edge case: tril!, triu! and I constructors with empty matrices

src/host/construction.jl

@@ -37,9 +37,10 @@ end
 function (T::Type{<: AnyGPUArray{U}})(s::UniformScaling, dims::Dims{2}) where {U}
     res = similar(T, dims)
     fill!(res, zero(U))
+    isempty(res) && return res
     kernel = identity_kernel(get_backend(res))
     kernel(res, size(res, 1), s.λ; ndrange=minimum(dims))
-    res
+    return res
 end
 
 (T::Type{<: AnyGPUArray})(s::UniformScaling{U}, dims::Dims{2}) where U = T{U}(s, dims)
@@ -48,9 +49,10 @@ end
 
 function Base.copyto!(A::AbstractGPUMatrix{T}, s::UniformScaling) where T
     fill!(A, zero(T))
+    isempty(A) && return A
     kernel = identity_kernel(get_backend(A))
     kernel(A, size(A, 1), s.λ; ndrange=minimum(size(A)))
-    A
+    return A
 end
 
 function _one(unit::T, x::AbstractGPUMatrix) where {T}

src/host/linalg.jl

@@ -165,27 +165,29 @@ for T in (UpperTriangular, LowerTriangular, UnitUpperTriangular, UnitLowerTriang
 end
 
 function LinearAlgebra.tril!(A::AbstractGPUMatrix{T}, d::Integer = 0) where T
-  @kernel function tril_kernel!(_A, _d)
-    I = @index(Global, Cartesian)
-    i, j = Tuple(I)
-    if i < j - _d
-      @inbounds _A[i, j] = zero(T)
+    isempty(A) && return A
+    @kernel function tril_kernel!(_A, _d)
+        I = @index(Global, Cartesian)
+        i, j = Tuple(I)
+        if i < j - _d
+            @inbounds _A[i, j] = zero(T)
+        end
     end
-  end
-  tril_kernel!(get_backend(A))(A, d; ndrange = size(A))
-  return A
+    tril_kernel!(get_backend(A))(A, d; ndrange = size(A))
+    return A
 end
 
 function LinearAlgebra.triu!(A::AbstractGPUMatrix{T}, d::Integer = 0) where T
-  @kernel function triu_kernel!(_A, _d)
-    I = @index(Global, Cartesian)
-    i, j = Tuple(I)
-    if j < i + _d
-      @inbounds _A[i, j] = zero(T)
+    isempty(A) && return A
+    @kernel function triu_kernel!(_A, _d)
+        I = @index(Global, Cartesian)
+        i, j = Tuple(I)
+        if j < i + _d
+            @inbounds _A[i, j] = zero(T)
+        end
     end
-  end
-  triu_kernel!(get_backend(A))(A, d; ndrange = size(A))
-  return A
+    triu_kernel!(get_backend(A))(A, d; ndrange = size(A))
+    return A
 end
 
 # check if upper triangular starting from the kth superdiagonal.

test/testsuite/construction.jl

@@ -188,6 +188,16 @@
             @test Array(x1) ≈ x
         end
 
+        @testset "empty" begin
+            x = Matrix{Float32}(I, (0, 3))
+            x1 = AT{Float32, 2}(I, (0, 3))
+
+            @test Array(x1) ≈ x
+
+            copyto!(x1, I)
+            @test Array(x1) ≈ x
+        end
+
         @testset "JuliaGPU/GPUArrays.jl#439" begin
             x = AT{Float32}(I, 500, 300)
             y = Array{Float32}(I, 500, 300)

test/testsuite/linalg.jl

@@ -307,10 +307,13 @@
             @test_throws SingularException ldiv!(D, B)
         end
 
-        @testset "$f! with diagonal $d" for (f, f!) in ((triu, triu!), (tril, tril!)),
+        @testset "$f with diagonal $d" for f in (triu, triu!, tril, tril!),
                                             d in -2:2
             A = randn(Float32, 10, 10)
-            @test f(A, d) == Array(f!(AT(A), d))
+            @test compare(f, AT, A)
+
+            A_empty = randn(Float32, 0, 0)
+            @test compare(f, AT, A_empty)
         end
     end