Support non-caching behavior in call_cached_indirect_function.

[mcourteaux]

This allows one to dynamically change CPU target features which are allowed and which are not allowed to run performance benchmarks. Also can be used to latency-hide GPU Compute API setup by returning "not_right_now" when asked for e.g. CUDA.

The LLVM bit was done with the help of Gemini Pro 3.1, but I went through it and understood it all. Validated the logic with Hopper Disassembler:

Breaking changes

While not technically ABI breaking, your compiler might complain if you have created your own halide_can_use_target_features() as the return-type is now halide_can_use_target_features_result_t instead of int.

We could revert it to int if people want that. Personally, I would like to get an error about this, as that reveals to me there is a new feature. Dealing with this change is trivial:

• return 0; becomes return halide_can_use_feature_never;
• return 1; becomes return halide_can_use_feature_always;
• Change the return type, like I stated above.

UPDATE: I reverted the return type of that function to int to not break anyone's existing code.

Checklist

• Tests added or updated (not required for docs, CI config, or typo fixes)
• Documentation updated (if public API changed)
• Python bindings updated (if public API changed)
• Benchmarks are included here if the change is intended to affect performance.
• Commits include AI attribution where applicable (see Code of Conduct)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.03%. Comparing base (03a18bb) to head (56aed72).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9320      +/-   ##
==========================================
+ Coverage   69.83%   70.03%   +0.20%     
==========================================
  Files         258      258              
  Lines       78210    78225      +15     
  Branches    19037    19037              
==========================================
+ Hits        54617    54787     +170     
+ Misses      17832    17791      -41     
+ Partials     5761     5647     -114     

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