Add initial big-endian support

Makefile.in

@@ -84,7 +84,11 @@ ifneq ($(XLEN),32)
 	XLEN := 64
 endif
 
-make_tuple = riscv$(1)-unknown-$(2)
+ifeq (@endian@,big)
+ENDIAN_POSTFIX := be
+endif
+
+make_tuple = riscv$(1)$(ENDIAN_POSTFIX)-unknown-$(2)
 LINUX_TUPLE  ?= $(call make_tuple,$(XLEN),linux-gnu)
 NEWLIB_TUPLE ?= $(call make_tuple,$(XLEN),elf)
 MUSL_TUPLE ?= $(call make_tuple,$(XLEN),linux-musl)

README.md

@@ -111,6 +111,15 @@ This option only takes effect for the GNU toolchain.
 The toolchain has an option `--enable-strip` to control strip of host binaries,
 strip is disabled by default.
 
+### Big Endian configuration
+
+To build either cross-compiler with support for big endian targets, run the following command:
+
+```
+./configure --prefix=/opt/riscv --with-endian=big
+make (target)
+```
+
 ### Troubleshooting Build Problems
 
 Builds work best if installing into an empty directory.  If you build a

configure

@@ -641,6 +641,7 @@ configure_host
 target_cxxflags
 target_cflags
 cmodel
+endian
 gcc_checking
 musl_multilib_names
 newlib_multilib_names
@@ -730,6 +731,7 @@ with_multilib_generator
 with_extra_multilib_test
 enable_gcc_checking
 with_cmodel
+with_endian
 with_target_cflags
 with_target_cxxflags
 with_host
@@ -1426,6 +1428,7 @@ Optional Packages:
                           --with-extra-multilib-test="rv64gcv-lp64;rv64gcv_zba-lp64"
   --with-cmodel           Select the code model to use when building libc and
                           libgcc [--with-cmodel=medlow]
+  --with-endian           Select the target endianess [--with-endian=little]
   --with-target-cflags    Add extra target flags for C for library code
   --with-target-cxxflags  Add extra target flags for C++ for library code
   --with-host=x86_64-w64-mingw32
@@ -4080,6 +4083,19 @@ WITH_SIM=$with_sim
 WITH_LANGUAGES=$with_languages
 
 
+# Check whether --with-endian was given.
+if test "${with_endian+set}" = set; then :
+  withval=$with_endian;
+fi
+
+if test "x$with_endian" != x; then :
+  endian=$with_endian
+
+else
+  endian=little
+
+fi
+
 # Check whether --enable-multilib was given.
 if test ${enable_multilib+y}
 then :
@@ -4138,7 +4154,12 @@ fi
 
 if test "x$enable_multilib" = xyes
 then :
-  glibc_multilib_names="rv32imac-ilp32 rv32gc-ilp32d rv64imac-lp64 rv64gc-lp64d rv64gcv-lp64d"
+  glibc_multilib_names="rv32imac-ilp32 rv32gc-ilp32d rv64imac-lp64 rv64gc-lp64d"
+  # Vector extension is currently not supported on Big-endian systems. 
+  if test "x$endian" = xlittle
+  then :
+       glibc_multilib_names+=" rv64gcv-lp64d"
+  fi
 
 else $as_nop
   glibc_multilib_names="$with_arch-$with_abi"
@@ -4164,16 +4185,18 @@ else $as_nop
 fi
 
 # Check whether --enable-gcc-checking was given.
-if test ${enable_gcc_checking+y}
+if test ${enable_gcc_checking+y} && test "x$endian" = xlittle
 then :
   enableval=$enable_gcc_checking;
 fi
 
-
-if test "x$enable_gcc_checking" = xyes
+# FIXME: Stage1 self-tests fail on BE builds due to lack of RVV support. Disable them for now.
+if test "x$enable_gcc_checking" = xyes && "x$endian" = xlittle
 then :
   gcc_checking=--enable-checking
-
+elif test "x$endian" = xbig
+then :
+  gcc_checking="--enable-checking=no --disable-stage1-checking"
 else $as_nop
   gcc_checking=""
 

configure.ac

@@ -188,6 +188,10 @@ AS_IF([test "x$with_cmodel" != xno],
 	[AC_SUBST(cmodel, -mcmodel=$with_cmodel)],
 	[AC_SUBST(cmodel, -mcmodel=medlow)])
 
+AS_IF([test "x$with_endian" != x],
+	[AC_SUBST(endian, endian=$with_endian)],
+	[AC_SUBST(endian, endian=little)])
+
 AC_ARG_WITH(target_cflags,
 	[AS_HELP_STRING([--with-target-cflags],
 		[Add extra target flags for C for library code])],