The "small range with constant divisor" optimization in
`inferAffineExpr` for `AffineExprKind::Mod` assumed that if the dividend
range span (`lhsMax - lhsMin`) is less than the divisor, then the mod
results form a contiguous range. This is not always true, as the range
can straddle a modulus boundary.
For example, `[14, 17] mod 8`:
- Span is 3 < 8, so the old condition passed
- But `14%8=6` and `17%8=1` (wraps at 16)
- `umin=6, umax=1` → assertion `umin.ule(umax)` fails
The fix adds a same-quotient check (`lhsMin/rhs == lhsMax/rhs`) to
ensure both endpoints fall within the same modular period. When they
don't, we fall back to the conservative `[0, divisor-1]` range.
Assisted-by: Cursor (Claude)
Signed-off-by: Yu-Zhewen <zhewenyu@amd.com>
a7bf24919f