Fix Fix load and store for sizeof(T) == 0 (#16)

Author: vchuravy

Project.toml

@@ -1,7 +1,7 @@
 name = "UnsafeAtomicsLLVM"
 uuid = "d80eeb9a-aca5-4d75-85e5-170c8b632249"
 authors = ["Takafumi Arakaki <aka.tkf@gmail.com> and contributors"]
-version = "0.2.1"
+version = "0.2.2"
 
 [deps]
 LLVM = "929cbde3-209d-540e-8aea-75f648917ca0"

src/atomics.jl

@@ -191,9 +191,9 @@ end
     if sizeof(T) == 0
         # Mimicking what `Core.Intrinsics.atomic_pointerset` generates.
         # See: https://github.com/JuliaLang/julia/blob/v1.7.2/src/cgutils.cpp#L1570-L1572
-        is_stronger_than_monotonic(order) || return :ptr
         return quote
-            Core.Intrinsics.fence($(QuoteNode(order)))
+            is_stronger_than_monotonic(_valueof(order)) || return :ptr
+            Core.Intrinsics.atomic_fence(_valueof(order))
             ptr
         end
     end

test/runtests.jl

@@ -10,13 +10,18 @@ function check_default_ordering(T::Type)
     xs = T[rand(T), rand(T)]
     x1 = rand(T)
     x2 = rand(T)
+    check_default_ordering(xs, x1, x2)
+end
+
+function check_default_ordering(xs::AbstractArray{T}, x1::T, x2::T) where {T}
     @debug "xs=$(repr(xs)) x1=$(repr(x1)) x2=$(repr(x2))"
 
     ptr = llvmptr(xs, 1)
     GC.@preserve xs begin
         @test UnsafeAtomics.load(ptr) === xs[1]
         UnsafeAtomics.store!(ptr, x1)
         @test xs[1] === x1
+        sizeof(T) == 0 && return # CAS hangs on zero sized data...
         desired = (old = x1, success = true)
         @test UnsafeAtomics.cas!(ptr, x1, x2) === (old = x1, success = true)
         @test xs[1] === x2
@@ -37,6 +42,10 @@ function test_explicit_ordering(T::Type = UInt)
     xs = T[rand(T), rand(T)]
     x1 = rand(T)
     x2 = rand(T)
+    test_explicit_ordering(xs, x1, x2)
+end
+
+function test_explicit_ordering(xs::AbstractArray{T}, x1::T, x2::T) where {T}
     @debug "xs=$(repr(xs)) x1=$(repr(x1)) x2=$(repr(x2))"
 
     ptr = llvmptr(xs, 1)
@@ -45,6 +54,7 @@ function test_explicit_ordering(T::Type = UInt)
         @test UnsafeAtomics.load(ptr, acquire) === xs[1]
         UnsafeAtomics.store!(ptr, x1, release)
         @test xs[1] === x1
+        sizeof(T) == 0 && return # CAS hangs on zero sized data...
         desired = (old = x1, success = true)
         @test UnsafeAtomics.cas!(ptr, x1, x2, acq_rel, acquire) === desired
         @test xs[1] === x2
@@ -79,4 +89,10 @@ end
         check_default_ordering(T)
         test_explicit_ordering(T)
     end
+
+    @testset "Zero-sized types" begin
+        @test sizeof(Nothing) == 0
+        check_default_ordering([nothing, nothing], nothing, nothing)
+        test_explicit_ordering([nothing, nothing], nothing, nothing)
+    end
 end