RISC-V: Add riscv{32,64}be with big endian as default

gcc/
	* common/config/riscv/riscv-common.c
	(TARGET_DEFAULT_TARGET_FLAGS): Set default endianness.
	* config.gcc (riscv32be-*, riscv64be-*): Set
	TARGET_BIG_ENDIAN_DEFAULT to 1.
	* config/riscv/elf.h (LINK_SPEC): Change -melf* value
	depending on default endianness.
	* config/riscv/freebsd.h (LINK_SPEC): Likewise.
	* config/riscv/linux.h (LINK_SPEC): Likewise.
	* config/riscv/riscv.c (TARGET_DEFAULT_TARGET_FLAGS): Set
	default endianness.
	* config/riscv/riscv.h (DEFAULT_ENDIAN_SPEC): New macro.

gcc/common/config/riscv/riscv-common.c

@@ -32,6 +32,11 @@ along with GCC; see the file COPYING3.  If not see
 #include "config/riscv/riscv-protos.h"
 #include "config/riscv/riscv-subset.h"
 
+#ifdef  TARGET_BIG_ENDIAN_DEFAULT
+#undef  TARGET_DEFAULT_TARGET_FLAGS
+#define TARGET_DEFAULT_TARGET_FLAGS (MASK_BIG_ENDIAN)
+#endif
+
 /* Type for implied ISA info.  */
 struct riscv_implied_info_t
 {

gcc/config.gcc

@@ -2468,6 +2468,11 @@ riscv*-*-linux*)
 	tmake_file="${tmake_file} riscv/t-riscv riscv/t-linux"
 	gnu_ld=yes
 	gas=yes
+	case $target in
+	riscv32be-*|riscv64be-*)
+		tm_defines="${tm_defines} TARGET_BIG_ENDIAN_DEFAULT=1"
+		;;
+	esac
 	# Force .init_array support.  The configure script cannot always
 	# automatically detect that GAS supports it, yet we require it.
 	gcc_cv_initfini_array=yes
@@ -2491,6 +2496,11 @@ riscv*-*-elf* | riscv*-*-rtems*)
 	tmake_file="${tmake_file} riscv/t-riscv"
 	gnu_ld=yes
 	gas=yes
+	case $target in
+	riscv32be-*|riscv64be-*)
+		tm_defines="${tm_defines} TARGET_BIG_ENDIAN_DEFAULT=1"
+		;;
+	esac
 	# Force .init_array support.  The configure script cannot always
 	# automatically detect that GAS supports it, yet we require it.
 	gcc_cv_initfini_array=yes
@@ -2500,6 +2510,11 @@ riscv*-*-freebsd*)
 	tmake_file="${tmake_file} riscv/t-riscv"
 	gnu_ld=yes
 	gas=yes
+	case $target in
+	riscv32be-*|riscv64be-*)
+		tm_defines="${tm_defines} TARGET_BIG_ENDIAN_DEFAULT=1"
+		;;
+	esac
 	# Force .init_array support.  The configure script cannot always
 	# automatically detect that GAS supports it, yet we require it.
 	gcc_cv_initfini_array=yes

gcc/config/riscv/elf.h

@@ -18,7 +18,7 @@ along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */
 
 #define LINK_SPEC "\
--melf" XLEN_SPEC "lriscv \
+-melf" XLEN_SPEC DEFAULT_ENDIAN_SPEC "riscv \
 %{mno-relax:--no-relax} \
 %{mbig-endian:-EB} \
 %{mlittle-endian:-EL} \

gcc/config/riscv/freebsd.h

@@ -40,7 +40,7 @@ along with GCC; see the file COPYING3.  If not see
 
 #undef LINK_SPEC
 #define LINK_SPEC "						\
-  -melf" XLEN_SPEC "lriscv					\
+  -melf" XLEN_SPEC DEFAULT_ENDIAN_SPEC "riscv			\
   %{p:%nconsider using `-pg' instead of `-p' with gprof (1)}	\
   %{v:-V}							\
   %{assert*} %{R*} %{rpath*} %{defsym*}				\

gcc/config/riscv/linux.h

@@ -58,7 +58,7 @@ along with GCC; see the file COPYING3.  If not see
   "%{mabi=ilp32:_ilp32}"
 
 #define LINK_SPEC "\
--melf" XLEN_SPEC "lriscv" LD_EMUL_SUFFIX " \
+-melf" XLEN_SPEC DEFAULT_ENDIAN_SPEC "riscv" LD_EMUL_SUFFIX " \
 %{mno-relax:--no-relax} \
 %{mbig-endian:-EB} \
 %{mlittle-endian:-EL} \

gcc/config/riscv/riscv.c

@@ -5526,6 +5526,11 @@ riscv_asan_shadow_offset (void)
 #undef TARGET_ASAN_SHADOW_OFFSET
 #define TARGET_ASAN_SHADOW_OFFSET riscv_asan_shadow_offset
 
+#ifdef TARGET_BIG_ENDIAN_DEFAULT
+#undef  TARGET_DEFAULT_TARGET_FLAGS
+#define TARGET_DEFAULT_TARGET_FLAGS (MASK_BIG_ENDIAN)
+#endif
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-riscv.h"

gcc/config/riscv/riscv.h

@@ -30,6 +30,12 @@ along with GCC; see the file COPYING3.  If not see
 /* Target CPU versions for D.  */
 #define TARGET_D_CPU_VERSIONS riscv_d_target_versions
 
+#ifdef TARGET_BIG_ENDIAN_DEFAULT
+#define DEFAULT_ENDIAN_SPEC    "b"
+#else
+#define DEFAULT_ENDIAN_SPEC    "l"
+#endif
+
 /* Default target_flags if no switches are specified  */
 
 #ifndef TARGET_DEFAULT