8b67f36258
This fixes the current lowering of `arith.ceildivsi` in the arith-expand pass, which was previously incorrect. The new version is based on the lowering of `arith.floordivsi`, and will not introduce new undefined behavior or poison during the lowering. It also replaces one division with a multiplication. The previous lowering of `ceildivsi(n, m)` was the following: ``` x = (m > 0) ? -1 : 1 (n*m>0) ? ((n+x) / m) + 1 : - (-n / m) ``` This caused two problems: * In the case where `n` is INT_MIN and `m` is positive, the result would be poison instead of an actual value * In the case where `n` is INT_MAX and `m` is `-1`, this would trigger undefined behavior, while the original code wouldn't. This is because `n+x` would be equal to `INT_MIN` (`INT_MAX + 1`), so the `(n+x) / m` division would overflow and trigger UB.
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