[swift-dev] High-level SIL Optimization: How do I get a FuncRef from the stdlib?

Sun Nov 27 13:11:40 CST 2016

+CC Slava.

He has been messing around with this area in the past bit since many of us have looked at this. He is the person you want.

Michael

> On Nov 25, 2016, at 8:42 PM, Ben Ng <me at benng.me> wrote:
> 
> Hi everyone,
> 
> I’ve made good progress with the information in this thread but I can’t figure out how to create the proper set of substitutions for the method that I’m calling.
> 
> The error I’m getting, as expected, is "SIL verification failed: callee of apply without substitutions must not be polymorphic: !fnTy->isPolymorphic()"
> 
> I was hoping that there would be a way to delay specialization of the function that I’m replacing so that I can simply reuse those substitutions, but it doesn’t seem like that’s possible.
> 
> At a high level I assumed that I’d simply be able to substitute a type like `Int` for `τ_0_0`, but it looks like I have to use a ProtocolConformanceRef, which I don’t understand.
> 
> I looked into iterating through `getLoweredFunctionType()->getGenericSignature()->getGenericParams()`, but I don’t see how I can turn the information there into ProtocolConformanceRef.
> 
> Thanks for the help as always,
> 
> Ben
> 
>> On Nov 16, 2016, at 10:47 PM, Ben Ng <me at benng.me> wrote:
>> 
>>> On Nov 16, 2016, at 7:11 PM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:
>>> 
>>> 
>>>> On Nov 16, 2016, at 2:58 PM, Ben Ng <me at benng.me> wrote:
>>>> 
>>>> Correct, that is what I am trying to do.
>>>> 
>>>>> On Nov 16, 2016, at 12:22 PM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:
>>>>> 
>>>>> // Really, by the time you look at this in array value prop
>>>>> // this call should have been inline and you would see a call
>>>>> // to:
>>>>> // a.append(contentsOf: [1])
>>>> 
>>>> I do not understand this comment; I thought that inlining of stdlib functions happened after high-level SIL optimizations are run. Is my understanding incorrect?
>>> 
>>> 
>>> Inlining of functions with @_semantics is delayed until after high-level SIL optimizations are run. Other functions are inlined.
>>> 
>>> https://github.com/apple/swift/blob/master/lib/SILOptimizer/PassManager/Passes.cpp#L221
>>> https://github.com/apple/swift/blob/master/lib/SILOptimizer/Transforms/PerformanceInliner.cpp#L722
>>> 
>>> 
>>> I recommend looking at the SIL function dump in ArrayElementValuePropagation of an example function after adding @semantics(“array.mutate_unknown”) to “append(contentsOf:)”.
>>> 
>>> 
>>> $ git diff HEAD~
>>> diff --git a/lib/SILOptimizer/Transforms/ArrayElementValuePropagation.cpp b/lib/SILOptimizer/Transforms/ArrayElementValuePropagation.cpp
>>> index 76328a6..cb976f7 100644
>>> --- a/lib/SILOptimizer/Transforms/ArrayElementValuePropagation.cpp
>>> +++ b/lib/SILOptimizer/Transforms/ArrayElementValuePropagation.cpp
>>> @@ -259,6 +259,8 @@ public:
>>> void run() override {
>>>   auto &Fn = *getFunction();
>>> 
>>> +    Fn.dump();
>>> +
>>>   bool Changed = false;
>>> 
>>>   // Propagate the elements an of array value to its users.
>>> diff --git a/stdlib/public/core/Arrays.swift.gyb b/stdlib/public/core/Arrays.swift.gyb
>>> index f00cc23..2acfd06 100644
>>> --- a/stdlib/public/core/Arrays.swift.gyb
>>> +++ b/stdlib/public/core/Arrays.swift.gyb
>>> @@ -1344,6 +1344,7 @@ extension ${Self} : RangeReplaceableCollection, _ArrayProtocol {
>>> /// - Parameter newElements: The elements to append to the array.
>>> ///
>>> /// - Complexity: O(*n*), where *n* is the length of the resulting array.
>>> +  @_semantics("array.mutate_unknown")
>>> public mutating func append<C : Collection>(contentsOf newElements: C)
>>>   where C.Iterator.Element == Element {
>>> 
>>> 
>>> # Rebuild the compiler and stdlib (without stdlib assertions).
>>> $ swift/utils/build-script -r  --assertions --no-swift-stdlib-assertions
>>> 
>>> 
>>> $ cat TestArray.swift 
>>> @inline(never)
>>> public func test() {
>>> var a = [1, 2, 3]
>>> a += [1]
>>> print(a)
>>> }
>>> 
>>> $ bin/swiftc -O 2>&1 | less
>>> ...
>>> sil shared [_semantics "array.mutate_unknown"] @_TTSg5Si_GSaSi_GSaSi_s10Collections___TFSa6appenduRd__s10CollectionxzWd__8Iterator7Element_rfT10contentsOfqd___T_ : $@convention(method) (@owned Array<I
>>> nt>, @inout Array<Int>) -> () {
>>> 
>>> …
>>> // testArray() -> ()
>>> sil [noinline] @_TF9TestArray9testArrayFT_T_ : $@convention(thin) () -> () {
>>> bb0:
>>> %0 = alloc_stack $Array<Int>, var, name "a", loc "TestArray.swift":3:7, scope 2 // users: %54, %32, %60, %23, %43
>>> %1 = integer_literal $Builtin.Word, 3, loc "TestArray.swift":3:12, scope 2 // user: %4
>>> %2 = integer_literal $Builtin.Int64, 3, scope 5 // user: %3
>>> %3 = struct $Int (%2 : $Builtin.Int64), scope 5 // users: %22, %7
>>> %4 = alloc_ref [tail_elems $Int * %1 : $Builtin.Word] $_ContiguousArrayStorage<Int>, scope 5 // user: %7
>>> %5 = metatype $@thin Array<Int>.Type, scope 5   // users: %25, %7
>>> // function_ref specialized static Array._adoptStorage(_ContiguousArrayStorage<A>, count : Int) -> ([A], UnsafeMutablePointer<A>)
>>> %6 = function_ref @_TTSg5Si___TZFSa13_adoptStoragefTGCs23_ContiguousArrayStoragex_5countSi_TGSax_GSpx__ : $@convention(method) (@owned _ContiguousArrayStorage<Int>, Int, @thin Array<Int>.Type) -> (@
>>> owned Array<Int>, UnsafeMutablePointer<Int>), scope 5 // users: %25, %7
>>> %7 = apply %6(%4, %3, %5) : $@convention(method) (@owned _ContiguousArrayStorage<Int>, Int, @thin Array<Int>.Type) -> (@owned Array<Int>, UnsafeMutablePointer<Int>), scope 5 // users: %9, %8
>>> %8 = tuple_extract %7 : $(Array<Int>, UnsafeMutablePointer<Int>), 0, scope 5 // user: %23
>>> %9 = tuple_extract %7 : $(Array<Int>, UnsafeMutablePointer<Int>), 1, scope 5 // user: %10
>>> %10 = struct_extract %9 : $UnsafeMutablePointer<Int>, #UnsafeMutablePointer._rawValue, scope 5 // user: %11
>>> %11 = pointer_to_address %10 : $Builtin.RawPointer to [strict] $*Int, loc "TestArray.swift":3:12, scope 2 // users: %14, %21, %16
>>> %12 = integer_literal $Builtin.Int64, 1, loc "TestArray.swift":3:12, scope 2 // user: %13
>>> %13 = struct $Int (%12 : $Builtin.Int64), loc "TestArray.swift":3:12, scope 2 // users: %37, %30, %25, %14
>>> store %13 to %11 : $*Int, loc "TestArray.swift":3:12, scope 2 // id: %14
>>> %15 = integer_literal $Builtin.Word, 1, loc "TestArray.swift":3:15, scope 2 // users: %34, %24, %16
>>> %16 = index_addr %11 : $*Int, %15 : $Builtin.Word, loc "TestArray.swift":3:15, scope 2 // user: %19
>>> %17 = integer_literal $Builtin.Int64, 2, loc "TestArray.swift":3:15, scope 2 // user: %18
>>> %18 = struct $Int (%17 : $Builtin.Int64), loc "TestArray.swift":3:15, scope 2 // user: %19
>>> store %18 to %16 : $*Int, loc "TestArray.swift":3:15, scope 2 // id: %19
>>> %20 = integer_literal $Builtin.Word, 2, loc "TestArray.swift":3:18, scope 2 // user: %21
>>> %21 = index_addr %11 : $*Int, %20 : $Builtin.Word, loc "TestArray.swift":3:18, scope 2 // user: %22
>>> store %3 to %21 : $*Int, loc "TestArray.swift":3:18, scope 2 // id: %22
>>> store %8 to %0 : $*Array<Int>, loc "TestArray.swift":3:18, scope 2 // id: %23
>>> %24 = alloc_ref [tail_elems $Int * %15 : $Builtin.Word] $_ContiguousArrayStorage<Int>, scope 7 // user: %25
>>> %25 = apply %6(%24, %13, %5) : $@convention(method) (@owned _ContiguousArrayStorage<Int>, Int, @thin Array<Int>.Type) -> (@owned Array<Int>, UnsafeMutablePointer<Int>), scope 7 // users: %27, %26
>>> %26 = tuple_extract %25 : $(Array<Int>, UnsafeMutablePointer<Int>), 0, scope 7 // user: %32
>>> %27 = tuple_extract %25 : $(Array<Int>, UnsafeMutablePointer<Int>), 1, scope 7 // user: %28
>>> %28 = struct_extract %27 : $UnsafeMutablePointer<Int>, #UnsafeMutablePointer._rawValue, scope 7 // user: %29
>>> %29 = pointer_to_address %28 : $Builtin.RawPointer to [strict] $*Int, loc "TestArray.swift":4:9, scope 2 // user: %30
>>> store %13 to %29 : $*Int, loc "TestArray.swift":4:9, scope 2 // id: %30
>>> // function_ref specialized Array.append<A where ...> (contentsOf : A1) -> ()
>>> %31 = function_ref @_TTSg5Si_GSaSi_GSaSi_s10Collections___TFSa6appenduRd__s10CollectionxzWd__8Iterator7Element_rfT10contentsOfqd___T_ : $@convention(method) (@owned Array<Int>, @inout Array<Int>) -> (), scope 10 // user: %32
>>> %32 = apply %31(%26, %0) : $@convention(method) (@owned Array<Int>, @inout Array<Int>) -> (), scope 10
>> 
>> Ah, I do remember seeing something about how the semantic attribute stops some functions from being inlined early. Thanks for saving me a bunch of head-scratching!
>> 
>> 
> 