This patch restricts the triangular loop iteration count optimization to
only apply to nested triangular loops (`depth >= 2`), not first-level
triangular loops.
The optimization computes iterations as `(Upper - Lower + 1`) for
triangular loops where the inner loop bound depends on an outer loop
counter. However, this formula only works correctly for deeply nested
triangular dependencies: `k` depends on `j`, and `j` itself depends on
`i` For first-level triangular loops: `k` depends directly on `i`, the
standard iteration count formula handles the calculation correctly.
