Replace @require CUDA with using GPUArraysCore (#1272)

* require GPUArrays instead of CUDA

* more

* change to unconditionally load GPUArraysCore

* add GPUArrays dep

* trivial trigger commit

Author: mcabbott

Project.toml

@@ -10,6 +10,8 @@ DiffRules = "b552c78f-8df3-52c6-915a-8e097449b14b"
 Distributed = "8ba89e20-285c-5b6f-9357-94700520ee1b"
 FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
+GPUArrays = "0c68f7d7-f131-5f86-a1c3-88cf8149b2d7"  # not loaded, just a version bound
+GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
 IRTools = "7869d1d1-7146-5819-86e3-90919afe41df"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
@@ -31,6 +33,8 @@ ChainRulesTestUtils = "1"
 DiffRules = "1.4"
 FillArrays = "0.8, 0.9, 0.10, 0.11, 0.12, 0.13"
 ForwardDiff = "0.10"
+GPUArrays = "8.4.2"  # not loaded, just a version bound
+GPUArraysCore = "0.1.1"
 IRTools = "0.4.4"
 LogExpFunctions = "0.3.1"
 MacroTools = "0.5"

src/lib/broadcast.jl

@@ -253,43 +253,32 @@ end
   return y, bc_fwd_back
 end
 
-@init @require CUDA="052768ef-5323-5732-b1bb-66c8b64840ba" begin
+using GPUArraysCore  # replaces @require CUDA block, weird indenting to preserve git blame
 
-  const CuArrayStyle = CUDA.AbstractGPUArrayStyle
-
-  if isdefined(CUDA, :cufunc)  # CUDA < 3.0
-
-    @eval @adjoint broadcasted(::CuArrayStyle, f, args...) =
-      broadcast_forward(CUDA.cufunc(f), args...)
-
-  else # CUDA >= 3.0 -- don't need cufunc(f).
        # Ordinary broadcasting calls broadcast_forward anyway when certain its' safe,
        # so perhaps this can be deleted? Possible edge case here:
        # https://github.com/FluxML/Zygote.jl/pull/1018#issuecomment-873629415
+  @adjoint broadcasted(::AbstractGPUArrayStyle, f, args...) =
+    broadcast_forward(f, args...)
 
-    @eval @adjoint broadcasted(::CuArrayStyle, f, args...) =
-      broadcast_forward(f, args...)
-
-  end
-
-  @adjoint (::Type{T})(xs::Array) where {T <: CUDA.CuArray} =
+  @adjoint (::Type{T})(xs::Array) where {T <: AbstractGPUArray} =
     T(xs), Δ -> (convert(Array, Δ), )
 
-  @adjoint function sum(xs::CUDA.AbstractGPUArray; dims = :)
+  @adjoint function sum(xs::AbstractGPUArray; dims = :)
     placeholder = similar(xs)
     sum(xs, dims = dims), Δ -> (placeholder .= Δ,)
   end
 
   # Make sure sum(f, ::CuArray) uses broadcase through forward-mode defined above
   # Not the ChainRules.rrule which will use the Zygote.Context and thus not be GPU compatible
-  @adjoint function sum(f, xs::CUDA.AbstractGPUArray; kws...)
+  @adjoint function sum(f, xs::AbstractGPUArray; kws...)
     @assert !haskey(kws, :init) # TODO add init support (julia 1.6)
     return pullback(__context__, (f, xs) -> sum(f.(xs); kws...), f, xs)
   end
 
-  @adjoint function Base.convert(::Type{T}, xs::Array)  where {T<:CUDA.AbstractGPUArray}
+  @adjoint function Base.convert(::Type{T}, xs::Array)  where {T<:AbstractGPUArray}
     Base.convert(T, xs), Δ -> (nothing, Base.convert(Array, Δ),)
   end
 
-  @eval pull_block_vert(sz, Δ::CUDA.CuArray, A::Number) = CUDA.@allowscalar Δ[sz]
-end
+  pull_block_vert(sz, Δ::AbstractGPUArray, A::Number) = @allowscalar Δ[sz]
+