[BUILD] Enable optional standalone spirv-tools

[doctaweeks]

libspirv.h is packaged with spirv-tools: spirv-tools/libspirv.h

[tqchen]

hmm, does this change happens in the recent VulkanSDK? Normally files will be copied if you do build tools after you install vulkan sdk

[doctaweeks]

This is with spirv-tools 2018.2

[tqchen]

The default build assumes the installation of vulkan sdk https://vulkan.lunarg.com/sdk/home, which comes with spirv-tools, and if you run ./build_tools.sh under the sdk root, you should be able to get spirv-tools in the corresponding folder. If you use a standalone spirv-tools, maybe we need to update the CMake search rule to do so

[doctaweeks]

I have a standalone spirv-tools. I think updating the search rule would be useful for any distro that packages the vulkan components separately.

[tqchen]

sounds reasonable, are you interested in sending a patch?

[tqchen]

This likely will involve modification of the following two files

• https://github.com/dmlc/tvm/blob/master/cmake/modules/Vulkan.cmake
• https://github.com/dmlc/tvm/blob/master/cmake/util/FindVulkan.cmake

We can introduce an optional option USE_SPRIV and use that info when this is set

[doctaweeks]

Rather than an option I think it's fine to check for one, then the other, and just use the one that's found. I suspect it's unlikely for someone to have it installed both ways.

[tqchen]

that also works

[tqchen]

@doctaweeks any updates on this? would you like to send a patch?

[doctaweeks]

I haven't had a chance to revisit this in depth yet.

I can add that a complete fix for this will be a little more complicated. There is a separate pkgconfig file for spirv-tools that should probably be used (currently "find_package(Vulkan").

I'll try to get to it this week.

[tqchen]

close by #1298