hzfan edited a comment on pull request #6771:
URL: https://github.com/apache/incubator-tvm/pull/6771#issuecomment-717639785
@tqchen The ir (before narrowing) is like
```
for (ax0.ax1.fused.ax2.outer.fused: int64, 0i64, 42i64) "parallel" {
for (n.oc_chunk.fused.oh.outer.fused: int64, 0i64,
a_very_long_upper_bound) {
...
...
for (oh.inner: int32, 0, 2) {
for (ow.inner: int32, 0, 14) {
for (oc_block: int32, 0, 16) "vectorized" {
...floormod(n.oc_chunk.fused.oh.outer.fused, cast(int64,
floordiv(((cast(int32, ((floormod(ax0.ax1.fused.ax2.outer.fused, 7i64)*2i64) +
1i64)) + 1) - cast(int32, (floormod(ax0.ax1.fused.ax2.outer.fused,
7i64)*2i64))), 2)))...
}
}
}
}
}
```
Let `a = n.oc_chunk.fused.oh.outer.fused` (the first operand of floormod),
`b = cast(int64, floordiv(((cast(int32,
((floormod(ax0.ax1.fused.ax2.outer.fused, 7i64)*2i64) + 1i64)) + 1) -
cast(int32, (floormod(ax0.ax1.fused.ax2.outer.fused, 7i64)*2i64))), 2))`
(second operand of floormod)
`const_int_bound` gives `0 <= a <= 6` and `-5 <= b <= 7`.
In a simplified form,
```
b = floordiv( cast(i32, c * 2 + 1) + 1 - cast(i32, c * 2), 2)
c = floormod(ax0.ax1.fused.ax2.outer.fused, 7)
```
I guess `cast(i32, c * 2 + 1) + 1 - cast(i32, c * 2)` is not simplified as
`2`, instead, its bound is analyzed directly, so the min becomes negative due
to the minus operation.
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