Compiler: add Task call, invoke, and fetch optimizations and operations #59221

vtjnash · 2025-08-06T15:31:40Z

This commit implements a Task optimizations by adding a invoked field to the Task definition, which optionally causes it to do an invoke call internally instead of a regular call.

Key changes:

Add invoked field to Task structure, supporting Type, Method, MethodInstance, and CodeInstance, just like invoke
Implement _task builtin function to construct Task
Create PartialTask lattice element for precise task result and error type tracking
Unify several CallInfo types into IndirectCallInfo
Optimized calls to _task constructor to inject CodeInstance. Calling fully_covers isn't necessary, as the runtime will check that.

In the future we can consider making this field user-inaccessible (like scope) and then be able to optimize based on the type returned from fetch.

Also added documentation to base/docs/basedocs.jl on how to easily add more Builtin functions, following this as an example.

🤖 Generated with help from Claude Code

This commit implements a Task optimizations by adding a `invoked` field to the Task definition, which optionally causes it to do an `invoke` call internally instead of a regular `call`. Key changes: - Add `invoked` field to Task structure, supporting Type, Method, MethodInstance, and CodeInstance, just like invoke - Implement `_task` builtin function to construct Task - Create PartialTask lattice element for precise task result and error type tracking - Unify several CallInfo types into IndirectCallInfo - Optimized calls to `_task` constructor to inject CodeInstance. Calling `fully_covers` isn't necessary, as the runtime will check that. In the future we can make this field user-inaccessible (like scope) and then be able to optimize based on the type returned from `fetch`. Also added documentation to base/docs/basedocs.jl on how to easily add more Builtin functions, following this as an example. 🤖 Generated with help from [Claude Code](https://claude.ai/code)

JeffBezanson · 2025-08-06T18:13:19Z

Compiler/src/stmtinfo.jl

+ - `modifyglobal!(mod, var, op, x, order)` where `op(getval(), x)` is called
+ - `memoryrefmodify!(memref, op, x, order, boundscheck)` where `op(getval(), x)` is called
+ - `Intrinsics.atomic_pointermodify(ptr, op, x, order)` where `op(getval(), x)` is called
+ - `Core._task(f, size)` where `f()` will be called when the task runs


Aren't task and finalizer different from the modify functions in that the modify functions eagerly call the argument at the call site, while task and finalizer are deferred? I thought that was important.

JeffBezanson · 2025-08-06T19:24:02Z

stdlib/Serialization/src/Serialization.jl

@@ -498,6 +498,10 @@ function serialize(s::AbstractSerializer, t::Task)
    if istaskstarted(t) && !istaskdone(t)
        error("cannot serialize a running Task")
    end
+    if isdefined(t, :invoked)
+        error("cannot serialize a Task constructed with invoke info")


I'm not sure this is helpful, since if you hit this you can't really control it. We could just skip this field and hope it works out.

JeffBezanson · 2025-08-06T19:25:42Z

base/task.jl

@@ -2,7 +2,11 @@

 ## basic task functions and TLS

-Core.Task(@nospecialize(f), reserved_stack::Int=0) = Core._Task(f, reserved_stack, ThreadSynchronizer())
+Core.Task(@nospecialize(f), reserved_stack::Int=0) = begin


Suggested change

Core.Task(@nospecialize(f), reserved_stack::Int=0) = begin

function Core.Task(@nospecialize(f), reserved_stack::Int=0)

JeffBezanson · 2025-08-06T19:27:36Z

src/builtins.c

@@ -2160,6 +2160,18 @@ JL_CALLABLE(jl_f__svec_ref)
    return jl_svecref(s, idx-1);
 }

+JL_CALLABLE(jl_f__task)


I wonder how much overhead this has. Might need codegen support.

JeffBezanson · 2025-08-06T19:28:02Z

Any benchmarks?

aviatesk · 2025-08-06T19:26:36Z

Compiler/src/abstractinterpretation.jl

+    end
+    # Check that size argument is an Int
+    size_arg = argtypes[3]
+    if !(widenconst(size_arg) ⊑ Int)


Suggested change

if !(widenconst(size_arg) ⊑ Int)

if !hasintersect(widenconst(size_arg), Int)

aviatesk · 2025-08-06T19:26:53Z

Compiler/src/abstractinterpretation.jl

+    if la < 3 || la > 4
+        return Future(CallMeta(Bottom, Any, EFFECTS_THROWS, NoCallInfo()))
+    end
+    # Check that size argument is an Int


Suggested change

# Check that size argument is an Int

aviatesk · 2025-08-06T19:32:15Z

Compiler/src/abstractinterpretation.jl

+    # Check argument count: _task(func, size) or _task(func, size, ci)
+    if la < 3 || la > 4
+        return Future(CallMeta(Bottom, Any, EFFECTS_THROWS, NoCallInfo()))
+    end


Suggested change

# Check argument count: _task(func, size) or _task(func, size, ci)

if la < 3 || la > 4

return Future(CallMeta(Bottom, Any, EFFECTS_THROWS, NoCallInfo()))

end

if !isempty(argtypes) && !isvarargtype(argtypes[end])

if !(3 <= la <= 4)

return Future(CallMeta(Bottom, Any, EFFECTS_THROWS, NoCallInfo()))

end

elseif isempty(argtypes) || la > 5

return Future(CallMeta(Bottom, Any, EFFECTS_THROWS, NoCallInfo()))

end

aviatesk · 2025-08-06T19:43:19Z

Any benchmarks?

I was unable to confirm optimization results even in the simplest case on my end unfortunately.
Perhaps task construction/scheduling is becoming the bottleneck?

julia> func2(i) = fetch(Threads.@spawn sin(i));

julia> using BenchmarkTools

julia> @benchmark func2(42)

master:

BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (min … max):  709.000 ns …  34.583 μs  ┊ GC (min … max): 0.00% … 0.00%
 Time  (median):      12.667 μs               ┊ GC (median):    0.00%
 Time  (mean ± σ):    12.857 μs ± 976.688 ns  ┊ GC (mean ± σ):  0.00% ± 0.00%

                                            ▁▃▅▅█▇▄▄▅▄▃▂▁▁      ▂
  ▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▄████████████████▇▆▇ █
  709 ns        Histogram: log(frequency) by time       16.2 μs <

 Memory estimate: 352 bytes, allocs estimate: 6.

this PR:

BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (min … max):  11.333 μs …  29.542 μs  ┊ GC (min … max): 0.00% … 0.00%
 Time  (median):     12.708 μs               ┊ GC (median):    0.00%
 Time  (mean ± σ):   12.602 μs ± 587.109 ns  ┊ GC (mean ± σ):  0.00% ± 0.00%

  ▄▆▃         ▁   ▁▄▅▆▅▄▃▄▇▇██▆▆▅▂▁▁▂ ▁▁▁   ▁                  ▃
  ███▇▇▆▆▇█▇▇▇█▇▇████████████████████████▇▇▇██▇▇▇█▆▅▆█▆▆▆▇▆▄▆▅ █
  11.3 μs       Histogram: log(frequency) by time      14.4 μs <

 Memory estimate: 352 bytes, allocs estimate: 6.

vtjnash · 2025-08-06T23:35:02Z

It was entirely process_events and scheduling issues for me, which are separately addressable. The main point is inference and trim, not performance at this time.

vtjnash requested a review from aviatesk August 6, 2025 15:31

JeffBezanson reviewed Aug 6, 2025

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Compiler: add Task call, invoke, and fetch optimizations and operations #59221

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	Core.Task(@nospecialize(f), reserved_stack::Int=0) = begin
	function Core.Task(@nospecialize(f), reserved_stack::Int=0)

	if !(widenconst(size_arg) ⊑ Int)
	if !hasintersect(widenconst(size_arg), Int)

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Compiler: add Task call, invoke, and fetch optimizations and operations #59221

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