[GenPack] Cast dynamic alloca to appropriate type.

If it's allocated in an async function or a coroutine, the element type
is i8.  Cast the element type to metadata or wtable if its not that type
already.

rdar://109540863

Author: nate-chandler

lib/IRGen/GenPack.cpp

@@ -454,6 +454,8 @@ irgen::emitTypeMetadataPack(IRGenFunction &IGF,
   auto pack = IGF.emitDynamicAlloca(IGF.IGM.TypeMetadataPtrTy, shape,
                                     IGF.IGM.getPointerAlignment(),
                                     /*allowTaskAlloc=*/true);
+  pack = pack.withAddress(IGF.Builder.CreateElementBitCast(
+      pack.getAddress(), IGF.IGM.TypeMetadataPtrTy));
 
   auto visitFn =
     [&](CanType eltTy, unsigned staticIndex,
@@ -582,6 +584,8 @@ StackAddress irgen::emitWitnessTablePack(IRGenFunction &IGF,
   auto pack = IGF.emitDynamicAlloca(IGF.IGM.WitnessTablePtrTy, shape,
                                     IGF.IGM.getPointerAlignment(),
                                     /*allowTaskAlloc=*/true);
+  pack = pack.withAddress(IGF.Builder.CreateElementBitCast(
+      pack.getAddress(), IGF.IGM.WitnessTablePtrTy));
 
   auto index = 0;
   auto visitFn = [&](CanType eltTy, unsigned staticIndex,

validation-test/IRGen/rdar109540863.swift

@@ -0,0 +1,21 @@
+// RUN: %target-swift-frontend %s -emit-ir | %FileCheck %s
+
+// CHECK: define {{.*}}@callee
+@_silgen_name("callee")
+func callee<each T : P>(_ ts: repeat each T) async {
+  (repeat (each ts).foo())
+}
+
+// CHECK: define {{.*}}@caller
+@_silgen_name("caller")
+func caller<each T1 : P>(t1: repeat each T1) async {
+  await callee(S(), repeat each t1)
+}
+
+struct S : P {
+  func foo() {
+  }
+}
+protocol P {
+  func foo()
+}