proper handling for barrier call attributes

The recent PR #1407 fixed barrier call attributes, but only for the conversion from SPIR-V to the OpenCL C 2.0-style LLVM IR. Is the same change also needed for the conversion to the OpenCL C 1.2-style LLVM IR?

Is there a way to write a test to observe the behavior when the barrier call attributes are not handled properly?

I'm also asking this question because it's unclear if I need to add a similar fix for my recent split barrier extension:

* https://github.com/KhronosGroup/SPIRV-LLVM-Translator/pull/1424

Thanks!

Start by reviewing PR #1407 and comparing the SPIR-V-to-OpenCL C 2.0-style and 1.2-style LLVM IR conversion paths. Investigate whether barrier call attributes differ between them, and determine whether a test can expose the incorrect behavior; also consider the related split barrier extension in PR #1424.

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