Add rank-0 memref support to MemRefToEmitC and the EmitC TypeConverter,
needed for lowering the models generated by:
- `llvm/lib/Analysis/models/gen-inline-oz-test-model.py`
- `llvm/lib/Analysis/models/gen-regalloc-eviction-test-model.py`
Rank-0 memrefs are no longer rejected by `isMemRefTypeLegalForEmitC`.
The EmitC type converter maps `memref<T>` to `!emitc.ptr<T>`, giving
rank-0 memrefs addressable scalar storage.
`memref.alloc` now allocates one element for rank-0 memrefs.
`memref.dealloc` frees the pointer-backed value. `memref.load` and
`memref.store` lower rank-0 accesses through `emitc.subscript %ptr[0]`,
followed by `emitc.load` or `emitc.assign`. `memref.copy` lowers rank-0
copies as scalar load plus assign.
`memref.alloca` still rejects rank-0 memrefs because this patch only
supports pointer-backed rank-0 lowering.
The pointer recovery helper now accepts both direct `emitc.ptr<T>`
values and pointer values behind `builtin.unrealized_conversion_cast`,
which is needed by dealloc, copy, load, and store depending on where the
value comes from in conversion.
Tests cover rank-0 alloc/dealloc, load/store, alloc-backed load/store,
and copy. Removed cases this patch adds support for (rank-0) from
`func-to-emitc-failed`.
Assisted-by: Codex (refine implementation + tests). I reviewed all code
and tests before submission.
ioana ghiban
5ae6537bba