Implement write barrier fastpath for sticky immix #8
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This is part of the work to address JuliaLang#51352 by attempting to allow the compiler to perform SRAO on persistent data structures like `PersistentDict` as if they were regular immutable data structures. These sorts of data structures have very complicated internals (with lots of mutation, memory sharing, etc.), but a relatively simple interface. As such, it is unlikely that our compiler will have sufficient power to optimize this interface by analyzing the implementation. We thus need to come up with some other mechanism that gives the compiler license to perform the requisite optimization. One way would be to just hardcode `PersistentDict` into the compiler, optimizing it like any of the other builtin datatypes. However, this is of course very unsatisfying. At the other end of the spectrum would be something like a generic rewrite rule system (e-graphs anyone?) that would let the PersistentDict implementation declare its interface to the compiler and the compiler would use this for optimization (in a perfect world, the actual rewrite would then be checked using some sort of formal methods). I think that would be interesting, but we're very far from even being able to design something like that (at least in Base - experiments with external AbstractInterpreters in this direction are encouraged). This PR tries to come up with a reasonable middle ground, where the compiler gets some knowledge of the protocol hardcoded without having to know about the implementation details of the data structure. The basic ideas is that `Core` provides some magic generic functions that implementations can extend. Semantically, they are not special. They dispatch as usual, and implementations are expected to work properly even in the absence of any compiler optimizations. However, the compiler is semantically permitted to perform structural optimization using these magic generic functions. In the concrete case, this PR introduces the `KeyValue` interface which consists of two generic functions, `get` and `set`. The core optimization is that the compiler is allowed to rewrite any occurrence of `get(set(x, k, v), k)` into `v` without additional legality checks. In particular, the compiler performs no type checks, conversions, etc. The higher level implementation code is expected to do all that. This approach closely matches the general direction we've been taking in external AbstractInterpreters for embedding additional semantics and optimization opportunities into Julia code (although we generally use methods there, rather than full generic functions), so I think we have some evidence that this sort of approach works reasonably well. Nevertheless, this is certainly an experiment and the interface is explicitly declared unstable. ## Current Status This is fully working and implemented, but the optimization currently bails on anything but the simplest cases. Filling all those cases in is not particularly hard, but should be done along with a more invasive refactoring of SROA, so we should figure out the general direction here first and then we can finish all that up in a follow-up cleanup. ## Obligatory benchmark Before: ``` julia> using BenchmarkTools julia> function foo() a = Base.PersistentDict(:a => 1) return a[:a] end foo (generic function with 1 method) julia> @benchmark foo() BenchmarkTools.Trial: 10000 samples with 993 evaluations. Range (min … max): 32.940 ns … 28.754 μs ┊ GC (min … max): 0.00% … 99.76% Time (median): 49.647 ns ┊ GC (median): 0.00% Time (mean ± σ): 57.519 ns ± 333.275 ns ┊ GC (mean ± σ): 10.81% ± 2.22% ▃█▅ ▁▃▅▅▃▁ ▁▃▂ ▂ ▁▂▄▃▅▇███▇▃▁▂▁▁▁▁▁▁▁▁▂▂▅██████▅▂▁▁▁▁▁▁▁▁▁▁▂▃▃▇███▇▆███▆▄▃▃▂▂ ▃ 32.9 ns Histogram: frequency by time 68.6 ns < Memory estimate: 128 bytes, allocs estimate: 4. julia> @code_typed foo() CodeInfo( 1 ─ %1 = invoke Vector{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}}(Base.HashArrayMappedTries.undef::UndefInitializer, 1::Int64)::Vector{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}} │ %2 = %new(Base.HashArrayMappedTries.HAMT{Symbol, Int64}, %1, 0x00000000)::Base.HashArrayMappedTries.HAMT{Symbol, Int64} │ %3 = %new(Base.HashArrayMappedTries.Leaf{Symbol, Int64}, :a, 1)::Base.HashArrayMappedTries.Leaf{Symbol, Int64} │ %4 = Base.getfield(%2, :data)::Vector{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}} │ %5 = $(Expr(:boundscheck, true))::Bool └── goto mmtk#5 if not %5 2 ─ %7 = Base.sub_int(1, 1)::Int64 │ %8 = Base.bitcast(UInt64, %7)::UInt64 │ %9 = Base.getfield(%4, :size)::Tuple{Int64} │ %10 = $(Expr(:boundscheck, true))::Bool │ %11 = Base.getfield(%9, 1, %10)::Int64 │ %12 = Base.bitcast(UInt64, %11)::UInt64 │ %13 = Base.ult_int(%8, %12)::Bool └── goto mmtk#4 if not %13 3 ─ goto mmtk#5 4 ─ %16 = Core.tuple(1)::Tuple{Int64} │ invoke Base.throw_boundserror(%4::Vector{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}}, %16::Tuple{Int64})::Union{} └── unreachable 5 ┄ %19 = Base.getfield(%4, :ref)::MemoryRef{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}} │ %20 = Base.memoryref(%19, 1, false)::MemoryRef{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}} │ Base.memoryrefset!(%20, %3, :not_atomic, false)::MemoryRef{Union{Base.HashArrayMappedTries.HAMT{Symbol, Int64}, Base.HashArrayMappedTries.Leaf{Symbol, Int64}}} └── goto mmtk#6 6 ─ %23 = Base.getfield(%2, :bitmap)::UInt32 │ %24 = Base.or_int(%23, 0x00010000)::UInt32 │ Base.setfield!(%2, :bitmap, %24)::UInt32 └── goto mmtk#7 7 ─ %27 = %new(Base.PersistentDict{Symbol, Int64}, %2)::Base.PersistentDict{Symbol, Int64} └── goto mmtk#8 8 ─ %29 = invoke Base.getindex(%27::Base.PersistentDict{Symbol, Int64},🅰️ :Symbol)::Int64 └── return %29 ``` After: ``` julia> using BenchmarkTools julia> function foo() a = Base.PersistentDict(:a => 1) return a[:a] end foo (generic function with 1 method) julia> @benchmark foo() BenchmarkTools.Trial: 10000 samples with 1000 evaluations. Range (min … max): 2.459 ns … 11.320 ns ┊ GC (min … max): 0.00% … 0.00% Time (median): 2.460 ns ┊ GC (median): 0.00% Time (mean ± σ): 2.469 ns ± 0.183 ns ┊ GC (mean ± σ): 0.00% ± 0.00% ▂ █ ▁ █ ▂ █▁▁▁▁█▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█▁▁▁▁█ █ 2.46 ns Histogram: log(frequency) by time 2.47 ns < Memory estimate: 0 bytes, allocs estimate: 0. julia> @code_typed foo() CodeInfo( 1 ─ return 1 ```
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`@something` eagerly unwraps any `Some` given to it, while keeping the
variable between its arguments the same. This can be an issue if a
previously unpacked value is used as input to `@something`, leading to a
type instability on more than two arguments (e.g. because of a fallback
to `Some(nothing)`). By using different variables for each argument,
type inference has an easier time handling these cases that are isolated
to single branches anyway.
This also adds some comments to the macro, since it's non-obvious what
it does.
Benchmarking the specific case I encountered this in led to a ~2x
performance improvement on multiple machines.
1.10-beta3/master:
```
[sukera@tower 01]$ jl1100 -q --project=. -L 01.jl -e 'bench()'
v"1.10.0-beta3"
BenchmarkTools.Trial: 10000 samples with 1 evaluation.
Range (min … max): 38.670 μs … 70.350 μs ┊ GC (min … max): 0.00% … 0.00%
Time (median): 43.340 μs ┊ GC (median): 0.00%
Time (mean ± σ): 43.395 μs ± 1.518 μs ┊ GC (mean ± σ): 0.00% ± 0.00%
▆█▂ ▁▁
▂▂▂▂▂▂▂▂▂▁▂▂▂▃▃▃▂▂▃▃▃▂▂▂▂▂▄▇███▆██▄▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂ ▃
38.7 μs Histogram: frequency by time 48 μs <
Memory estimate: 0 bytes, allocs estimate: 0.
```
This PR:
```
[sukera@tower 01]$ julia -q --project=. -L 01.jl -e 'bench()'
v"1.11.0-DEV.970"
BenchmarkTools.Trial: 10000 samples with 1 evaluation.
Range (min … max): 22.820 μs … 44.980 μs ┊ GC (min … max): 0.00% … 0.00%
Time (median): 24.300 μs ┊ GC (median): 0.00%
Time (mean ± σ): 24.370 μs ± 832.239 ns ┊ GC (mean ± σ): 0.00% ± 0.00%
▂▅▇██▇▆▅▁
▂▂▂▂▂▂▂▂▃▃▄▅▇███████████▅▄▃▃▂▂▂▂▂▂▂▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▂▂ ▃
22.8 μs Histogram: frequency by time 27.7 μs <
Memory estimate: 0 bytes, allocs estimate: 0.
```
<details>
<summary>Benchmarking code (spoilers for Advent Of Code 2023 Day 01,
Part 01). Running this requires the input of that Advent Of Code
day.</summary>
```julia
using BenchmarkTools
using InteractiveUtils
isdigit(d::UInt8) = UInt8('0') <= d <= UInt8('9')
someDigit(c::UInt8) = isdigit(c) ? Some(c - UInt8('0')) : nothing
function part1(data)
total = 0
may_a = nothing
may_b = nothing
for c in data
digitRes = someDigit(c)
may_a = @something may_a digitRes Some(nothing)
may_b = @something digitRes may_b Some(nothing)
if c == UInt8('\n')
digit_a = may_a::UInt8
digit_b = may_b::UInt8
total += digit_a*0xa + digit_b
may_a = nothing
may_b = nothing
end
end
return total
end
function bench()
data = read("input.txt")
display(VERSION)
println()
display(@benchmark part1($data))
nothing
end
```
</details>
<details>
<summary>`@code_warntype` before</summary>
```julia
julia> @code_warntype part1(data)
MethodInstance for part1(::Vector{UInt8})
from part1(data) @ Main ~/Documents/projects/AOC/2023/01/01.jl:7
Arguments
#self#::Core.Const(part1)
data::Vector{UInt8}
Locals
@_3::Union{Nothing, Tuple{UInt8, Int64}}
may_b::Union{Nothing, UInt8}
may_a::Union{Nothing, UInt8}
total::Int64
c::UInt8
digit_b::UInt8
digit_a::UInt8
val@_10::Any
val@_11::Any
digitRes::Union{Nothing, Some{UInt8}}
@_13::Union{Some{Nothing}, Some{UInt8}, UInt8}
@_14::Union{Some{Nothing}, Some{UInt8}}
@_15::Some{Nothing}
@_16::Union{Some{Nothing}, Some{UInt8}, UInt8}
@_17::Union{Some{Nothing}, UInt8}
@_18::Some{Nothing}
Body::Int64
1 ── (total = 0)
│ (may_a = Main.nothing)
│ (may_b = Main.nothing)
│ %4 = data::Vector{UInt8}
│ (@_3 = Base.iterate(%4))
│ %6 = (@_3 === nothing)::Bool
│ %7 = Base.not_int(%6)::Bool
└─── goto mmtk#24 if not %7
2 ┄─ Core.NewvarNode(:(digit_b))
│ Core.NewvarNode(:(digit_a))
│ Core.NewvarNode(:(val@_10))
│ %12 = @_3::Tuple{UInt8, Int64}
│ (c = Core.getfield(%12, 1))
│ %14 = Core.getfield(%12, 2)::Int64
│ (digitRes = Main.someDigit(c))
│ (val@_11 = may_a)
│ %17 = (val@_11::Union{Nothing, UInt8} !== Base.nothing)::Bool
└─── goto mmtk#4 if not %17
3 ── (@_13 = val@_11::UInt8)
└─── goto mmtk#11
4 ── (val@_11 = digitRes)
│ %22 = (val@_11::Union{Nothing, Some{UInt8}} !== Base.nothing)::Bool
└─── goto mmtk#6 if not %22
5 ── (@_14 = val@_11::Some{UInt8})
└─── goto mmtk#10
6 ── (val@_11 = Main.Some(Main.nothing))
│ %27 = (val@_11::Core.Const(Some(nothing)) !== Base.nothing)::Core.Const(true)
└─── goto mmtk#8 if not %27
7 ── (@_15 = val@_11::Core.Const(Some(nothing)))
└─── goto mmtk#9
8 ── Core.Const(:(@_15 = Base.nothing))
9 ┄─ (@_14 = @_15)
10 ┄ (@_13 = @_14)
11 ┄ %34 = @_13::Union{Some{Nothing}, Some{UInt8}, UInt8}
│ (may_a = Base.something(%34))
│ (val@_10 = digitRes)
│ %37 = (val@_10::Union{Nothing, Some{UInt8}} !== Base.nothing)::Bool
└─── goto mmtk#13 if not %37
12 ─ (@_16 = val@_10::Some{UInt8})
└─── goto mmtk#20
13 ─ (val@_10 = may_b)
│ %42 = (val@_10::Union{Nothing, UInt8} !== Base.nothing)::Bool
└─── goto mmtk#15 if not %42
14 ─ (@_17 = val@_10::UInt8)
└─── goto mmtk#19
15 ─ (val@_10 = Main.Some(Main.nothing))
│ %47 = (val@_10::Core.Const(Some(nothing)) !== Base.nothing)::Core.Const(true)
└─── goto mmtk#17 if not %47
16 ─ (@_18 = val@_10::Core.Const(Some(nothing)))
└─── goto mmtk#18
17 ─ Core.Const(:(@_18 = Base.nothing))
18 ┄ (@_17 = @_18)
19 ┄ (@_16 = @_17)
20 ┄ %54 = @_16::Union{Some{Nothing}, Some{UInt8}, UInt8}
│ (may_b = Base.something(%54))
│ %56 = c::UInt8
│ %57 = Main.UInt8('\n')::Core.Const(0x0a)
│ %58 = (%56 == %57)::Bool
└─── goto mmtk#22 if not %58
21 ─ (digit_a = Core.typeassert(may_a, Main.UInt8))
│ (digit_b = Core.typeassert(may_b, Main.UInt8))
│ %62 = total::Int64
│ %63 = (digit_a * 0x0a)::UInt8
│ %64 = (%63 + digit_b)::UInt8
│ (total = %62 + %64)
│ (may_a = Main.nothing)
└─── (may_b = Main.nothing)
22 ┄ (@_3 = Base.iterate(%4, %14))
│ %69 = (@_3 === nothing)::Bool
│ %70 = Base.not_int(%69)::Bool
└─── goto mmtk#24 if not %70
23 ─ goto mmtk#2
24 ┄ return total
```
</details>
<details>
<summary>`@code_native debuginfo=:none` Before </summary>
```julia
julia> @code_native debuginfo=:none part1(data)
.text
.file "part1"
.globl julia_part1_418 # -- Begin function julia_part1_418
.p2align 4, 0x90
.type julia_part1_418,@function
julia_part1_418: # @julia_part1_418
# %bb.0: # %top
push rbp
mov rbp, rsp
push r15
push r14
push r13
push r12
push rbx
sub rsp, 40
mov rax, qword ptr [rdi + 8]
test rax, rax
je .LBB0_1
# %bb.2: # %L17
mov rcx, qword ptr [rdi]
dec rax
mov r10b, 1
xor r14d, r14d
# implicit-def: $r12b
# implicit-def: $r13b
# implicit-def: $r9b
# implicit-def: $sil
mov qword ptr [rbp - 64], rax # 8-byte Spill
mov al, 1
mov dword ptr [rbp - 48], eax # 4-byte Spill
# implicit-def: $al
# kill: killed $al
xor eax, eax
mov qword ptr [rbp - 56], rax # 8-byte Spill
mov qword ptr [rbp - 72], rcx # 8-byte Spill
# implicit-def: $cl
jmp .LBB0_3
.p2align 4, 0x90
.LBB0_8: # in Loop: Header=BB0_3 Depth=1
mov dword ptr [rbp - 48], 0 # 4-byte Folded Spill
.LBB0_24: # %post_union_move
# in Loop: Header=BB0_3 Depth=1
movzx r13d, byte ptr [rbp - 41] # 1-byte Folded Reload
mov r12d, r8d
cmp qword ptr [rbp - 64], r14 # 8-byte Folded Reload
je .LBB0_13
.LBB0_25: # %guard_exit113
# in Loop: Header=BB0_3 Depth=1
inc r14
mov r10d, ebx
.LBB0_3: # %L19
# =>This Inner Loop Header: Depth=1
mov rax, qword ptr [rbp - 72] # 8-byte Reload
xor ebx, ebx
xor edi, edi
movzx r15d, r9b
movzx ecx, cl
movzx esi, sil
mov r11b, 1
# implicit-def: $r9b
movzx edx, byte ptr [rax + r14]
lea eax, [rdx - 58]
lea r8d, [rdx - 48]
cmp al, -10
setae bl
setb dil
test r10b, 1
cmovne r15d, edi
mov edi, 0
cmovne ecx, ebx
mov bl, 1
cmovne esi, edi
test r15b, 1
jne .LBB0_7
# %bb.4: # %L76
# in Loop: Header=BB0_3 Depth=1
mov r11b, 2
test cl, 1
jne .LBB0_5
# %bb.6: # %L78
# in Loop: Header=BB0_3 Depth=1
mov ebx, r10d
mov r9d, r15d
mov byte ptr [rbp - 41], r13b # 1-byte Spill
test sil, 1
je .LBB0_26
.LBB0_7: # %L82
# in Loop: Header=BB0_3 Depth=1
cmp al, -11
jbe .LBB0_9
jmp .LBB0_8
.p2align 4, 0x90
.LBB0_5: # in Loop: Header=BB0_3 Depth=1
mov ecx, r8d
mov sil, 1
xor ebx, ebx
mov byte ptr [rbp - 41], r8b # 1-byte Spill
xor r9d, r9d
xor ecx, ecx
cmp al, -11
ja .LBB0_8
.LBB0_9: # %L90
# in Loop: Header=BB0_3 Depth=1
test byte ptr [rbp - 48], 1 # 1-byte Folded Reload
jne .LBB0_23
# %bb.10: # %L115
# in Loop: Header=BB0_3 Depth=1
cmp dl, 10
jne .LBB0_11
# %bb.14: # %L122
# in Loop: Header=BB0_3 Depth=1
test r15b, 1
jne .LBB0_15
# %bb.12: # %L130.thread
# in Loop: Header=BB0_3 Depth=1
movzx eax, byte ptr [rbp - 41] # 1-byte Folded Reload
mov bl, 1
add eax, eax
lea eax, [rax + 4*rax]
add al, r12b
movzx eax, al
add qword ptr [rbp - 56], rax # 8-byte Folded Spill
mov al, 1
mov dword ptr [rbp - 48], eax # 4-byte Spill
cmp qword ptr [rbp - 64], r14 # 8-byte Folded Reload
jne .LBB0_25
jmp .LBB0_13
.p2align 4, 0x90
.LBB0_23: # %L115.thread
# in Loop: Header=BB0_3 Depth=1
mov al, 1
# implicit-def: $r8b
mov dword ptr [rbp - 48], eax # 4-byte Spill
cmp dl, 10
jne .LBB0_24
jmp .LBB0_21
.LBB0_11: # in Loop: Header=BB0_3 Depth=1
mov r8d, r12d
jmp .LBB0_24
.LBB0_1:
xor eax, eax
mov qword ptr [rbp - 56], rax # 8-byte Spill
.LBB0_13: # %L159
mov rax, qword ptr [rbp - 56] # 8-byte Reload
add rsp, 40
pop rbx
pop r12
pop r13
pop r14
pop r15
pop rbp
ret
.LBB0_21: # %L122.thread
test r15b, 1
jne .LBB0_15
# %bb.22: # %post_box_union58
movabs rdi, offset .L_j_str1
movabs rax, offset ijl_type_error
movabs rsi, 140008511215408
movabs rdx, 140008667209736
call rax
.LBB0_15: # %fail
cmp r11b, 1
je .LBB0_19
# %bb.16: # %fail
movzx eax, r11b
cmp eax, 2
jne .LBB0_17
# %bb.20: # %box_union54
movzx eax, byte ptr [rbp - 41] # 1-byte Folded Reload
movabs rcx, offset jl_boxed_uint8_cache
mov rdx, qword ptr [rcx + 8*rax]
jmp .LBB0_18
.LBB0_26: # %L80
movabs rax, offset ijl_throw
movabs rdi, 140008495049392
call rax
.LBB0_19: # %box_union
movabs rdx, 140008667209736
jmp .LBB0_18
.LBB0_17:
xor edx, edx
.LBB0_18: # %post_box_union
movabs rdi, offset .L_j_str1
movabs rax, offset ijl_type_error
movabs rsi, 140008511215408
call rax
.Lfunc_end0:
.size julia_part1_418, .Lfunc_end0-julia_part1_418
# -- End function
.type .L_j_str1,@object # @_j_str1
.section .rodata.str1.1,"aMS",@progbits,1
.L_j_str1:
.asciz "typeassert"
.size .L_j_str1, 11
.section ".note.GNU-stack","",@progbits
```
</details>
<details>
<summary>`@code_warntype` After</summary>
```julia
[sukera@tower 01]$ julia -q --project=. -L 01.jl
julia> data = read("input.txt");
julia> @code_warntype part1(data)
MethodInstance for part1(::Vector{UInt8})
from part1(data) @ Main ~/Documents/projects/AOC/2023/01/01.jl:7
Arguments
#self#::Core.Const(part1)
data::Vector{UInt8}
Locals
@_3::Union{Nothing, Tuple{UInt8, Int64}}
may_b::Union{Nothing, UInt8}
may_a::Union{Nothing, UInt8}
total::Int64
val@_7::Union{}
val@_8::Union{}
c::UInt8
digit_b::UInt8
digit_a::UInt8
#JuliaLang#215::Some{Nothing}
#JuliaLang#216::Union{Nothing, UInt8}
#JuliaLang#217::Union{Nothing, Some{UInt8}}
#JuliaLang#212::Some{Nothing}
#JuliaLang#213::Union{Nothing, Some{UInt8}}
#JuliaLang#214::Union{Nothing, UInt8}
digitRes::Union{Nothing, Some{UInt8}}
@_19::Union{Nothing, UInt8}
@_20::Union{Nothing, UInt8}
@_21::Nothing
@_22::Union{Nothing, UInt8}
@_23::Union{Nothing, UInt8}
@_24::Nothing
Body::Int64
1 ── (total = 0)
│ (may_a = Main.nothing)
│ (may_b = Main.nothing)
│ %4 = data::Vector{UInt8}
│ (@_3 = Base.iterate(%4))
│ %6 = @_3::Union{Nothing, Tuple{UInt8, Int64}}
│ %7 = (%6 === nothing)::Bool
│ %8 = Base.not_int(%7)::Bool
└─── goto mmtk#24 if not %8
2 ┄─ Core.NewvarNode(:(val@_7))
│ Core.NewvarNode(:(val@_8))
│ Core.NewvarNode(:(digit_b))
│ Core.NewvarNode(:(digit_a))
│ Core.NewvarNode(:(#JuliaLang#215))
│ Core.NewvarNode(:(#JuliaLang#216))
│ Core.NewvarNode(:(#JuliaLang#217))
│ Core.NewvarNode(:(#JuliaLang#212))
│ Core.NewvarNode(:(#JuliaLang#213))
│ %19 = @_3::Tuple{UInt8, Int64}
│ (c = Core.getfield(%19, 1))
│ %21 = Core.getfield(%19, 2)::Int64
│ %22 = c::UInt8
│ (digitRes = Main.someDigit(%22))
│ %24 = may_a::Union{Nothing, UInt8}
│ (#JuliaLang#214 = %24)
│ %26 = Base.:!::Core.Const(!)
│ %27 = #JuliaLang#214::Union{Nothing, UInt8}
│ %28 = Base.isnothing(%27)::Bool
│ %29 = (%26)(%28)::Bool
└─── goto mmtk#4 if not %29
3 ── %31 = #JuliaLang#214::UInt8
│ (@_19 = Base.something(%31))
└─── goto mmtk#11
4 ── %34 = digitRes::Union{Nothing, Some{UInt8}}
│ (#JuliaLang#213 = %34)
│ %36 = Base.:!::Core.Const(!)
│ %37 = #JuliaLang#213::Union{Nothing, Some{UInt8}}
│ %38 = Base.isnothing(%37)::Bool
│ %39 = (%36)(%38)::Bool
└─── goto mmtk#6 if not %39
5 ── %41 = #JuliaLang#213::Some{UInt8}
│ (@_20 = Base.something(%41))
└─── goto mmtk#10
6 ── %44 = Main.Some::Core.Const(Some)
│ %45 = Main.nothing::Core.Const(nothing)
│ (#JuliaLang#212 = (%44)(%45))
│ %47 = Base.:!::Core.Const(!)
│ %48 = #JuliaLang#212::Core.Const(Some(nothing))
│ %49 = Base.isnothing(%48)::Core.Const(false)
│ %50 = (%47)(%49)::Core.Const(true)
└─── goto mmtk#8 if not %50
7 ── %52 = #JuliaLang#212::Core.Const(Some(nothing))
│ (@_21 = Base.something(%52))
└─── goto mmtk#9
8 ── Core.Const(nothing)
│ Core.Const(:(val@_8 = Base.something(Base.nothing)))
│ Core.Const(nothing)
│ Core.Const(:(val@_8))
└─── Core.Const(:(@_21 = %58))
9 ┄─ %60 = @_21::Core.Const(nothing)
└─── (@_20 = %60)
10 ┄ %62 = @_20::Union{Nothing, UInt8}
└─── (@_19 = %62)
11 ┄ %64 = @_19::Union{Nothing, UInt8}
│ (may_a = %64)
│ %66 = digitRes::Union{Nothing, Some{UInt8}}
│ (#JuliaLang#217 = %66)
│ %68 = Base.:!::Core.Const(!)
│ %69 = #JuliaLang#217::Union{Nothing, Some{UInt8}}
│ %70 = Base.isnothing(%69)::Bool
│ %71 = (%68)(%70)::Bool
└─── goto mmtk#13 if not %71
12 ─ %73 = #JuliaLang#217::Some{UInt8}
│ (@_22 = Base.something(%73))
└─── goto mmtk#20
13 ─ %76 = may_b::Union{Nothing, UInt8}
│ (#JuliaLang#216 = %76)
│ %78 = Base.:!::Core.Const(!)
│ %79 = #JuliaLang#216::Union{Nothing, UInt8}
│ %80 = Base.isnothing(%79)::Bool
│ %81 = (%78)(%80)::Bool
└─── goto mmtk#15 if not %81
14 ─ %83 = #JuliaLang#216::UInt8
│ (@_23 = Base.something(%83))
└─── goto mmtk#19
15 ─ %86 = Main.Some::Core.Const(Some)
│ %87 = Main.nothing::Core.Const(nothing)
│ (#JuliaLang#215 = (%86)(%87))
│ %89 = Base.:!::Core.Const(!)
│ %90 = #JuliaLang#215::Core.Const(Some(nothing))
│ %91 = Base.isnothing(%90)::Core.Const(false)
│ %92 = (%89)(%91)::Core.Const(true)
└─── goto mmtk#17 if not %92
16 ─ %94 = #JuliaLang#215::Core.Const(Some(nothing))
│ (@_24 = Base.something(%94))
└─── goto mmtk#18
17 ─ Core.Const(nothing)
│ Core.Const(:(val@_7 = Base.something(Base.nothing)))
│ Core.Const(nothing)
│ Core.Const(:(val@_7))
└─── Core.Const(:(@_24 = %100))
18 ┄ %102 = @_24::Core.Const(nothing)
└─── (@_23 = %102)
19 ┄ %104 = @_23::Union{Nothing, UInt8}
└─── (@_22 = %104)
20 ┄ %106 = @_22::Union{Nothing, UInt8}
│ (may_b = %106)
│ %108 = Main.:(==)::Core.Const(==)
│ %109 = c::UInt8
│ %110 = Main.UInt8('\n')::Core.Const(0x0a)
│ %111 = (%108)(%109, %110)::Bool
└─── goto mmtk#22 if not %111
21 ─ %113 = may_a::Union{Nothing, UInt8}
│ (digit_a = Core.typeassert(%113, Main.UInt8))
│ %115 = may_b::Union{Nothing, UInt8}
│ (digit_b = Core.typeassert(%115, Main.UInt8))
│ %117 = Main.:+::Core.Const(+)
│ %118 = total::Int64
│ %119 = Main.:+::Core.Const(+)
│ %120 = Main.:*::Core.Const(*)
│ %121 = digit_a::UInt8
│ %122 = (%120)(%121, 0x0a)::UInt8
│ %123 = digit_b::UInt8
│ %124 = (%119)(%122, %123)::UInt8
│ (total = (%117)(%118, %124))
│ (may_a = Main.nothing)
└─── (may_b = Main.nothing)
22 ┄ (@_3 = Base.iterate(%4, %21))
│ %129 = @_3::Union{Nothing, Tuple{UInt8, Int64}}
│ %130 = (%129 === nothing)::Bool
│ %131 = Base.not_int(%130)::Bool
└─── goto mmtk#24 if not %131
23 ─ goto mmtk#2
24 ┄ %134 = total::Int64
└─── return %134
```
</details>
<details>
<summary>`@code_native debuginfo=:none` After </summary>
```julia
julia> @code_native debuginfo=:none part1(data)
.text
.file "part1"
.globl julia_part1_1203 # -- Begin function julia_part1_1203
.p2align 4, 0x90
.type julia_part1_1203,@function
julia_part1_1203: # @julia_part1_1203
; Function Signature: part1(Array{UInt8, 1})
# %bb.0: # %top
#DEBUG_VALUE: part1:data <- [DW_OP_deref] $rdi
push rbp
mov rbp, rsp
push r15
push r14
push r13
push r12
push rbx
sub rsp, 40
vxorps xmm0, xmm0, xmm0
#APP
mov rax, qword ptr fs:[0]
#NO_APP
lea rdx, [rbp - 64]
vmovaps xmmword ptr [rbp - 64], xmm0
mov qword ptr [rbp - 48], 0
mov rcx, qword ptr [rax - 8]
mov qword ptr [rbp - 64], 4
mov rax, qword ptr [rcx]
mov qword ptr [rbp - 72], rcx # 8-byte Spill
mov qword ptr [rbp - 56], rax
mov qword ptr [rcx], rdx
#DEBUG_VALUE: part1:data <- [DW_OP_deref] 0
mov r15, qword ptr [rdi + 16]
test r15, r15
je .LBB0_1
# %bb.2: # %L34
mov r14, qword ptr [rdi]
dec r15
mov r11b, 1
mov r13b, 1
# implicit-def: $r12b
# implicit-def: $r10b
xor eax, eax
jmp .LBB0_3
.p2align 4, 0x90
.LBB0_4: # in Loop: Header=BB0_3 Depth=1
xor r11d, r11d
mov ebx, edi
mov r10d, r8d
.LBB0_9: # %L114
# in Loop: Header=BB0_3 Depth=1
mov r12d, esi
test r15, r15
je .LBB0_12
.LBB0_10: # %guard_exit126
# in Loop: Header=BB0_3 Depth=1
inc r14
dec r15
mov r13d, ebx
.LBB0_3: # %L36
# =>This Inner Loop Header: Depth=1
movzx edx, byte ptr [r14]
test r13b, 1
movzx edi, r13b
mov ebx, 1
mov ecx, 0
cmove ebx, edi
cmovne edi, ecx
movzx ecx, r10b
lea esi, [rdx - 48]
lea r9d, [rdx - 58]
movzx r8d, sil
cmove r8d, ecx
cmp r9b, -11
ja .LBB0_4
# %bb.5: # %L89
# in Loop: Header=BB0_3 Depth=1
test r11b, 1
jne .LBB0_8
# %bb.6: # %L102
# in Loop: Header=BB0_3 Depth=1
cmp dl, 10
jne .LBB0_7
# %bb.13: # %L106
# in Loop: Header=BB0_3 Depth=1
test r13b, 1
jne .LBB0_14
# %bb.11: # %L114.thread
# in Loop: Header=BB0_3 Depth=1
add ecx, ecx
mov bl, 1
mov r11b, 1
lea ecx, [rcx + 4*rcx]
add cl, r12b
movzx ecx, cl
add rax, rcx
test r15, r15
jne .LBB0_10
jmp .LBB0_12
.p2align 4, 0x90
.LBB0_8: # %L102.thread
# in Loop: Header=BB0_3 Depth=1
mov r11b, 1
# implicit-def: $sil
cmp dl, 10
jne .LBB0_9
jmp .LBB0_15
.LBB0_7: # in Loop: Header=BB0_3 Depth=1
mov esi, r12d
jmp .LBB0_9
.LBB0_1:
xor eax, eax
.LBB0_12: # %L154
mov rcx, qword ptr [rbp - 56]
mov rdx, qword ptr [rbp - 72] # 8-byte Reload
mov qword ptr [rdx], rcx
add rsp, 40
pop rbx
pop r12
pop r13
pop r14
pop r15
pop rbp
ret
.LBB0_15: # %L106.thread
test r13b, 1
jne .LBB0_14
# %bb.16: # %post_box_union47
movabs rax, offset jl_nothing
movabs rcx, offset jl_small_typeof
movabs rdi, offset ".L_j_str_typeassert#1"
mov rdx, qword ptr [rax]
mov rsi, qword ptr [rcx + 336]
movabs rax, offset ijl_type_error
mov qword ptr [rbp - 48], rsi
call rax
.LBB0_14: # %post_box_union
movabs rax, offset jl_nothing
movabs rcx, offset jl_small_typeof
movabs rdi, offset ".L_j_str_typeassert#1"
mov rdx, qword ptr [rax]
mov rsi, qword ptr [rcx + 336]
movabs rax, offset ijl_type_error
mov qword ptr [rbp - 48], rsi
call rax
.Lfunc_end0:
.size julia_part1_1203, .Lfunc_end0-julia_part1_1203
# -- End function
.type ".L_j_str_typeassert#1",@object # @"_j_str_typeassert#1"
.section .rodata.str1.1,"aMS",@progbits,1
".L_j_str_typeassert#1":
.asciz "typeassert"
.size ".L_j_str_typeassert#1", 11
.section ".note.GNU-stack","",@progbits
```
</details>
Co-authored-by: Sukera <[email protected]>
udesou
pushed a commit
to udesou/julia
that referenced
this pull request
Oct 16, 2024
E.g. this allows `finalizer` inlining in the following case:
```julia
mutable struct ForeignBuffer{T}
const ptr::Ptr{T}
end
const foreign_buffer_finalized = Ref(false)
function foreign_alloc(::Type{T}, length) where T
ptr = Libc.malloc(sizeof(T) * length)
ptr = Base.unsafe_convert(Ptr{T}, ptr)
obj = ForeignBuffer{T}(ptr)
return finalizer(obj) do obj
Base.@assume_effects :notaskstate :nothrow
foreign_buffer_finalized[] = true
Libc.free(obj.ptr)
end
end
function f_EA_finalizer(N::Int)
workspace = foreign_alloc(Float64, N)
GC.@preserve workspace begin
(;ptr) = workspace
Base.@assume_effects :nothrow @noinline println(devnull, "ptr = ", ptr)
end
end
```
```julia
julia> @code_typed f_EA_finalizer(42)
CodeInfo(
1 ── %1 = Base.mul_int(8, N)::Int64
│ %2 = Core.lshr_int(%1, 63)::Int64
│ %3 = Core.trunc_int(Core.UInt8, %2)::UInt8
│ %4 = Core.eq_int(%3, 0x01)::Bool
└─── goto mmtk#3 if not %4
2 ── invoke Core.throw_inexacterror(:convert::Symbol, UInt64::Type, %1::Int64)::Union{}
└─── unreachable
3 ── goto mmtk#4
4 ── %9 = Core.bitcast(Core.UInt64, %1)::UInt64
└─── goto mmtk#5
5 ── goto mmtk#6
6 ── goto mmtk#7
7 ── goto mmtk#8
8 ── %14 = $(Expr(:foreigncall, :(:malloc), Ptr{Nothing}, svec(UInt64), 0, :(:ccall), :(%9), :(%9)))::Ptr{Nothing}
└─── goto mmtk#9
9 ── %16 = Base.bitcast(Ptr{Float64}, %14)::Ptr{Float64}
│ %17 = %new(ForeignBuffer{Float64}, %16)::ForeignBuffer{Float64}
└─── goto mmtk#10
10 ─ %19 = $(Expr(:gc_preserve_begin, :(%17)))
│ %20 = Base.getfield(%17, :ptr)::Ptr{Float64}
│ invoke Main.println(Main.devnull::Base.DevNull, "ptr = "::String, %20::Ptr{Float64})::Nothing
│ $(Expr(:gc_preserve_end, :(%19)))
│ %23 = Main.foreign_buffer_finalized::Base.RefValue{Bool}
│ Base.setfield!(%23, :x, true)::Bool
│ %25 = Base.getfield(%17, :ptr)::Ptr{Float64}
│ %26 = Base.bitcast(Ptr{Nothing}, %25)::Ptr{Nothing}
│ $(Expr(:foreigncall, :(:free), Nothing, svec(Ptr{Nothing}), 0, :(:ccall), :(%26), :(%25)))::Nothing
└─── return nothing
) => Nothing
```
However, this is still a WIP. Before merging, I want to improve EA's
precision a bit and at least fix the test case that is currently marked
as `broken`. I also need to check its impact on compiler performance.
Additionally, I believe this feature is not yet practical. In
particular, there is still significant room for improvement in the
following areas:
- EA's interprocedural capabilities: currently EA is performed ad-hoc
for limited frames because of latency reasons, which significantly
reduces its precision in the presence of interprocedural calls.
- Relaxing the `:nothrow` check for finalizer inlining: the current
algorithm requires `:nothrow`-ness on all paths from the allocation of
the mutable struct to its last use, which is not practical for
real-world cases. Even when `:nothrow` cannot be guaranteed, auxiliary
optimizations such as inserting a `finalize` call after the last use
might still be possible (JuliaLang#55990).
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This PR implements the write barrier fastpath for sticky immix in both the runtime write barrier and the codegen write barrier. There are also a few other changes: 1. pass collection type to MMTk's
handle_user_collection_request, 2. call MMTk injl_gc_notify_image_alloc.