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Allow constant propagation of mutables with const fields #58371

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Merged
merged 2 commits into from
May 22, 2025
Merged

Allow constant propagation of mutables with const fields #58371

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40ae2e5
Allow contant propagation of mutables with const fields
gbaraldi May 9, 2025
ceba08e
Add test
gbaraldi May 13, 2025
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5 changes: 3 additions & 2 deletions Compiler/src/abstractlattice.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -227,9 +227,10 @@ that should be forwarded along with constant propagation.
end
@nospecializeinfer function is_const_prop_profitable_arg(𝕃::ConstsLattice, @nospecialize t)
if isa(t, Const)
# don't consider mutable values useful constants
# don't consider mutable values useful constants unless they have const fields
val = t.val
return isa(val, Symbol) || isa(val, Type) || isa(val, Method) || isa(val, CodeInstance) || !ismutable(val)
return isa(val, Symbol) || isa(val, Type) || isa(val, Method) || isa(val, CodeInstance) ||
!ismutable(val) || (typeof(val).name.constfields != C_NULL)
Comment on lines +232 to +233
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What about mutable singletons? Something like:

mutable struct Singleton end

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IIRC those get folded via the type system already. I couldn't make a case where it didnt do it (I only saw this case here with scoped values)

end
isa(t, PartialTypeVar) && return false # this isn't forwardable
return is_const_prop_profitable_arg(widenlattice(𝕃), t)
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10 changes: 10 additions & 0 deletions Compiler/test/irpasses.jl
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Expand Up @@ -2111,3 +2111,13 @@ let src = code_typed1(()) do
end
@test count(iscall((src, isdefined)), src.code) == 0
end
# We should successfully fold the default values of a ScopedValue
const svalconstprop = ScopedValue(1)
foosvalconstprop() = svalconstprop[]

let src = code_typed1(foosvalconstprop, ())
function is_constfield_load(expr)
iscall((src, getfield))(expr) && expr.args[3] in (:(:has_default), :(:default))
end
@test count(is_constfield_load, src.code) == 0
end
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