Nested if-else-end "hoisted" flips causes IRTools.Inner branch error

[mattxwang]

I ran into this problem when doing HW2 for 267A (and I feel like it's now far enough from the HW to post!).

Consider this minimum-reproducible example:

using Dice

function same_door(door)
  f = flip(0.5)
  if door == DistUInt8(0)
    if f DistUInt8(0) else DistUInt8(1) end
  else
    if f DistUInt8(1) else DistUInt8(0) end
  end
end

door = discrete(DistUInt8,[1/2, 1/2])

println(pr(@dice(same_door(door))))

This produces the following error:

ERROR: LoadError: Error compiling @dynamo Dice.DiceDyna on (typeof(same_door), DistUInt8):
AssertionError: length(branches(bl)) == 2
Stacktrace:
  [1] functionalbranches!(bl::Any, pr::Any, labels::Any)
    @ IRTools.Inner ~/.julia/packages/IRTools/jcpZw/src/passes/cps.jl:36
  [2] _functional(ir::Any, tree::Any, vars::Any, cs::Any)
    @ IRTools.Inner ~/.julia/packages/IRTools/jcpZw/src/passes/cps.jl:66
  [3] _functional(ir::Any, tree::Any)
    @ IRTools.Inner ~/.julia/packages/IRTools/jcpZw/src/passes/cps.jl:50
  [4] functional(ir::Any)
    @ IRTools.Inner ~/.julia/packages/IRTools/jcpZw/src/passes/cps.jl:70
  [5] macro expansion
    @ ~/.julia/packages/Dice/OfImS/src/dsl.jl:53 [inlined]
  [6] macro expansion
    @ ./timing.jl:463 [inlined]
  [7] macro expansion
    @ ~/.julia/packages/Dice/OfImS/src/dsl.jl:50 [inlined]
  [8] transform(::Type{Dice.DiceDyna}, ::Type, ::Vararg{Type})
    @ Dice ~/.julia/packages/IRTools/jcpZw/src/reflection/dynamo.jl:197
  [9] dynamo(::Any, ::Any, ::Any, ::Any, ::Vararg{Any})
    @ IRTools.Inner ~/.julia/packages/IRTools/jcpZw/src/reflection/dynamo.jl:79
 [10] #s61#154
    @ ~/.julia/packages/IRTools/jcpZw/src/reflection/dynamo.jl:186 [inlined]
 [11] var"#s61#154"(dyna::Any, args::Any)
    @ Dice ./none:0
 [12] (::Core.GeneratedFunctionStub)(::Any, ::Vararg{Any})
    @ Core ./boot.jl:582
 [13] DiceDyna
    @ ~/.julia/packages/Dice/OfImS/src/dsl.jl:28 [inlined]
 [14] (::Dice.DiceDyna)(args::var"#17#18")
    @ Dice ~/.julia/packages/IRTools/jcpZw/src/reflection/dynamo.jl:0
 [15] dice(f::Function)
    @ Dice ~/.julia/packages/Dice/OfImS/src/dsl.jl:20
 [16] top-level scope
    @ ~/.julia/packages/Dice/OfImS/src/dsl.jl:27
 [17] include(fname::String)
    @ Base.MainInclude ./client.jl:476
 [18] top-level scope
    @ REPL[5]:1
in expression starting at /Users/matt/Dice.jl/examples/mini.jl:14

However, if I replace the inner if-else-end with the ifelse() function, I don't encounter the error:

using Dice

function same_door(door)
  f = flip(0.5)
  if door == DistUInt8(0)
    ifelse(f, DistUInt8(0), DistUInt8(1))
  else
    ifelse(f, DistUInt8(1), DistUInt8(0))
  end
end

door = discrete(DistUInt8,[1/2, 1/2])

println(pr(@dice(same_door(door))))

DataStructures.DefaultDict{Any, Any, Float64}(0 => 0.5, 1 => 0.5)

other reproducibility details

I'm running:

• macOS 13.3.1 on an M1 Mac Pro
  • to resolve the "closures not supported on this platform", I'm running Julia with Rosetta
• Julia 1.8
• f9956fe

[guyvdbroeck]

I think it is this known bug: FluxML/IRTools.jl#100