Add support for LoongArch (#122)

include/boost/predef/architecture.h

@@ -16,6 +16,7 @@ http://www.boost.org/LICENSE_1_0.txt)
 #include <boost/predef/architecture/convex.h>
 #include <boost/predef/architecture/e2k.h>
 #include <boost/predef/architecture/ia64.h>
+#include <boost/predef/architecture/loongarch.h>
 #include <boost/predef/architecture/m68k.h>
 #include <boost/predef/architecture/mips.h>
 #include <boost/predef/architecture/parisc.h>

include/boost/predef/architecture/loongarch.h

@@ -0,0 +1,41 @@
+/*
+Copyright Zhang Na 2022
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE_1_0.txt or copy at
+http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+#ifndef BOOST_PREDEF_ARCHITECTURE_LOONGARCH_H
+#define BOOST_PREDEF_ARCHITECTURE_LOONGARCH_H
+
+#include <boost/predef/version_number.h>
+#include <boost/predef/make.h>
+
+/* tag::reference[]
+= `BOOST_ARCH_LOONGARCH`
+
+[options="header"]
+|===
+| {predef_symbol} | {predef_version}
+
+| `+__loongarch__+` | {predef_detection}
+|===
+*/ // end::reference[]
+
+#define BOOST_ARCH_LOONGARCH BOOST_VERSION_NUMBER_NOT_AVAILABLE
+
+#if defined(__loongarch__)
+#   undef BOOST_ARCH_LOONGARCH
+#   define BOOST_ARCH_LOONGARCH BOOST_VERSION_NUMBER_AVAILABLE
+#endif
+
+#if BOOST_ARCH_LOONGARCH
+#   define BOOST_ARCH_LOONGARCH_AVAILABLE
+#endif
+
+#define BOOST_ARCH_LOONGARCH_NAME "LoongArch"
+
+#endif
+
+#include <boost/predef/detail/test.h>
+BOOST_PREDEF_DECLARE_TEST(BOOST_ARCH_LOONGARCH,BOOST_ARCH_LOONGARCH_NAME)

include/boost/predef/other/endian.h

@@ -121,6 +121,7 @@ information and acquired knowledge:
         defined(__ARMEL__) || \
         defined(__THUMBEL__) || \
         defined(__AARCH64EL__) || \
+        defined(__loongarch__) || \
         defined(_MIPSEL) || \
         defined(__MIPSEL) || \
         defined(__MIPSEL__) || \