[SYCL][Clang] Fix address space for virtual table support

[elizabethandrews]

For SPIR, virtual table elements should be emitted in the default address space while global variables should be emitted in address space 1.

Also, only emit virtual functions marked with [[intel::device_indirectly_callable]]. This attribute will be replaced by compile time properties (for this check) once the spec for virtual function extension is finalized.

Patch by: Michael Rice ([email protected]) and Elizabeth Andrews

[elizabethandrews]

FYI - This is upstreaming downstream code (in a simpler way) and tests. Downstream will need to be refactored after this change to remove a bunch of isSPIR checks and use RuntimeGlobalsInt8PtrTy instead.

[elizabethandrews]

Hmm looks like we have some failing lit tests. Not sure why they didn't fail locally. Taking a look now.

[elizabethandrews]

@intel/llvm-gatekeepers this is ready for merge.

[ldrumm]

I'm confused about the authorship here. Is this a case where one of these commits is by you, Elizabeth, and one is Michael?

[elizabethandrews]

No it isn't. We both accidently worked on the same issue and both fixed it. However my version of the patch had unnecessary code and I worked with Mike to keep the relevant portion and added tests (which actually is copies of tests which exist downstream written by Alexey Sachkov).

The code both Mike and I worked on is based on downstream code written by Jennifer Yu. This is a refactored version of downstream code. Once this is checked in, I will cherry-pick it and replace downstream code as well.

[elizabethandrews]

ping @intel/llvm-gatekeepers do you need more clarification on authors? I think you can set either Mike or I as the author here.

[sarnex]

I added Co-authored-by to the commit message for Mike, that should capture everything.

[ldrumm]

Thanks for the clarification. That makes sense. I wanted to avoid an issue we've been having with misattributed cherry-picks.