Is there a way to check for whether values are getting boxed/unboxed short of
looking at the llvm code? As an example, here’s a simple function that I
wouldn’t expect to need any boxes:
julia> function isnullptr{T}(x::Ptr{T})
x == Ptr{T}(0)
end
isnullptr (generic function with 1 method)
But when I look at it with `code_warntype` it shows a comparison between the
boxed versions of the pointers:
julia> code_warntype(isnullptr, (Ptr{Void}, ))
Variables:
x::Ptr{Void}
Body:
begin # none, line 2:
return (Base.box)(UInt64,x::Ptr{Void}) ===
(Base.box)(UInt64,(Base.box)(Ptr{Void},0))::Bool
end::Bool
But by the time the code gets generated I can rest easy that all is well:
julia> code_llvm(isnullptr, (Ptr{Void}, ))
define i1 @julia_isnullptr_21821(i8*) {
top:
%1 = icmp eq i8* %0, null
ret i1 %1
}
So in this case the end result was what I expected, but I’m currently trying to
debug some problems with a larger chunk of code and am not very llmv-literate,
so I’m wondering if there’s another way to check.
Interestingly, a more general zero-checker: iszero{T}(x::T) = x == T(0) doesn’t
show boxing in the code_warntype output if T is an Int, but does if it's
Ptr{Void} type, so maybe this is somewhat pointer-specific? Unfortunately the
code I’m looking at does a lot of pointer wrangling.
Thanks,
Spencer
