[PATCH v1 1/1] CryptoPkg/IntrinsicLib: Fix CLANG38 IA32 build problem

["Xiaoyu Lu" <xiaoyux.lu@intel.com>]

When use clang-3.8 to build the NetworkPkg, compiler optimization
may use memcpy for memory copy. For example:

 CryptoPkg/Library/OpensslLib/openssl/ssl/ssl_rsa.c:918: undefined
 reference to `memcpy'`

Compiler optimization is sophisticated, but we can work around it
use __attribute__((__used__)) to informs the compiler that symbol
should be retained in the object file, even if it may be
unreferenced.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Signed-off-by: Xiaoyu Lu <xiaoyux.lu@intel.com>
---
 CryptoPkg/Library/IntrinsicLib/CopyMem.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/CryptoPkg/Library/IntrinsicLib/CopyMem.c b/CryptoPkg/Library/IntrinsicLib/CopyMem.c
index e29b4918d200..7faf5a34d8c1 100644
--- a/CryptoPkg/Library/IntrinsicLib/CopyMem.c
+++ b/CryptoPkg/Library/IntrinsicLib/CopyMem.c
@@ -10,8 +10,21 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #include <Base.h>
 #include <Library/BaseMemoryLib.h>
 
+#if defined(__clang__) && !defined(__APPLE__)
+
+/* Copies bytes between buffers */
+static __attribute__((__used__))
+void * __memcpy (void *dest, const void *src, unsigned int count)
+{
+  return CopyMem (dest, src, (UINTN)count);
+}
+__attribute__((__alias__("__memcpy")))
+void * memcpy (void *dest, const void *src, unsigned int count);
+
+#else
 /* Copies bytes between buffers */
 void * memcpy (void *dest, const void *src, unsigned int count)
 {
   return CopyMem (dest, src, (UINTN)count);
 }
+#endif
-- 
2.7.4