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optimizer: eliminate more isdefined checks
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Follows up #44708 -- in that PR I missed the most obvious optimization
opportunity, i.e. we can safely eliminate `isdefined` checks when all
fields are defined at allocation site.
This change allows us to eliminate capturing closure constructions when
the body and callsite of capture closure is available within a optimized
frame, e.g.:
```julia
function abmult(r::Int, x0)
    if r < 0
        r = -r
    end
    f = x -> x * r
    return @inline f(x0)
end
```
```diff
diff --git a/_master.jl b/_pr.jl
index ea06d865b75..c38f221090f 100644
--- a/_master.jl
+++ b/_pr.jl
@@ -1,24 +1,19 @@
 julia> @code_typed abmult(-3, 3)
 CodeInfo(
-1 ── %1  = Core.Box::Type{Core.Box}
-│    %2  = %new(%1, r@_2)::Core.Box
-│    %3  = Core.isdefined(%2, :contents)::Bool
-└───       goto #3 if not %3
+1 ──       goto #3 if not true
 2 ──       goto #4
 3 ──       $(Expr(:throw_undef_if_not, :r, false))::Any
-4 ┄─ %7  = (r@_2 < 0)::Any
-└───       goto #9 if not %7
-5 ── %9  = Core.isdefined(%2, :contents)::Bool
-└───       goto #7 if not %9
+4 ┄─ %4  = (r@_2 < 0)::Any
+└───       goto #9 if not %4
+5 ──       goto #7 if not true
 6 ──       goto #8
 7 ──       $(Expr(:throw_undef_if_not, :r, false))::Any
-8 ┄─ %13 = -r@_2::Any
-9 ┄─ %14 = φ (#4 => r@_2, #8 => %13)::Any
-│    %15 = Core.isdefined(%2, :contents)::Bool
-└───       goto #11 if not %15
+8 ┄─ %9  = -r@_2::Any
+9 ┄─ %10 = φ (#4 => r@_2, #8 => %9)::Any
+└───       goto #11 if not true
 10 ─       goto #12
 11 ─       $(Expr(:throw_undef_if_not, :r, false))::Any
-12 ┄ %19 = (x0 * %14)::Any
+12 ┄ %14 = (x0 * %10)::Any
 └───       goto #13
-13 ─       return %19
+13 ─       return %14
 ) => Any
```
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aviatesk committed Mar 26, 2022
1 parent 5dc6155 commit ccd2746
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Showing 2 changed files with 35 additions and 12 deletions.
22 changes: 10 additions & 12 deletions base/compiler/ssair/passes.jl
Original file line number Diff line number Diff line change
Expand Up @@ -372,10 +372,7 @@ function lift_leaves(compact::IncrementalCompact,
lift_arg!(compact, leaf, cache_key, def, 1+field, lifted_leaves)
continue
elseif isexpr(def, :new)
typ = widenconst(types(compact)[leaf])
if isa(typ, UnionAll)
typ = unwrap_unionall(typ)
end
typ = unwrap_unionall(widenconst(types(compact)[leaf]))
(isa(typ, DataType) && !isabstracttype(typ)) || return nothing
@assert !ismutabletype(typ)
if length(def.args) < 1+field
Expand Down Expand Up @@ -786,10 +783,7 @@ function sroa_pass!(ir::IRCode)
push!(preserved, preserved_arg.id)
continue
elseif isexpr(def, :new)
typ = widenconst(argextype(SSAValue(defidx), compact))
if isa(typ, UnionAll)
typ = unwrap_unionall(typ)
end
typ = unwrap_unionall(widenconst(argextype(SSAValue(defidx), compact)))
if typ isa DataType && !ismutabletype(typ)
record_immutable_preserve!(new_preserves, def, compact)
push!(preserved, preserved_arg.id)
Expand Down Expand Up @@ -948,10 +942,7 @@ function sroa_mutables!(ir::IRCode, defuses::IdDict{Int, Tuple{SPCSet, SSADefUse
defexpr = ir[SSAValue(idx)][:inst]
isexpr(defexpr, :new) || continue
newidx = idx
typ = ir.stmts[newidx][:type]
if isa(typ, UnionAll)
typ = unwrap_unionall(typ)
end
typ = unwrap_unionall(ir.stmts[newidx][:type])
# Could still end up here if we tried to setfield! on an immutable, which would
# error at runtime, but is not illegal to have in the IR.
ismutabletype(typ) || continue
Expand Down Expand Up @@ -1023,6 +1014,13 @@ function sroa_mutables!(ir::IRCode, defuses::IdDict{Int, Tuple{SPCSet, SSADefUse
end
has_safe_def(ir, get_domtree(), allblocks, du, newidx, use.idx) || @goto skip
end
else # always have some definition at the allocation site
for i = 1:length(du.uses)
use = du.uses[i]
if use.kind === :isdefined
ir[SSAValue(use.idx)][:inst] = true
end
end
end
end
# Everything accounted for. Go field by field and perform idf:
Expand Down
25 changes: 25 additions & 0 deletions test/compiler/irpasses.jl
Original file line number Diff line number Diff line change
Expand Up @@ -493,6 +493,31 @@ let src = code_typed1(isdefined_elim)
end
@test isdefined_elim() == Any[]

function abmult(r::Int, x0)
if r < 0
r = -r
end
f = x -> x * r
return @inline f(x0)
end
let src = code_typed1(abmult, (Int,Int))
@test is_scalar_replaced(src)
end
@test abmult(-3, 3) == 9

function abmult2(r0::Int, x0)
r::Int = r0
if r < 0
r = -r
end
f = x -> x * r
return f(x0)
end
let src = code_typed1(abmult2, (Int,Int))
@test is_scalar_replaced(src)
end
@test abmult2(-3, 3) == 9

# comparison lifting
# ==================

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