#adjoint expression crasher (https://bugs.swift.org/browse/SR-8087)

README.md

The red - lines are produced by direct references to Tensor.dfoo, which doesn't crash.

The green + lines are produced by #adjoint(Tensor.foo), which does crashes.

adjoint_expr_crasher.diff

diff --git a/a1.sil b/a2.sil
index 30ad601..7d92e01 100644
--- a/a1.sil
+++ b/a2.sil
@@ -1,128 +1,142 @@
 sil_stage raw

 import Builtin
 import Swift
 import SwiftShims

 import TensorFlow

 extension Tensor where Scalar : Numeric, Scalar : AccelerableByTensorFlow {
   @differentiable(reverse, adjoint: dfoo)
   static func foo(_ x: Tensor<Scalar>) -> Tensor<Scalar>
   static func dfoo(_ x: Tensor<Scalar>, originalValue: Tensor<Scalar>, seed: Tensor<Scalar>) -> Tensor<Scalar>
 }

 let x: Tensor<Float>

 // x
 sil_global hidden [let] @$S7crasher1x10TensorFlow0B0VySfGvp : $Tensor<Float>

 // main
 sil @main : $@convention(c) (Int32, UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>) -> Int32 {
 bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>):
   alloc_global @$S7crasher1x10TensorFlow0B0VySfGvp // id: %2
-  %3 = global_addr @$S7crasher1x10TensorFlow0B0VySfGvp : $*Tensor<Float> // users: %34, %33, %32, %29, %28, %27, %14
+  %3 = global_addr @$S7crasher1x10TensorFlow0B0VySfGvp : $*Tensor<Float> // users: %37, %36, %35, %31, %30, %29, %14
   %4 = metatype $@thin Tensor<Float>.Type         // user: %12
   %5 = metatype $@thin Float.Type                 // user: %8
   %6 = integer_literal $Builtin.Int2048, 1        // user: %8
   // function_ref Float.init(_builtinIntegerLiteral:)
   %7 = function_ref @$SSf22_builtinIntegerLiteralSfBi2048__tcfC : $@convention(method) (Builtin.Int2048, @thin Float.Type) -> Float // user: %8
   %8 = apply %7(%6, %5) : $@convention(method) (Builtin.Int2048, @thin Float.Type) -> Float // user: %10
   %9 = alloc_stack $Float                         // users: %13, %12, %10
   store %8 to [trivial] %9 : $*Float              // id: %10
   // function_ref Tensor.init(_:)
   %11 = function_ref @$S10TensorFlow0A0VyACyxGxcfC : $@convention(method) <τ_0_0 where τ_0_0 : AccelerableByTensorFlow> (@in τ_0_0, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0> // user: %12
   %12 = apply %11<Float>(%9, %4) : $@convention(method) <τ_0_0 where τ_0_0 : AccelerableByTensorFlow> (@in τ_0_0, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0> // user: %14
   dealloc_stack %9 : $*Float                      // id: %13
   store %12 to [init] %3 : $*Tensor<Float>        // id: %14
   %15 = integer_literal $Builtin.Word, 1          // user: %17
   // function_ref _allocateUninitializedArray<A>(_:)
   %16 = function_ref @$Ss27_allocateUninitializedArrayySayxG_BptBwlF : $@convention(thin) <τ_0_0> (Builtin.Word) -> (@owned Array<τ_0_0>, Builtin.RawPointer) // user: %17
   %17 = apply %16<Any>(%15) : $@convention(thin) <τ_0_0> (Builtin.Word) -> (@owned Array<τ_0_0>, Builtin.RawPointer) // users: %23, %22, %18
   %18 = begin_borrow %17 : $(Array<Any>, Builtin.RawPointer) // users: %22, %21, %19
   %19 = tuple_extract %18 : $(Array<Any>, Builtin.RawPointer), 0 // user: %20
-  %20 = copy_value %19 : $Array<Any>              // users: %44, %41
+  %20 = copy_value %19 : $Array<Any>              // users: %48, %44
   %21 = tuple_extract %18 : $(Array<Any>, Builtin.RawPointer), 1 // user: %24
   end_borrow %18 from %17 : $(Array<Any>, Builtin.RawPointer), $(Array<Any>, Builtin.RawPointer) // id: %22
   destroy_value %17 : $(Array<Any>, Builtin.RawPointer) // id: %23
   %24 = pointer_to_address %21 : $Builtin.RawPointer to [strict] $*Any // user: %25
-  %25 = init_existential_addr %24 : $*Any, $Tensor<Float> // user: %35
-  %26 = metatype $@thin Tensor<Float>.Type        // user: %31
-  %27 = load_borrow %3 : $*Tensor<Float>          // users: %34, %31
-  %28 = load_borrow %3 : $*Tensor<Float>          // users: %33, %31
-  %29 = load_borrow %3 : $*Tensor<Float>          // users: %32, %31
-  // function_ref static Tensor<>.dfoo(_:originalValue:seed:)
-  %30 = function_ref @$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZ : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0> // user: %31
-  %31 = apply %30<Float>(%27, %28, %29, %26) : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0> // user: %35
-  end_borrow %29 from %3 : $Tensor<Float>, $*Tensor<Float> // id: %32
-  end_borrow %28 from %3 : $Tensor<Float>, $*Tensor<Float> // id: %33
-  end_borrow %27 from %3 : $Tensor<Float>, $*Tensor<Float> // id: %34
-  store %31 to [init] %25 : $*Tensor<Float>       // id: %35
+  %25 = init_existential_addr %24 : $*Any, $Tensor<Float> // user: %38
+  // function_ref curry thunk of static Tensor<>.dfoo(_:originalValue:seed:)
+  %26 = function_ref @$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZTc : $@convention(thin) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow> (@thin Tensor<τ_0_0>.Type) -> @owned @callee_guaranteed (@guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>) -> @owned Tensor<τ_0_0> // user: %28
+  %27 = metatype $@thin Tensor<Float>.Type        // user: %28
+  %28 = apply %26<Float>(%27) : $@convention(thin) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow> (@thin Tensor<τ_0_0>.Type) -> @owned @callee_guaranteed (@guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>) -> @owned Tensor<τ_0_0> // users: %47, %34, %32
+  %29 = load_borrow %3 : $*Tensor<Float>          // users: %37, %33
+  %30 = load_borrow %3 : $*Tensor<Float>          // users: %36, %33
+  %31 = load_borrow %3 : $*Tensor<Float>          // users: %35, %33
+  %32 = begin_borrow %28 : $@callee_guaranteed (@guaranteed Tensor<Float>, @guaranteed Tensor<Float>, @guaranteed Tensor<Float>) -> @owned Tensor<Float> // users: %34, %33
+  %33 = apply %32(%29, %30, %31) : $@callee_guaranteed (@guaranteed Tensor<Float>, @guaranteed Tensor<Float>, @guaranteed Tensor<Float>) -> @owned Tensor<Float> // user: %38
+  end_borrow %32 from %28 : $@callee_guaranteed (@guaranteed Tensor<Float>, @guaranteed Tensor<Float>, @guaranteed Tensor<Float>) -> @owned Tensor<Float>, $@callee_guaranteed (@guaranteed Tensor<Float>, @guaranteed Tensor<Float>, @guaranteed Tensor<Float>) -> @owned Tensor<Float> // id: %34
+  end_borrow %31 from %3 : $Tensor<Float>, $*Tensor<Float> // id: %35
+  end_borrow %30 from %3 : $Tensor<Float>, $*Tensor<Float> // id: %36
+  end_borrow %29 from %3 : $Tensor<Float>, $*Tensor<Float> // id: %37
+  store %33 to [init] %25 : $*Tensor<Float>       // id: %38
   // function_ref default argument 1 of print(_:separator:terminator:)
-  %36 = function_ref @$Ss5print_9separator10terminatoryypd_S2StFfA0_ : $@convention(thin) () -> @owned String // user: %37
-  %37 = apply %36() : $@convention(thin) () -> @owned String // users: %43, %41
+  %39 = function_ref @$Ss5print_9separator10terminatoryypd_S2StFfA0_ : $@convention(thin) () -> @owned String // user: %40
+  %40 = apply %39() : $@convention(thin) () -> @owned String // users: %46, %44
   // function_ref default argument 2 of print(_:separator:terminator:)
-  %38 = function_ref @$Ss5print_9separator10terminatoryypd_S2StFfA1_ : $@convention(thin) () -> @owned String // user: %39
-  %39 = apply %38() : $@convention(thin) () -> @owned String // users: %42, %41
+  %41 = function_ref @$Ss5print_9separator10terminatoryypd_S2StFfA1_ : $@convention(thin) () -> @owned String // user: %42
+  %42 = apply %41() : $@convention(thin) () -> @owned String // users: %45, %44
   // function_ref print(_:separator:terminator:)
-  %40 = function_ref @$Ss5print_9separator10terminatoryypd_S2StF : $@convention(thin) (@guaranteed Array<Any>, @guaranteed String, @guaranteed String) -> () // user: %41
-  %41 = apply %40(%20, %37, %39) : $@convention(thin) (@guaranteed Array<Any>, @guaranteed String, @guaranteed String) -> ()
-  destroy_value %39 : $String                     // id: %42
-  destroy_value %37 : $String                     // id: %43
-  destroy_value %20 : $Array<Any>                 // id: %44
-  %45 = integer_literal $Builtin.Int32, 0         // user: %46
-  %46 = struct $Int32 (%45 : $Builtin.Int32)      // user: %47
-  return %46 : $Int32                             // id: %47
+  %43 = function_ref @$Ss5print_9separator10terminatoryypd_S2StF : $@convention(thin) (@guaranteed Array<Any>, @guaranteed String, @guaranteed String) -> () // user: %44
+  %44 = apply %43(%20, %40, %42) : $@convention(thin) (@guaranteed Array<Any>, @guaranteed String, @guaranteed String) -> ()
+  destroy_value %42 : $String                     // id: %45
+  destroy_value %40 : $String                     // id: %46
+  destroy_value %28 : $@callee_guaranteed (@guaranteed Tensor<Float>, @guaranteed Tensor<Float>, @guaranteed Tensor<Float>) -> @owned Tensor<Float> // id: %47
+  destroy_value %20 : $Array<Any>                 // id: %48
+  %49 = integer_literal $Builtin.Int32, 0         // user: %50
+  %50 = struct $Int32 (%49 : $Builtin.Int32)      // user: %51
+  return %50 : $Int32                             // id: %51
 } // end sil function 'main'

 // static Tensor<>.foo(_:)
 sil hidden [reverse_differentiable source 0 wrt 0 primal @$S10TensorFlow0A0V7crashers7NumericRzrlE3fooyACyxGAGFZ adjoint @$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZ] @$S10TensorFlow0A0V7crashers7NumericRzrlE3fooyACyxGAGFZ : $@convention(method) <Scalar where Scalar : Numeric, Scalar : AccelerableByTensorFlow> (@guaranteed Tensor<Scalar>, @thin Tensor<Scalar>.Type) -> @owned Tensor<Scalar> {
 // %0                                             // users: %4, %2
 // %1                                             // user: %3
 bb0(%0 : $Tensor<Scalar>, %1 : $@thin Tensor<Scalar>.Type):
   debug_value %0 : $Tensor<Scalar>, let, name "x", argno 1 // id: %2
   debug_value %1 : $@thin Tensor<Scalar>.Type, let, name "self", argno 2 // id: %3
   %4 = copy_value %0 : $Tensor<Scalar>            // user: %5
   return %4 : $Tensor<Scalar>                     // id: %5
 } // end sil function '$S10TensorFlow0A0V7crashers7NumericRzrlE3fooyACyxGAGFZ'

 // static Tensor<>.dfoo(_:originalValue:seed:)
 sil hidden @$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZ : $@convention(method) <Scalar where Scalar : Numeric, Scalar : AccelerableByTensorFlow> (@guaranteed Tensor<Scalar>, @guaranteed Tensor<Scalar>, @guaranteed Tensor<Scalar>, @thin Tensor<Scalar>.Type) -> @owned Tensor<Scalar> {
 // %0                                             // users: %9, %4
 // %1                                             // user: %5
 // %2                                             // users: %9, %6
 // %3                                             // user: %7
 bb0(%0 : $Tensor<Scalar>, %1 : $Tensor<Scalar>, %2 : $Tensor<Scalar>, %3 : $@thin Tensor<Scalar>.Type):
   debug_value %0 : $Tensor<Scalar>, let, name "x", argno 1 // id: %4
   debug_value %1 : $Tensor<Scalar>, let, name "originalValue", argno 2 // id: %5
   debug_value %2 : $Tensor<Scalar>, let, name "seed", argno 3 // id: %6
   debug_value %3 : $@thin Tensor<Scalar>.Type, let, name "self", argno 4 // id: %7
   // function_ref Tensor<>.unbroadcast<A>(like:)
   %8 = function_ref @$S10TensorFlow0A0VAAs7NumericRzrlE11unbroadcast4likeACyxGACyqd__G_tAA013AccelerableByaB0Rd__lF : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow><τ_1_0 where τ_1_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_1_0>, @guaranteed Tensor<τ_0_0>) -> @owned Tensor<τ_0_0> // user: %9
   %9 = apply %8<Scalar, Scalar>(%0, %2) : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow><τ_1_0 where τ_1_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_1_0>, @guaranteed Tensor<τ_0_0>) -> @owned Tensor<τ_0_0> // user: %10
   return %9 : $Tensor<Scalar>                     // id: %10
 } // end sil function '$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZ'

 // Tensor<>.unbroadcast<A>(like:)
 sil [serialized] [always_inline] @$S10TensorFlow0A0VAAs7NumericRzrlE11unbroadcast4likeACyxGACyqd__G_tAA013AccelerableByaB0Rd__lF : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow><τ_1_0 where τ_1_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_1_0>, @guaranteed Tensor<τ_0_0>) -> @owned Tensor<τ_0_0>

 // Float.init(_builtinIntegerLiteral:)
 sil [transparent] [serialized] @$SSf22_builtinIntegerLiteralSfBi2048__tcfC : $@convention(method) (Builtin.Int2048, @thin Float.Type) -> Float

 // Tensor.init(_:)
 sil [serialized] [always_inline] @$S10TensorFlow0A0VyACyxGxcfC : $@convention(method) <τ_0_0 where τ_0_0 : AccelerableByTensorFlow> (@in τ_0_0, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0>

 // _allocateUninitializedArray<A>(_:)
 sil [serialized] [always_inline] @$Ss27_allocateUninitializedArrayySayxG_BptBwlF : $@convention(thin) <τ_0_0> (Builtin.Word) -> (@owned Array<τ_0_0>, Builtin.RawPointer)

+// curry thunk of static Tensor<>.dfoo(_:originalValue:seed:)
+sil shared [thunk] @$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZTc : $@convention(thin) <Scalar where Scalar : Numeric, Scalar : AccelerableByTensorFlow> (@thin Tensor<Scalar>.Type) -> @owned @callee_guaranteed (@guaranteed Tensor<Scalar>, @guaranteed Tensor<Scalar>, @guaranteed Tensor<Scalar>) -> @owned Tensor<Scalar> {
+// %0                                             // user: %2
+bb0(%0 : $@thin Tensor<Scalar>.Type):
+  // function_ref static Tensor<>.dfoo(_:originalValue:seed:)
+  %1 = function_ref @$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZ : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0> // user: %2
+  %2 = partial_apply [callee_guaranteed] %1<Scalar>(%0) : $@convention(method) <τ_0_0 where τ_0_0 : Numeric, τ_0_0 : AccelerableByTensorFlow> (@guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @guaranteed Tensor<τ_0_0>, @thin Tensor<τ_0_0>.Type) -> @owned Tensor<τ_0_0> // user: %3
+  return %2 : $@callee_guaranteed (@guaranteed Tensor<Scalar>, @guaranteed Tensor<Scalar>, @guaranteed Tensor<Scalar>) -> @owned Tensor<Scalar> // id: %3
+} // end sil function '$S10TensorFlow0A0V7crashers7NumericRzrlE4dfoo_13originalValue4seedACyxGAI_A2ItFZTc'
+
 // default argument 1 of print(_:separator:terminator:)
 sil [noinline] @$Ss5print_9separator10terminatoryypd_S2StFfA0_ : $@convention(thin) () -> @owned String

 // default argument 2 of print(_:separator:terminator:)
 sil [noinline] @$Ss5print_9separator10terminatoryypd_S2StFfA1_ : $@convention(thin) () -> @owned String

 // print(_:separator:terminator:)
 sil [noinline] @$Ss5print_9separator10terminatoryypd_S2StF : $@convention(thin) (@guaranteed Array<Any>, @guaranteed String, @guaranteed String) -> ()

crasher.swift

import TensorFlow

extension Tensor where Scalar : Numeric {
  @differentiable(reverse, adjoint: dfoo)
  static func foo(_ x: Tensor) -> Tensor {
    return x
  }

  static func dfoo(
    _ x: Tensor, originalValue: Tensor, seed: Tensor
  ) -> Tensor {
    return seed.unbroadcast(like: x)
  }
}


let x = Tensor<Float>(1)

// Line 1: This works.
// print(Tensor<Float>.dfoo(x, originalValue: x, seed: x))

// Line 2: This crashes when uncommented.
print(#adjoint(Tensor<Float>.foo)(x, originalValue: x, seed: x))