[PATCH] [AArch64] Fix PR gdb/28681

[Luis Machado via Gdb-patches <gdb-patches@sourceware.org>]

This is the same as commit b1718fcdd1d2a5c514f8ee504ba07fb3f42b8608, but
fixing things for AArch64.

With the patch, gdb.cp/non-trivial-retval.exp has full passes on
AArch64-Linux Ubuntu 20.04/18.04.
---
 gdb/aarch64-tdep.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 70fb66954a4..802762f303c 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -2323,6 +2323,15 @@ aarch64_extract_return_value (struct type *type, struct regcache *regs,
 	  valbuf += X_REGISTER_SIZE;
 	}
     }
+  else if (!language_pass_by_reference (type).trivially_copyable)
+    {
+      /* If the object is a non-trivial C++ object, the result is passed as a
+	 pointer stored in X0.  */
+      CORE_ADDR addr;
+
+      regs->cooked_read (AARCH64_X0_REGNUM, &addr);
+      read_memory (addr, valbuf, TYPE_LENGTH (type));
+    }
   else
     {
       /* For a structure or union the behaviour is as if the value had
-- 
2.25.1