[mlir][Vector] Relax condition for `splitFullAndPartialTransferPrecondition`

[nicolasvasilache]

Summary

The splitFullAndPartialTransferPrecondition has a restrictive condition to
prevent the pattern to be applied recursively if it is nested under an scf.IfOp.
Relaxing the condition to the immediate parent op must not be an scf.IfOp lets
the pattern be applied more generally while still preventing recursion.

mlir/lib/Dialect/Vector/VectorTransforms.cpp

LogicalResult mlir::vector::splitFullAndPartialTransferPrecondition(
   if (!xferOp.permutation_map().isMinorIdentity())
     return failure();
   // TODO: relax this precondition. This will require rank-reducing subviews.
   if (xferOp.getMemRefType().getRank() != xferOp.getTransferRank())
     return failure();
   // Must have some masked dimension to be a candidate for splitting.
   if (!xferOp.hasMaskedDim())
     return failure();
-  // Don't split transfer operations under IfOp, this avoids applying the
-  // pattern recursively.
-  // TODO: improve the condition to make it more applicable.
-  if (xferOp.getParentOfType<scf::IfOp>())
+  // Don't split transfer operations directly under IfOp, this avoids applying
+  // the pattern recursively.
+  // TODO: improve the filtering condition to make it more applicable.
+  if (isa<scf::IfOp>(xferOp.getOperation()->getParentOp()))
     return failure();
   return success();
 }
 
 /// Given two MemRefTypes `aT` and `bT`, return a MemRefType to which both can
 /// be cast. If the MemRefTypes don't have the same rank or are not strided,
 /// return null; otherwise:
 ///   1. if `aT` and `bT` are cast-compatible, return `aT`.