On Sat, 2025-07-19 at 16:22 +0200, Paul Chaignon wrote:
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
[...]
> + /* If the s64 range crosses the sign boundary, then it's split
> + * between the beginning and end of the U64 domain. In that
> + * case, we can derive new bounds if the u64 range overlaps
> + * with only one end of the s64 range.
> + *
> + * In the following example, the u64 range overlaps only with
> + * positive portion of the s64 range.
> + *
> + * 0 U64_MAX
> + * | [xxxxxxxxxxxxxx u64 range xxxxxxxxxxxxxx] |
> + * |----------------------------|----------------------------|
> + * |xxxxx s64 range xxxxxxxxx] [xxxxxxx|
> + * 0 S64_MAX S64_MIN -1
> + *
> + * We can thus derive the following new s64 and u64 ranges.
> + *
> + * 0 U64_MAX
> + * | [xxxxxx u64 range xxxxx] |
> + * |----------------------------|----------------------------|
> + * | [xxxxxx s64 range xxxxx] |
> + * 0 S64_MAX S64_MIN -1
> + *
> + * If they overlap in two places, we can't derive anything
> + * because reg_state can't represent two ranges per numeric
> + * domain.
> + *
> + * 0 U64_MAX
> + * | [xxxxxxxxxxxxxxxxx u64 range xxxxxxxxxxxxxxxxx] |
> + * |----------------------------|----------------------------|
> + * |xxxxx s64 range xxxxxxxxx] [xxxxxxxxxx|
> + * 0 S64_MAX S64_MIN -1
> + *
> + * The first condition below corresponds to the diagram above.
> + * The second condition considers the case where the u64 range
> + * overlaps with the negative porition of the s64 range.
> + */
> + if (reg->umax_value < (u64)reg->smin_value) {
> + reg->smin_value = (s64)reg->umin_value;
> + reg->umax_value = min_t(u64, reg->umax_value, reg->smax_value);
> + } else if ((u64)reg->smax_value < reg->umin_value) {
Nit: I'd add a drawing here as well:
* 0 U64_MAX
* | [xxxxxxxxxxxxxx u64 range xxxxxxxxxxxxxx] |
* |----------------------------|----------------------------|
* |xxxxxxxxx] [xxxxxxxxxxxx s64 range |
* 0 S64_MAX S64_MIN -1
> + reg->smax_value = (s64)reg->umax_value;
> + reg->umin_value = max_t(u64, reg->umin_value, reg->smin_value);
> + }
> }
> }
>
