Patterns in `LowerContractionToSMMLAPattern` are designed to handle
vector-to-matrix multiplication but not matrix-to-vector. This leads to
the following error when processing `rhs` with rank < 2:
```
iree-compile: /usr/local/google/home/kooljblack/code/iree-build/llvm-project/tools/mlir/include/mlir/IR/BuiltinTypeInterfaces.h.inc:268: int64_t mlir::detail::ShapedTypeTrait<mlir::VectorType>::getDimSize(unsigned int) const [ConcreteType = mlir::VectorType]: Assertion `idx < getRank() && "invalid index for shaped type"' failed.
```
Updates to explicitly check the rhs rank and fail cases that cannot
process.
Updates smmla unrolling patterns to handle vecmat contracts where `dimM=1`. This includes explicit vecmats in the form: `<1x8xi8> x <8x8xi8> --> <1x8xi32>` or implied with the leading dim folded: `<8xi8> x <8x8xi8> --> <8xi32>`
Since the smmla operates on two `<2x8xi8>` input vectors to produce `<2x2xi8>` accumulators, half of each 2x2 accumulator tile is dummy data not pertinent to the computation, resulting in half throughput.
This patch updates `LowerContractionToSMMLAPattern` to unroll larger vector contracts into multiple smmla instructions.
Now accepts up to [8,8,8] tiles (previously only [2,2,8]). The N/M dimensions must be powers of 2. `vector.extract_strided_slice`/`vector.insert_strided_slice` divides the contract into tiles to be processed in a row.
This patch adds a the `LowerVectorToArmNeonPattern` patterns to the
ArmNeon.
This pattern inspects `vector.contract` ops that can be 1-1 mapped to an
`arm.neon.smmla` intrinsic. The contract ops must be separated into
tiles who's inputs must fit that of a single smmla op (`2x8xi32` inputs
and `2x2xi32` output). The `vector.contract` inputs must be sign
extended from narrow types (<=i8) to be converted. If all conditions are
met, an smmla op is inserted with additional `vector.shape_casts` to
handle linearizing the input and output dimension.
