Add CUSTOMIZABLE_PIVOT compat

Author: YingboMa

src/lu.jl

@@ -22,22 +22,30 @@ function lu(A::AbstractMatrix, pivot = Val(true), thread = Val(true); kwargs...)
     return lu!(copy(A), normalize_pivot(pivot), thread; kwargs...)
 end
 
+const CUSTOMIZABLE_PIVOT = VERSION >= v"1.8.0-DEV.1507"
+
 struct NotIPIV <: AbstractVector{BlasInt}
     len::Int
 end
 Base.size(A::NotIPIV) = (A.len,)
 Base.getindex(::NotIPIV, i::Int) = i
 Base.view(::NotIPIV, r::AbstractUnitRange) = NotIPIV(length(r))
-init_pivot(::Val{false}, minmn) = NotIPIV(minmn)
+function init_pivot(::Val{false}, minmn)
+    @static if CUSTOMIZABLE_PIVOT
+        NotIPIV(minmn)
+    else
+        init_pivot(Val(true), minmn)
+    end
+end
 init_pivot(::Val{true}, minmn) = Vector{BlasInt}(undef, minmn)
 
-if isdefined(LinearAlgebra, :_ipiv_cols!)
+if CUSTOMIZABLE_PIVOT && isdefined(LinearAlgebra, :_ipiv_cols!)
     function LinearAlgebra._ipiv_cols!(::LU{<:Any, <:Any, NotIPIV}, ::OrdinalRange,
                                        B::StridedVecOrMat)
         return B
     end
 end
-if isdefined(LinearAlgebra, :_ipiv_rows!)
+if CUSTOMIZABLE_PIVOT && isdefined(LinearAlgebra, :_ipiv_rows!)
     function LinearAlgebra._ipiv_rows!(::LU{<:Any, <:Any, NotIPIV}, ::OrdinalRange,
                                        B::StridedVecOrMat)
         return B
@@ -47,12 +55,13 @@ end
 function lu!(A, pivot = Val(true), thread = Val(true); check = true, kwargs...)
     m, n = size(A)
     minmn = min(m, n)
+    npivot = normalize_pivot(pivot)
     # we want the type on both branches to match. When pivot = Val(false), we construct
-    # a `NotIPIV`, which `LinearAlgebra.generic_lufact!` does not. 
+    # a `NotIPIV`, which `LinearAlgebra.generic_lufact!` does not.
     F = if pivot === Val(true) && minmn < 10 # avx introduces small performance degradation
         LinearAlgebra.generic_lufact!(A, to_stdlib_pivot(pivot); check = check)
     else
-        lu!(A, init_pivot(pivot, minmn), normalize_pivot(pivot), thread; check = check,
+        lu!(A, init_pivot(npivot, minmn), npivot, thread; check = check,
             kwargs...)
     end
     return F
@@ -80,6 +89,9 @@ function lu!(A::AbstractMatrix{T}, ipiv::AbstractVector{<:Integer},
     info = zero(BlasInt)
     m, n = size(A)
     mnmin = min(m, n)
+    if pivot === Val(false) && !CUSTOMIZABLE_PIVOT
+        copyto!(ipiv, 1:mnmin)
+    end
     if recurse(A) && mnmin > threshold
         if T <: Union{Float32, Float64}
             GC.@preserve ipiv A begin info = recurse!(view(PtrArray(A), axes(A)...), pivot,
@@ -116,7 +128,7 @@ end
         # [AL AR]
         AL = @view A[:, 1:m]
         AR = @view A[:, (m + 1):n]
-        apply_permutation!(ipiv, AR, Val{Thread}())
+        Pivot && apply_permutation!(ipiv, AR, Val{Thread}())
         ldiv!(_unit_lower_triangular(AL), AR, Val{Thread}())
     end
     info