add ability to evaluate ssavalues and locals

[KristofferC]

1|debug>
In sin(x) at special/trig.jl:30
  3  │          Core.NewvarNode(:(n))
  4  │          absx = (abs)(x)
  5  │    %5  = absx
  6  │    %6  = ($(Expr(:static_parameter, 1)))(π)
> 7  │    %7  = (/)(%6, 4)
  8  │    %8  = (<)(%5, %7)
  9  └───       goto #6 if not %8
 10  2 ── %10 = absx
 11  │    %11 = (eps)($(Expr(:static_parameter, 1)))

About to run: (/)(3.141592653589793, 4)
1|julia> var"%5", var"%6"
(2.0, 3.141592653589793)

[timholy]

IIUC this makes slots available by their number but not their name, right?

julia> function summer(A)
           s = zero(eltype(A))
           for i in eachindex(A)
               s += A[i]
           end
           return s
       end
summer (generic function with 1 method)

julia> src = Base.uncompressed_ast(@which summer([1,2,3]))
CodeInfo(
    @ REPL[10]:2 within `summer'
1 ─ %1  = Main.eltype(A)
│         s = Main.zero(%1)
│   @ REPL[10]:3 within `summer'
│   %3  = Main.eachindex(A)
│         @_4 = Base.iterate(%3)
│   %5  = @_4 === nothing
│   %6  = Base.not_int(%5)
└──       goto #4 if not %6
2 ┄ %8  = @_4
│         i = Core.getfield(%8, 1)
│   %10 = Core.getfield(%8, 2)
│   @ REPL[10]:4 within `summer'
│   %11 = s
│   %12 = Base.getindex(A, i)
│         s = %11 + %12
│         @_4 = Base.iterate(%3, %10)
│   %15 = @_4 === nothing
│   %16 = Base.not_int(%15)
└──       goto #4 if not %16
3 ─       goto #2
    @ REPL[10]:6 within `summer'
4 ┄       return s
)

julia> src.slotnames
5-element Array{Symbol,1}:
 Symbol("#self#")
 :A
 :s
 Symbol("")
 :i

[KristofferC]

Yes, for their name you just evaluate with the local variable name, right? I was a bit unsure if I should include this but it seems easy enough and when you see e.g. @_4 = Base.iterate(%3, %10) in the lowered code, perhaps you just want to look at what @_4 contains.

[timholy]

Right, duh, you're saying this gets covered the other branch. Carry on 😄

[codecov-commenter]

Codecov Report

Merging #395 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #395      +/-   ##
==========================================
+ Coverage   87.65%   87.68%   +0.02%     
==========================================
  Files          11       11              
  Lines        2001     2005       +4     
==========================================
+ Hits         1754     1758       +4     
  Misses        247      247              

Impacted Files	Coverage Δ
src/utils.jl	84.74% <100.00%> (+0.20%)	⬆️

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