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Use Ref(Ref(pair)) to force heap allocation #6

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Merged
merged 1 commit into from
May 15, 2021
Merged

Use Ref(Ref(pair)) to force heap allocation #6

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16 changes: 9 additions & 7 deletions src/dict.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -348,22 +348,24 @@ end

@inline value_ref(ref::RefSlotRef) = ImmutableRef(ref.ref[].value.x)

allocate_slot(::AbstractVector{Slot}) where {Slot<:Ref} = forceheap(Slot())
allocate_slot(::AbstractVector{Slot}) where {Slot<:Ref} = Ref(Slot())
# One indirection to force heap allocation

@inline function cas_slot!(
slotref::RefSlotRef{Slot},
new_slot::Slot,
new_slot_ref::Ref{Slot},
root,
key,
value,
) where {P,Slot<:Ref{P}}
ptr = slotref.ptr
new_slot = new_slot_ref[]
new_slot[] = value isa NoValue ? P(key) : P(key, value)
ou = UInt(pointer_from_objref(slotref.ref))
nu = UInt(pointer_from_objref(new_slot))
julia_write_barrier(new_slot)
julia_write_barrier(root, new_slot)
GC.@preserve new_slot begin
GC.@preserve new_slot_ref begin
ou = UInt(pointer_from_objref(slotref.ref))
nu = UInt(unsafe_load(Ptr{Ptr{Cvoid}}(pointer_from_objref(new_slot_ref))))
julia_write_barrier(new_slot)
julia_write_barrier(root, new_slot)
fu = UnsafeAtomics.cas!(Ptr{typeof(nu)}(ptr), ou, nu)
end
return fu == ou
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12 changes: 1 addition & 11 deletions src/utils.jl
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Expand Up @@ -166,24 +166,14 @@ end
end
end

const _FALSE_ = Ref(false)

# TODO: a teribble hack to force heap-allocation of `x`; can we get rid of it?
@inline function forceheap(x)
if _FALSE_[]
global SINK = x
end
return x
end

@generated function julia_write_barrier(args::Vararg{Any,N}) where {N}
pointer_exprs = map(1:N) do i
:(_pointer_from_objref(args[$i]))
end
jlp = "{} addrspace(10)*"
llvm_args = string.("%", 0:N-1)
word = "i$(Base.Sys.WORD_SIZE)"
entry_sig = join(word .* llvm_args, ", ")
entry_sig = join(word .* " " .* llvm_args, ", ")
ptrs = string.("%ptr", 0:N-1)
wb_sig = join("$jlp " .* ptrs, ", ")
inttoptr = join(
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