Disallows initialization of scalable vectors with an attribute of
arbitrary values, e.g.:
```mlir
%c = arith.constant dense<[0, 1]> : vector<[2] x i32>
```
Initialization using vector splats remains allowed (i.e. when all the
init values are identical):
```mlir
%c = arith.constant dense<[1, 1]> : vector<[2] x i32>
```
Note: This is a re-upload of #86178
Adds support for scalable vectors to patterns defined in
VectorLineralize.cpp.
Linearization is disable in 2 notable cases:
* vectors with more than 1 scalable dimension (we cannot represent
vscale^2),
* vectors initialised with arith.constant that's not a vector splat
(such arith.constant Ops cannot be flattened).
This patch refactors the `linearize.mlir` test - currently it contains
some duplication and can be tricky to follow.
Summary of changes:
* reduce duplication by introducing a shared check prefix (`ALL`) and
by introducing `-check-prefixes`,
* make sure that every "check" line is directly above the
corresponding line of input MLIR,
* group check lines corresponding to a particular prefix together (so
that it's easier to see the expected output for a particular
prefix),
* remove `CHECK` from prefix names (with multiple prefixes that's just
noise that can be avoided) and use a bit more descriptive prefixes
instead (`CHECK0` -> `BW-0`, where `BW` stands for bitwidth),
* unify indentation,
* `nonvec_result` -> `test_tensor_no_linearize` (for consistency with
`test_index_no_linearize`).
NOTE: This change only updates the format of the "CHECK" lines and
doesn't affect what's being tested.
This change is intended as preparation for adding support for scalable
vectors to `LinearizeConstant` and `LinearizeVectorizable` - i.e.
patterns that `linearlize.mlir` is meant to test.
Common backends (LLVM, SPIR-V) only supports 1D vectors, LLVM conversion
handles ND vectors (N >= 2) as `array<array<... vector>>` and SPIR-V
conversion doesn't handle them at all at the moment. Sometimes it's
preferable to treat multidim vectors as linearized 1D. Add pass to do
this. Only constants and simple elementwise ops are supported for now.
@krzysz00 I've extracted yours result type conversion code from
LegalizeToF32 and moved it to common place.
Also, add ConversionPattern class operating on traits.
