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optimize length(::OrdinalRange) for large bit-ints #58864

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Merged
merged 5 commits into from
Jul 16, 2025
Merged

optimize length(::OrdinalRange) for large bit-ints #58864

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768e32e
optimize `length(::OrdinalRange)` for large bit-ints
mbauman Jul 1, 2025
e3e0389
remove max
mbauman Jul 1, 2025
62c3a44
make robust to non-bits steps
mbauman Jul 2, 2025
977cd9d
Merge remote-tracking branch 'origin/master' into mb+n5/ordinal-length
mbauman Jul 2, 2025
d0e1595
remove unneeded at-inline
mbauman Jul 2, 2025
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15 changes: 4 additions & 11 deletions base/range.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -805,17 +805,10 @@ let bigints = Union{Int, UInt, Int64, UInt64, Int128, UInt128},
s = step(r)
diff = last(r) - first(r)
isempty(r) && return zero(diff)
# if |s| > 1, diff might have overflowed, but unsigned(diff)÷s should
# therefore still be valid (if the result is representable at all)
# n.b. !(s isa T)
if s isa Unsigned || -1 <= s <= 1 || s == -s
a = div(diff, s) % typeof(diff)
elseif s < 0
a = div(unsigned(-diff), -s) % typeof(diff)
else
a = div(unsigned(diff), s) % typeof(diff)
end
return a + oneunit(a)
# compute `(diff ÷ s) + 1` in a manner robust to overflow
# by using the absolute values as unsigneds for non-empty ranges
a = div(unsigned(flipsign(diff, s)), unsigned(abs(s))) % typeof(diff)
return max(a + oneunit(a), zero(a))
end
function checked_length(r::OrdinalRange{T}) where T<:bigints
s = step(r)
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