Fix for a crash reported in #64975.
The crash occurs in the cast located
[here](ece5dd101c/mlir/lib/Analysis/DataFlow/DeadCodeAnalysis.cpp (L262))
because `llvm.unreachable` doesn't implement
`RegionBranchTerminatorOpInterface`.
The crash is caused by `DeadCodeAnalysis` assuming that
`isa<RegionBranchOpInterface>(op->getParentOp())` implies
`isa<RegionBranchTerminatorOpInterface>(op)` in
`DeadCodeAnalysis::visit()`.
This patch tried to fix this by enabling the analysis to proceed
regardless of whether `op` is a `RegionBranchTerminatorOpInterface`.
The PredecessorState in dead code analysis does not register
zero-operand returns as predecessors of their corresponding call ops.
This causes bugs with dense dataflow analyses that use dead code
analysis to query for the predecessors of CallOpInterfaces.
This was reasonable for sparse analyses, but isn't for dense ones.
This is generated by running
```
sed --in-place 's/[[:space:]]\+$//' mlir/**/*.td
sed --in-place 's/[[:space:]]\+$//' mlir/**/*.mlir
```
Reviewed By: rriddle, dcaballe
Differential Revision: https://reviews.llvm.org/D138866
This patch implements the analysis state classes needed for sparse data-flow analysis and implements a dead-code analysis using those states to determine liveness of blocks, control-flow edges, region predecessors, and function callsites.
Depends on D126751
Reviewed By: rriddle, phisiart
Differential Revision: https://reviews.llvm.org/D127064
