[MLIR][Affine] Expose region-based isTopLevelValue

[wsmoses]

Summary

This PR exposes the region-based isTopLevelValue,
which is useful for other code that performs Affine transformations,
but is not within AffineOps.cpp

[bondhugula]

mlir/include/mlir/Dialect/Affine/IR/AffineOps.h

33–41

TODO here: these should be renamed if they are on the mlir namespace -- ideally, they should go on a mlir::affine:: namespace.

mlir/include/mlir/Dialect/Affine/IR/AffineOps.h

 class AffineApplyOp;
 class AffineBound;
 class AffineValueMap;
 
 /// A utility function to check if a value is defined at the top level of an
 /// op with trait `AffineScope` or is a region argument for such an op. A value
 /// of index type defined at the top level is always a valid symbol for all its
 /// uses.
 bool isTopLevelValue(Value value);
 
+/// A utility function to check if a value is defined at the top level of
+/// `region` or is an argument of `region`. A value of index type defined at the
+/// top level of a `AffineScope` region is always a valid symbol for all
+/// uses in that region.
+bool isTopLevelValue(Value value, Region *region);
+
 /// Returns the closest region enclosing `op` that is held by an operation with
 /// trait `AffineScope`; `nullptr` if there is no such region.
 Region *getAffineScope(Operation *op);
 
 /// AffineDmaStartOp starts a non-blocking DMA operation that transfers data
 /// from a source memref to a destination memref. The source and destination
 /// memref need not be of the same dimensionality, but need to have the same
 /// elemental type. The operands include the source and destination memref's
 /// each followed by its indices, size of the data transfer in terms of the

mlir/lib/Dialect/Affine/IR/AffineOps.cpp

 #define DEBUG_TYPE "affine-analysis"
 
 #include "mlir/Dialect/Affine/IR/AffineOpsDialect.cpp.inc"
 
 /// A utility function to check if a value is defined at the top level of
 /// `region` or is an argument of `region`. A value of index type defined at the
 /// top level of a `AffineScope` region is always a valid symbol for all
 /// uses in that region.
-static bool isTopLevelValue(Value value, Region *region) {
+bool mlir::isTopLevelValue(Value value, Region *region) {
   if (auto arg = value.dyn_cast<BlockArgument>())
     return arg.getParentRegion() == region;
   return value.getDefiningOp()->getParentRegion() == region;
 }
 
 /// Checks if `value` known to be a legal affine dimension or symbol in `src`
 /// region remains legal if the operation that uses it is inlined into `dest`
 /// with the given value mapping. `legalityCheck` is either `isValidDim` or