[Async CC] Auth'd AFP ptr to load ptr from FunctionPointer.

In FunctionPointer::getPointer, in the case that the FunctionPointer is
actually a pointer to an AsyncFunctionPointer struct, the relative
address of the function must be loaded from the AsyncFunctionPointer
struct.  Doing so requires authentication that pointer to the
AsyncFunctionPointer struct.  Here, that authentication is done.

Author: nate-chandler

lib/IRGen/GenCall.cpp

@@ -4539,18 +4539,25 @@ llvm::Value *FunctionPointer::getPointer(IRGenFunction &IGF) const {
     return Value;
   case KindTy::Value::AsyncFunctionPointer: {
     if (!isFunctionPointerWithoutContext) {
+      auto *fnPtr = Value;
+      if (auto authInfo = AuthInfo) {
+        fnPtr = emitPointerAuthAuth(IGF, fnPtr, authInfo);
+      }
       auto *descriptorPtr =
-          IGF.Builder.CreateBitCast(Value, IGF.IGM.AsyncFunctionPointerPtrTy);
+          IGF.Builder.CreateBitCast(fnPtr, IGF.IGM.AsyncFunctionPointerPtrTy);
       auto *addrPtr = IGF.Builder.CreateStructGEP(descriptorPtr, 0);
-      return IGF.emitLoadOfRelativePointer(
+      auto *result = IGF.emitLoadOfRelativePointer(
           Address(addrPtr, IGF.IGM.getPointerAlignment()), /*isFar*/ false,
           /*expectedType*/ getFunctionType()->getPointerTo());
+      if (auto authInfo = AuthInfo) {
+        result = emitPointerAuthSign(IGF, result, authInfo);
+      }
+      return result;
     } else {
       return IGF.Builder.CreateBitOrPointerCast(
           Value, getFunctionType()->getPointerTo());
     }
   }
-
   }
 }