0c9a02355a
@jeanPerier explained the importance of converting box loads and stores into `memcpy`s instead of aggregate loads and stores, and I'll do my best to explain it here. * [(godbolt link) Example comparing opt transformations on memcpys vs aggregate load/stores](https://godbolt.org/z/be7xM83cG) * LLVM can more effectively reason about memcpys compared to aggregate load/stores. * This came up when others were discussing array descriptors for assumed-rank arrays passed to `bind(c)` subroutines, with the implication that the array descriptors are known to have lower bounds of 1 and that they are not pointer/allocatable types. * [(godbolt link) Clang also uses memcpys so we should probably follow them, assuming the clang developers are generatign what they know Opt will handle more effectively.](https://godbolt.org/z/YT4x7387W) * This currently may not help much without the `nocapture` attribute being propagated to function calls, but [it looks like someone may do this soon (discourse link)](https://discourse.llvm.org/t/applying-the-nocapture-attribute-to-reference-passed-arguments-in-fortran-subroutines/81401/23) or I can do this in a follow-up patch. Note on test `flang/test/Fir/embox-char.fir`: it looks like the original test was auto-generated. I wasn't too sure which parts were especially important to test, so I regenerated the test. If we want the updated version to look more like the old version, I'll make those changes.
Flang Integration Tests
This directory can be used to add Integration tests involving multiple stages of the compiler (for eg. from Fortran to LLVM IR). It should not contain executable tests. We should only add tests here sparingly and only if there is no other way to test. Repeat this message in each test that is added to this directory and sub-directories.