Sirraide 6e58e99a07 [Clang] [Sema] Reject non-power-of-2 _BitInt matrix element types (#117487) ...

Essentially, this makes this ill-formed:
```c++
using mat4 = _BitInt(12) [[clang::matrix_type(3, 3)]];
```

This matches preexisting behaviour for vector types (e.g.
`ext_vector_type`), and given that LLVM IR intrinsics for matrices also
take vector types, it seems like a sensible thing to do.

This is currently especially problematic since we sometimes lower matrix
types to LLVM array types instead, and while e.g. `[4 x i32]` and `<4 x
i32>` *probably* have the same similar memory layout (though I don’t
think it’s sound to rely on that either, see #117486), `[4 x i12]` and
`<4 x i12>` definitely don’t.

2024-12-17 02:07:29 +01:00

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