Add fast isodd for BigInt (#35873)

Author: Liozou

base/gmp.jl

@@ -10,7 +10,7 @@ import .Base: *, +, -, /, <, <<, >>, >>>, <=, ==, >, >=, ^, (~), (&), (|), xor,
              sum, trailing_zeros, trailing_ones, count_ones, tryparse_internal,
              bin, oct, dec, hex, isequal, invmod, _prevpow2, _nextpow2, ndigits0zpb,
              widen, signed, unsafe_trunc, trunc, iszero, isone, big, flipsign, signbit,
-             sign, hastypemax
+             sign, hastypemax, isodd
 
 if Clong == Int32
     const ClongMax = Union{Int8, Int16, Int32}
@@ -342,6 +342,8 @@ end
 
 rem(x::Integer, ::Type{BigInt}) = BigInt(x)
 
+isodd(x::BigInt) = MPZ.tstbit(x, 0)
+
 function (::Type{T})(x::BigInt) where T<:Base.BitUnsigned
     if sizeof(T) < sizeof(Limb)
         convert(T, convert(Limb,x))

test/gmp.jl

@@ -412,6 +412,9 @@ end
 # Issue #24298
 @test mod(BigInt(6), UInt(5)) == mod(6, 5)
 
+@test iseven(zero(BigInt))
+@test isodd(BigInt(typemax(UInt)))
+
 @testset "cmp has values in [-1, 0, 1], issue #28780" begin
     # _rand produces values whose log2 is better distributed than rand
     _rand(::Type{BigInt}, n=1000) = let x = big(2)^rand(1:rand(1:n))