Forward aliasing check for ReshapedArrays to the parent (#54168)

Author: jishnub

base/reshapedarray.jl

@@ -225,6 +225,11 @@ elsize(::Type{<:ReshapedArray{<:Any,<:Any,P}}) where {P} = elsize(P)
 
 unaliascopy(A::ReshapedArray) = typeof(A)(unaliascopy(A.parent), A.dims, A.mi)
 dataids(A::ReshapedArray) = dataids(A.parent)
+# forward the aliasing check the parent in case there are specializations
+mightalias(A::ReshapedArray, B::ReshapedArray) = mightalias(parent(A), parent(B))
+# special handling for reshaped SubArrays that dispatches to the subarray aliasing check
+mightalias(A::ReshapedArray, B::SubArray) = mightalias(parent(A), B)
+mightalias(A::SubArray, B::ReshapedArray) = mightalias(A, parent(B))
 
 @inline ind2sub_rs(ax, ::Tuple{}, i::Int) = (i,)
 @inline ind2sub_rs(ax, strds, i) = _ind2sub_rs(ax, strds, i - 1)

test/subarray.jl

@@ -1120,3 +1120,19 @@ end
         end
     end
 end
+
+@testset "aliasing check with reshaped subarrays" begin
+    C = rand(2,1)
+    V1 = @view C[1, :]
+    V2 = @view C[2, :]
+
+    @test !Base.mightalias(V1, V2)
+    @test !Base.mightalias(V1, permutedims(V2))
+    @test !Base.mightalias(permutedims(V1), V2)
+    @test !Base.mightalias(permutedims(V1), permutedims(V2))
+
+    @test Base.mightalias(V1, V1)
+    @test Base.mightalias(V1, permutedims(V1))
+    @test Base.mightalias(permutedims(V1), V1)
+    @test Base.mightalias(permutedims(V1), permutedims(V1))
+end