optimizer: eliminate `isdefined` check #44708

aviatesk · 2022-03-23T12:53:38Z

This PR is based on #44706 and consists of two separate commits.
The primary change is the first commit (e205e50),
which implements additional isdefined-elimination pass within sroa_mutables!,
and the second commit (1f7dda1) does some refactoring on top of the first change.
EDIT: now this PR only implements the first commit, and the second commit is put off to another PR.

Their commit messages follow:

optimizer: add additional `isdefined`-elimination pass within `sroa_mutables!`

This commit implements a simple optimization within sroa_mutables! to
eliminate isdefined call by checking load-forwardability of the field.
This optimization may be especially useful to eliminate extra allocation
of Core.Box involved with a capturing closure, e.g.:

julia> callit(f, args...) = f(args...);

julia> function isdefined_elim()
           local arr::Vector{Any}
           callit() do
               arr = Any[]
           end
           return arr
       end;

julia> code_typed(isdefined_elim)

diff --git a/_master.jl b/_pr.jl
index 3aa40ba20e5..11eccf65f32 100644
--- a/_master.jl
+++ b/_pr.jl
@@ -1,15 +1,8 @@
 1-element Vector{Any}:
  CodeInfo(
-1 ─ %1  = Core.Box::Type{Core.Box}
-│   %2  = %new(%1)::Core.Box
-│   %3  = $(Expr(:foreigncall, :(:jl_alloc_array_1d), Vector{Any}, svec(Any, Int64), 0, :(:ccall), Vector{Any}, 0, 0))::Vector{Any}
-│         Core.setfield!(%2, :contents, %3)::Vector{Any}
-│   %5  = Core.isdefined(%2, :contents)::Bool
-└──       goto https://github.com/JuliaLang/julia/issues/3 if not %5
-2 ─       goto https://github.com/JuliaLang/julia/issues/4
-3 ─       $(Expr(:throw_undef_if_not, :arr, false))::Any
-4 ┄ %9  = Core.getfield(%2, :contents)::Any
-│         Core.typeassert(%9, Vector{Any})::Vector{Any}
-│   %11 = π (%9, Vector{Any})
-└──       return %11
+1 ─ %1 = $(Expr(:foreigncall, :(:jl_alloc_array_1d), Vector{Any}, svec(Any, Int64), 0, :(:ccall), Vector{Any}, 0, 0))::Vector{Any}
+└──      goto https://github.com/JuliaLang/julia/issues/3 if not true
+2 ─      goto https://github.com/JuliaLang/julia/issues/4
+3 ─      $(Expr(:throw_undef_if_not, :arr, false))::Any
+4 ┄      return %1
 ) => Vector{Any}

optimizer: switch to more general data structure of `SSADefUse`

Now (du::SSADefUse).uses field can contain arbitrary "usages" to be eliminated.
This structure might be helpful for implementing array SROA, for example.
Also slightly tweaks the implementation of ccall preserve elimination.

EDIT: will not be merged in this PR.

KristofferC · 2022-03-23T13:10:29Z

-└──       goto https://github.com/JuliaLang/julia/issues/3 if not %5
-2 ─       goto https://github.com/JuliaLang/julia/issues/4

Hmm 😄

vtjnash

The first commit SGTM. The second one seems to be a whole lot more allocations, and I question the value of it. I'd think a tag based system would be better, and avoid creating lots of random types to dispatch on just for tagging data with a kind.

This commit implements a simple optimization within `sroa_mutables!` to eliminate `isdefined` call by checking load-forwardability of the field. This optimization may be especially useful to eliminate extra allocation of `Core.Box` involved with a capturing closure, e.g.: ```julia julia> callit(f, args...) = f(args...); julia> function isdefined_elim() local arr::Vector{Any} callit() do arr = Any[] end return arr end; julia> code_typed(isdefined_elim) ``` ```diff diff --git a/_master.jl b/_pr.jl index 3aa40ba20e5..11eccf65f32 100644 --- a/_master.jl +++ b/_pr.jl @@ -1,15 +1,8 @@ 1-element Vector{Any}: CodeInfo( -1 ─ %1 = Core.Box::Type{Core.Box} -│ %2 = %new(%1)::Core.Box -│ %3 = $(Expr(:foreigncall, :(:jl_alloc_array_1d), Vector{Any}, svec(Any, Int64), 0, :(:ccall), Vector{Any}, 0, 0))::Vector{Any} -│ Core.setfield!(%2, :contents, %3)::Vector{Any} -│ %5 = Core.isdefined(%2, :contents)::Bool -└── goto #3 if not %5 -2 ─ goto #4 -3 ─ $(Expr(:throw_undef_if_not, :arr, false))::Any -4 ┄ %9 = Core.getfield(%2, :contents)::Any -│ Core.typeassert(%9, Vector{Any})::Vector{Any} -│ %11 = π (%9, Vector{Any}) -└── return %11 +1 ─ %1 = $(Expr(:foreigncall, :(:jl_alloc_array_1d), Vector{Any}, svec(Any, Int64), 0, :(:ccall), Vector{Any}, 0, 0))::Vector{Any} +└── goto #3 if not true +2 ─ goto #4 +3 ─ $(Expr(:throw_undef_if_not, :arr, false))::Any +4 ┄ return %1 ) => Vector{Any} ```

aviatesk · 2022-03-24T01:57:31Z

The second one seems to be a whole lot more allocations, and I question the value of it. I'd think a tag based system would be better, and avoid creating lots of random types to dispatch on just for tagging data with a kind.

Ok, let's go only with the first commit for now, and puts off the discussion on the second commit to another PR.

@inline

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 ```

@inline

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 ```

@inline

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 ```

aviatesk requested review from Keno and vtjnash March 23, 2022 12:54

aviatesk changed the title ~~optimizer: eliminate isdefined in sroa_mutables!~~ optimizer: eliminate isdefined check Mar 23, 2022

vtjnash reviewed Mar 23, 2022

View reviewed changes

Base automatically changed from avi/sroatest to master March 23, 2022 23:56

aviatesk force-pushed the avi/isdefinedelim branch from 1f7dda1 to 10cf29d Compare March 24, 2022 00:55

aviatesk merged commit e0c5e96 into master Mar 24, 2022

aviatesk deleted the avi/isdefinedelim branch March 24, 2022 03:00

aviatesk mentioned this pull request Mar 26, 2022

optimizer: eliminate more isdefined checks #44755

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optimizer: eliminate `isdefined` check #44708

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aviatesk commented Mar 23, 2022 •

edited

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aviatesk commented Mar 23, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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optimizer: add additional isdefined-elimination pass within sroa_mutables!

optimizer: switch to more general data structure of SSADefUse

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optimizer: eliminate `isdefined` check #44708

optimizer: eliminate `isdefined` check #44708

aviatesk commented Mar 23, 2022 •

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optimizer: add additional `isdefined`-elimination pass within `sroa_mutables!`

optimizer: switch to more general data structure of `SSADefUse`