Handle non-const function in return_types special case

[yuyichao]

Fix #19641

[yuyichao]

@nanosoldier runbenchmarks(ALL, vs = ":master")

[Sacha0]

[nanosoldier]

Your benchmark job has completed - possible performance regressions were detected. A full report can be found here. cc @jrevels

[Sacha0]

I could not reproduce any of the possible regressions locally. Best!

[Sacha0]

Confirming the test case in #19633 (comment) succeeds on this branch:

julia> baz() = (a = 1; Base._return_type((x, y) -> x + y + a, Base.Broadcast.typestuple(eye(4), eye(4))))
baz (generic function with 1 method)

julia> baz()
Float64

julia> @code_warntype baz()
Variables:
  #self#::#baz
  a::Int64
  #3::##3#4{Int64}

Body:
  begin
      a::Int64 = 1
      SSAValue(0) = Base._return_type
      #3::##3#4{Int64} = $(Expr(:new, ##3#4{Int64}, :(a)))
      SSAValue(1) = #3::##3#4{Int64}
      $(Expr(:invoke, MethodInstance for eye(::Type{T}, ::Int64, ::Int64), :(Base.eye), :(Base.Float64), 4, 4))
      $(Expr(:invoke, MethodInstance for eye(::Type{T}, ::Int64, ::Int64), :(Base.eye), :(Base.Float64), 4, 4))
      SSAValue(2) = $(QuoteNode(Tuple{Float64,Float64}))
      return $(QuoteNode(Float64))
  end::Type{Float64}

Best!

[musm]

ldexp, frexp, exponent, and significand are notoriously noisy. The functions are evaluated on scalars and take a few ns to finish. BenchmarkTools locally has ns resolution on my local pc, but perhaps not on the benchmarking server

[jrevels]

BenchmarkTools locally has ns resolution on my local pc, but perhaps not on the benchmarking server

The latest BenchmarkTools tag has picosecond resolution (it will pretty-print in fractions of nanoseconds), but I still need to update Nanosoldier with that capability.

[Sacha0]

Confirming that the test cases I've written against the code mentioned in the related discourse thread succeed on this branch. Best!

[andyferris]

Is this backportable?

(@tkelman are there any backports planned for v0.5? we still haven't seen v0.5.1, but then again I haven't seen a lot of bugs either)

[yuyichao]

Rebased. AppVeyor failure is the intermittent libgit2 network issue..... @JeffBezanson @vtjnash

[yuyichao]

Ping @JeffBezanson @vtjnash