What is done in this PR:
- [x] Add `ConvertLayout`, `getSizePerThread` and `getShapePerCTA`
implementation for `SliceEncodingAttr`
- [x] Split `emitIndices` into two phases:
`emitBaseIndexForBlockedLayout` and `emitOffsetForBlockedLayout`
- [x] Add `ReduceOpConversion::matchAndRewriteBasic` implementation
- [x] Add `ReduceOpConversion::matchAndRewriteFast` implementation with
ptx instruction `shfl.sync`
- [x] Add support for scalar value in `StoreOpConversion`
- [x] Add Reduce1d and Reduce2d unit tests and pass all unit tests
Co-authored-by: Qingyi Liu <liuqingyi1993@gmail.com>
