Add C Interface for Optimizer

[daniel-story]

This PR implements a C interface for the Optimizer class. It follows the same pattern established by the existing C interfaces for other classes in SPIRV-Tools.

[dneto0]

This looks good.
But it needs at least one test to cover the new functionality.

Please add a test/opt/c_interface_test.cpp

[dneto0]

And remember to update both
CMakeLists.txt
Android.mk

[s-perron]

I agree. Looks good. It just needs a test. Than the CI will let you know if you missed any build files.

[s-perron]

@daniel-story Are you still working on this?

[daniel-story]

Apologies for the lack of movement on this.

Yes, I am still intending to work on this, but more time sensitive work has been taking precedence. It was less time-consuming to propose the PR in its current form as the C interface code was already written and being used in our fork, but I'll need to find time to implement the test code.

As an aside, looking over this again I think it may also make sense to make two small tweaks to the spvOptimizerRun() parameters:

• Change optimized_binary to a pointer to a spv_binary (obviously itself a pointer to a spv_binary_t) so that the function can return an internally newed spv_binary which can be freed by the caller using spvBinaryDestroy() like the other spv_binary-returning functions (for example spvTextToBinary())
• Potentially change original_binary to an unsigned int* and size_t make it more straightforward for callers to use with SPIR-V that came from outside the SPIRV-Tools ecosystem (for example from glslang), and to match spvBinaryToText()

I feel pretty strongly in favor of the first change, and more in favor than not about the second. Do you have any thoughts?

Assuming you're on board with these, I'll try to make both changes and push them along with the tests sometime within the next 2 weeks.

[s-perron]

Change optimized_binary to a pointer to a spv_binary (obviously itself a pointer to a spv_binary_t) so that the function can return an internally newed spv_binary which can be freed by the caller using spvBinaryDestroy() like the other spv_binary-returning functions (for example spvTextToBinary())

For consistency, I think that is a good idea.

Potentially change original_binary to an unsigned int* and size_t make it more straightforward for callers to use with SPIR-V that came from outside the SPIRV-Tools ecosystem (for example from glslang), and to match spvBinaryToText()

Sure.

[daniel-story]

I’ve added a set of tests for the newly added functionality. I also updated the CMakeLists.txt and verified that a full test run passes successfully.

Regarding the Android tests, I couldn’t find anywhere to add these tests to the Android.mk miles as none of the Android.mk files in the project include seem to include any of the tests currently. I don’t think it’s realistic to expect this PR to port all the tests in SPIRV-Tools to Android, not just because it seems very out of scope but also because I’m not set up to build or run anything on Android.

Please let me know if you have any more comments, or if I missed or misunderstood something. Otherwise, this PR should be ready to merge.

[s-perron]

The windows 2019 bots probably failed because you need to rebase. I'll merge anyway. Other windows tests passed.