riscv: toolchain arguments for a 64-bit build

For now we enforce the medany code model for 64-bit builds as we get
reloc issues otherwise. The instruction set and ABI are also set to
soft-float usage.

The ilp32 ABI is explicitly specified on 32-bit build to make sure
it is not using a wrong default if the same toolchain is used for both
32- and 64-bit builds. The archittecture options are the same as the
SDK's riscv32 toolchain default in that case.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>

arch/riscv/CMakeLists.txt

@@ -2,4 +2,8 @@
 
 add_subdirectory(core)
 
+if(CONFIG_64BIT)
+set_property(GLOBAL PROPERTY PROPERTY_OUTPUT_FORMAT elf64-littleriscv)
+else()
 set_property(GLOBAL PROPERTY PROPERTY_OUTPUT_FORMAT elf32-littleriscv)
+endif()

cmake/compiler/gcc/target.cmake

@@ -69,6 +69,12 @@ elseif("${ARCH}" STREQUAL "arc")
   list(APPEND TOOLCHAIN_C_FLAGS
     -mcpu=${GCC_M_CPU}
     )
+elseif("${ARCH}" STREQUAL "riscv")
+  if(CONFIG_64BIT)
+    list(APPEND TOOLCHAIN_C_FLAGS -mabi=lp64 -march=rv64imac -mcmodel=medany)
+  else()
+    list(APPEND TOOLCHAIN_C_FLAGS -mabi=ilp32 -march=rv32ima)
+  endif()
 endif()
 
 if(NOT no_libgcc)