[SIL] Fix alloc_stack [dynamic_lifetime] attribute cloning.

Make `SILCloner:visitAllocStack` correctly propagate the `[dynamic_lifetime]`
attribute.

Resolves SR-12886: differentiation transform error related to the `VJPEmitter`
subclass of `SILCloner`.

Author: dan-zheng

include/swift/SIL/SILCloner.h

@@ -802,9 +802,9 @@ SILCloner<ImplClass>::visitAllocStackInst(AllocStackInst *Inst) {
     Loc = MandatoryInlinedLocation::getAutoGeneratedLocation();
     VarInfo = None;
   }
-  recordClonedInstruction(Inst,
-                          getBuilder().createAllocStack(
-                              Loc, getOpType(Inst->getElementType()), VarInfo));
+  recordClonedInstruction(Inst, getBuilder().createAllocStack(
+                                    Loc, getOpType(Inst->getElementType()),
+                                    VarInfo, Inst->hasDynamicLifetime()));
 }
 
 template<typename ImplClass>

test/AutoDiff/compiler_crashers_fixed/sr12886-clone-alloc-stack-dynamic-lifetime.swift

@@ -0,0 +1,42 @@
+// RUN: %target-build-swift %s
+// RUN: %target-swift-frontend -emit-sil %s | %FileCheck %s
+
+// SR-12493: SIL memory lifetime verification error due to
+// `SILCloner::visitAllocStack` not copying the `[dynamic_lifetime]` attribute.
+
+import _Differentiation
+
+enum Enum {
+  case a
+}
+
+struct Tensor<T>: Differentiable {
+  @noDerivative var x: T
+  @noDerivative var optional: Int?
+
+  init(_ x: T, _ e: Enum) {
+    self.x = x
+    switch e {
+      case .a: optional = 1
+    }
+  }
+
+  // Definite initialization triggers for this initializer.
+  @differentiable
+  init(_ x: T, _ other: Self) {
+    self = Self(x, Enum.a)
+  }
+}
+
+// Check that `allock_stack [dynamic_lifetime]` attribute is correctly cloned.
+
+// CHECK-LABEL: sil hidden @$s4main6TensorVyACyxGx_ADtcfC : $@convention(method) <T> (@in T, @in Tensor<T>, @thin Tensor<T>.Type) -> @out Tensor<T> {
+// CHECK: [[SELF_ALLOC:%.*]] = alloc_stack [dynamic_lifetime] $Tensor<T>, var, name "self"
+
+// CHECK-LABEL: sil hidden @AD__$s4main6TensorVyACyxGx_ADtcfC__vjp_src_0_wrt_1_l : $@convention(method) <τ_0_0> (@in τ_0_0, @in Tensor<τ_0_0>, @thin Tensor<τ_0_0>.Type) -> (@out Tensor<τ_0_0>, @owned @callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <Tensor<τ_0_0>.TangentVector, Tensor<τ_0_0>.TangentVector>) {
+// CHECK: [[SELF_ALLOC:%.*]] = alloc_stack [dynamic_lifetime] $Tensor<τ_0_0>, var, name "self"
+
+// Original error:
+// SIL memory lifetime failure in @AD__$s5crash6TensorVyACyxGx_ADtcfC__vjp_src_0_wrt_1_l: memory is not initialized, but should
+// memory location:   %29 = struct_element_addr %5 : $*Tensor<τ_0_0>, #Tensor.x // user: %30
+// at instruction:   destroy_addr %29 : $*τ_0_0                     // id: %30