# Different compilation results for global and "local" functions

**URL:** <https://discourse.julialang.org/t/different-compilation-results-for-global-and-local-functions/3802>\
**Category:** New to Julia\
**Created:** [May 19, 2017, 8:50am UTC](https://discourse.julialang.org/t/different-compilation-results-for-global-and-local-functions/3802 "2017-05-19T08:50:39Z")\
**Posts on this page:** 1\
**Showing post:** 7

<div class="post-metadata">

**Author:** ![yuyichao](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yuyichao/32/20_2.png) [@yuyichao](https://discourse.julialang.org/u/yuyichao)\
**Post date:** [May 20, 2017, 9:57pm UTC](https://discourse.julialang.org/t/different-compilation-results-for-global-and-local-functions/3802/7 "2017-05-20T21:57:56Z")

</div>

Do **NOT** use `code_llvm` as your first tool to identify performance issue. I really don’t know who started the tradition of using overkilling tools to confuse themselves (certainly not you) but this has cause too many people to look at low level representation and trying to guess what it means and confuse more people in that process (and I expect you to be one of the victims too).

In particular, do not use `code_llvm` if you have not used LLVM IR before and do not suggest it to anyone unless you can understand it yourself or at least identify the issue in a particular IR. It’s much better than `code_native` (which is almost never useful for performance issues) but we still have much better tools in most of the case.

In almost all cases, the right starting point is `code_warntype`. In this case,

```julia
julia> @code_warntype compute(1)
Variables:                                                                                          
  #self#::#compute                                                                                  
  k::Int64                                                                                          
  i::Int64                                                                                          
  #temp#::Int64                                                                                     
  s::Int64                                                                                          

Body:
  begin
      s::Int64 = 2 # line 5:
      SSAValue(3) = (Base.select_value)((Base.sle_int)(1, 1000)::Bool, 1000, (Base.sub_int)(1, 1)::Int64)::Int64
      #temp#::Int64 = 1
      5:
      unless (Base.not_int)((#temp#::Int64 === (Base.add_int)(SSAValue(3), 1)::Int64)::Bool)::Bool goto 14
      SSAValue(4) = #temp#::Int64
      SSAValue(5) = (Base.add_int)(#temp#::Int64, 1)::Int64
      #temp#::Int64 = SSAValue(5) # line 6:
      s::Int64 = (Base.add_int)(s::Int64, k::Int64)::Int64
      12:
      goto 5
      14: # line 8:
      SSAValue(2) = s::Int64
      (Core.setfield!)(Core.Box(0), :contents, SSAValue(2))::Int64 # line 9:
      return
  end::Void

julia> @code_warntype compute2(1)
Variables:
  #self#::#local_compute#1
  k::Int64
  i::Int64
  #temp#::Int64
  s::Int64

Body:
  begin
      s::Int64 = 2 # line 13:
      SSAValue(3) = (Base.select_value)((Base.sle_int)(1, 1000)::Bool, 1000, (Base.sub_int)(1, 1)::Int64)::Int64
      #temp#::Int64 = 1
      5:
      unless (Base.not_int)((#temp#::Int64 === (Base.add_int)(SSAValue(3), 1)::Int64)::Bool)::Bool goto 14
      SSAValue(4) = #temp#::Int64
      SSAValue(5) = (Base.add_int)(#temp#::Int64, 1)::Int64
      #temp#::Int64 = SSAValue(5) # line 14:
      s::Int64 = (Base.add_int)(s::Int64, k::Int64)::Int64
      12:
      goto 5
      14: # line 16:
      SSAValue(2) = s::Int64
      (Core.setfield!)((Core.getfield)(#self#::#local_compute#1, :result)::Any, :contents, SSAValue(2))::Int64 # line 17:
      return
  end::Void

```

I’ll not expect all users to identify this is related to closure lowering but it should be very clear what the difference is in the IR (the last expression) and the slower version also warns you about a `::Any` type.

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_[View the full topic](https://discourse.julialang.org/t/different-compilation-results-for-global-and-local-functions/3802)._