gistfile1.txt

For the folllowing code:

var v = 5

@inline(never) func foo() {
    v += 10
}

class C<T> {
    
    let t: T
    
    @inline(never) init(t: T) {
        self.t = t
    }
}

let c = C(t: foo)
c.t()

The canonical SIL emitted for the main function in a -O build (xcrun swiftc -O -emit-sil main.swift | xcrun swift-demangle > main.silgen):

// main
sil @main : $@convention(c) (Int32, UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>) -> Int32 {
// %0                                             // user: %3
// %1                                             // user: %9
bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>):
  %2 = global_addr @static Swift.CommandLine._argc : Swift.Int32 : $*Int32, scope 1 // user: %3
  store %0 to %2 : $*Int32, scope 1               // id: %3
  %4 = global_addr @globalinit_33_FD9A49A256BEB6AF7C48013347ADC3BA_token4 : $*Builtin.Word, scope 1 // user: %5
  %5 = address_to_pointer %4 : $*Builtin.Word to $Builtin.RawPointer, scope 1 // user: %7
  // function_ref globalinit_33_FD9A49A256BEB6AF7C48013347ADC3BA_func4
  %6 = function_ref @globalinit_33_FD9A49A256BEB6AF7C48013347ADC3BA_func4 : $@convention(thin) () -> (), scope 1 // user: %7
  %7 = builtin "once"(%5 : $Builtin.RawPointer, %6 : $@convention(thin) () -> ()) : $(), scope 1
  %8 = global_addr @static Swift.CommandLine._unsafeArgv : Swift.UnsafeMutablePointer<Swift.UnsafeMutablePointer<Swift.Int8>?> : $*UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>, scope 1 // user: %9
  store %1 to %8 : $*UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>, scope 1 // id: %9

  // Allocate new global variable "v", and initialise it with the Int 5.
  alloc_global @main.v : Swift.Int, loc "main.swift":33:5, scope 1 // id: %10
  %11 = global_addr @main.v : Swift.Int : $*Int, loc "main.swift":33:5, scope 1 // user: %14
  %12 = integer_literal $Builtin.Int64, 5, loc "main.swift":33:9, scope 1 // user: %13
  %13 = struct $Int (%12 : $Builtin.Int64), loc "main.swift":33:9, scope 1 // user: %14
  store %13 to %11 : $*Int, loc "main.swift":33:9, scope 1 // id: %14

  // Allocate new global variable "c".
  alloc_global @main.c : main.C<() -> ()>, loc "main.swift":48:5, scope 1 // id: %15
  %16 = global_addr @main.c : main.C<() -> ()> : $*C<() -> ()>, loc "main.swift":48:5, scope 1 // user: %21
  // function_ref specialized thunk

  // Get a reference to the specialised thunk helper for the function foo().
  %17 = function_ref @function signature specialization <Arg[0] = [Constant Propagated Function : main.foo () -> ()]> of reabstraction thunk helper from @callee_owned () -> () to @callee_owned (@in ()) -> (@out ()) : $@convention(thin) (@in ()) -> @out (), loc "main.swift":48:14, scope 1 // user: %18

  // Convert the thunk helper from a thin to thick function.
  %18 = thin_to_thick_function %17 : $@convention(thin) (@in ()) -> @out () to $@callee_owned (@in ()) -> @out (), loc "main.swift":48:14, scope 1 // user: %20
  // function_ref specialized specialized C.__allocating_init(t : A) -> C<A>

  // Get C<() -> ()>'s specialised init.
  %19 = function_ref @function signature specialization <Arg[1] = Dead> of generic specialization <() -> ()> of main.C.__allocating_init (t : A) -> main.C<A> : $@convention(thin) (@owned @callee_owned (@in ()) -> @out ()) -> @owned C<() -> ()>, loc "main.swift":43:20, scope 4 // user: %20

  // Apply it with the specialised thunk helper, and store the result in the global variable "c".
  %20 = apply %19(%18) : $@convention(thin) (@owned @callee_owned (@in ()) -> @out ()) -> @owned C<() -> ()>, loc "main.swift":43:20, scope 4 // users: %21, %22
  store %20 to %16 : $*C<() -> ()>, loc "main.swift":48:17, scope 1 // id: %21

  // Call c.t()...
  %22 = ref_element_addr %20 : $C<() -> ()>, #C.t, loc "main.swift":49:3, scope 1 // user: %23
  %23 = load %22 : $*@callee_owned (@in ()) -> @out (), loc "main.swift":49:3, scope 1 // users: %26, %27
  %24 = alloc_stack $(), loc "main.swift":49:5, scope 1 // users: %29, %27
  %25 = alloc_stack $(), loc "main.swift":49:5, scope 1 // users: %28, %27
  strong_retain %23 : $@callee_owned (@in ()) -> @out (), scope 1 // id: %26
  %27 = apply %23(%25, %24) : $@callee_owned (@in ()) -> @out (), loc "main.swift":49:5, scope 1
  dealloc_stack %25 : $*(), loc "main.swift":49:5, scope 1 // id: %28
  dealloc_stack %24 : $*(), loc "main.swift":49:5, scope 1 // id: %29
  %30 = integer_literal $Builtin.Int32, 0, scope 1 // user: %31
  %31 = struct $Int32 (%30 : $Builtin.Int32), scope 1 // user: %32
  return %31 : $Int32, scope 1                    // id: %32
}