be an object
> file for host linker with several symbols defined: _omp_<target-name>_image,
> _omp_<target-name>_size, etc.
> For x86->MIC one would use gcc+objcopy for this, and for OpenACC offloading one
> could use gcc+some of other target-specific utils (if any of them needed).
> Will this scheme work for OpenACC?
> Michael
>> Bernd

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