[mlir][SCF] Use symbols in loop peeling rewrite

[springerm]

Summary

Use symbols in the affine map instead of dims. Dims should not be divided.

[ftynse]

I think dims can be dividends but not divisors.

mlir/lib/Dialect/SCF/Transforms/LoopSpecialization.cpp

static LogicalResult peelForLoop(RewriterBase &b, ForOp forOp, scf::IfOp &ifOp,
   // No specialization necessary if step already divides upper bound evenly.
   if (lbInt && ubInt && stepInt && (*ubInt - *lbInt) % *stepInt == 0)
     return failure();
   // No specialization necessary if step size is 1.
   if (stepInt == static_cast<int64_t>(1))
     return failure();
 
   auto loc = forOp.getLoc();
-  AffineExpr dim0, dim1, dim2;
-  bindDims(b.getContext(), dim0, dim1, dim2);
+  AffineExpr sym0, sym1, sym2;
+  bindSymbols(b.getContext(), sym0, sym1, sym2);
   // New upper bound: %ub - (%ub - %lb) mod %step
-  auto modMap = AffineMap::get(3, 0, {dim1 - ((dim1 - dim0) % dim2)});
+  auto modMap = AffineMap::get(0, 3, {sym1 - ((sym1 - sym0) % sym2)});
   b.setInsertionPoint(forOp);
   splitBound = b.createOrFold<AffineApplyOp>(
       loc, modMap,
       ValueRange{forOp.lowerBound(), forOp.upperBound(), forOp.step()});
 
   // Set new upper loop bound.
   Value previousUb = forOp.upperBound();
   b.updateRootInPlace(forOp,