Faster startup/smaller sysimg, excising Pkg (for now) #4
Conversation
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@JeffBezanson My PR doesn't seem to be considered (maybe because it's not in JuliaLang's PR list, and I'm actually not sure why it appeared here, all my previous PRs didn't, I use the GitHub editor). Well, except you mentioned in total time would be higher, i.e. eaten up when you actually use functionality not loaded here/at startup. But I'm not convinced. Code in pkgimages is serialized to machine code too by now, and if/assuming the same code is compiled just elsewhere then should be as fast to load later. Besides some of the code might actually never be needed. I would like I think we should just merge this to master, and see if any benchmark actually shows slowdown. |
This commit improves SROA pass by extending the `unswitchtupleunion`
optimization to handle the general parametric types, e.g.:
```julia
julia> struct A{T}
x::T
end;
julia> function foo(a1, a2, c)
t = c ? A(a1) : A(a2)
return getfield(t, :x)
end;
julia> only(Base.code_ircode(foo, (Int,Float64,Bool); optimize_until="SROA"))
```
> Before
```
2 1 ─ goto #3 if not _4 │
2 ─ %2 = %new(A{Int64}, _2)::A{Int64} │╻ A
└── goto #4 │
3 ─ %4 = %new(A{Float64}, _3)::A{Float64} │╻ A
4 ┄ %5 = φ (#2 => %2, #3 => %4)::Union{A{Float64}, A{Int64}} │
3 │ %6 = Main.getfield(%5, :x)::Union{Float64, Int64} │
└── return %6 │
=> Union{Float64, Int64}
```
> After
```
julia> only(Base.code_ircode(foo, (Int,Float64,Bool); optimize_until="SROA"))
2 1 ─ goto #3 if not _4 │
2 ─ nothing::A{Int64} │╻ A
└── goto #4 │
3 ─ nothing::A{Float64} │╻ A
4 ┄ %8 = φ (#2 => _2, #3 => _3)::Union{Float64, Int64} │
│ nothing::Union{A{Float64}, A{Int64}}
3 │ %6 = %8::Union{Float64, Int64} │
└── return %6 │
=> Union{Float64, Int64}
```
See: JuliaLang#50833 (comment)
It's 22% faster startup because the sysimage is 33% smaller.
With a minor breaking change it would be 30.2% faster and 37.5% smaller.