fix saturating float-to-int cast#4573
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The issue is that Kani computes int_max_as_float by casting u64::MAX to f64. But u64::MAX (2^64 - 1) isn't exactly representable in f64, so it rounds *up* to 2^64. The old code used a greater-than operation, which would mean a float value equal to exactly 2^64 fails this check, falls through the raw truncation path, and produces a wrong result instead of saturating to u64::MAX. Instead we use greater-than-or-equal so that the boundary value 2^64 correctly saturates. This is safe for types where the max IS exactly representable.
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The remaining failures don't seem related to this PR? |
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@feliperodri sorry to bother, but any progress? |
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The issue is that Kani computes int_max_as_float by casting u64::MAX to f64. But u64::MAX (2^64 - 1) isn't exactly representable in f64, so it rounds up to 2^64. The old code used a greater-than operation, which would mean a float value equal to exactly 2^64 fails this check, falls through the raw truncation path, and produces a wrong result instead of saturating to u64::MAX.
Instead we use greater-than-or-equal so that the boundary value 2^64 correctly saturates. This is safe for types where the max IS exactly representable.
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