RISCV compiler: Set mabi and march via Kconfig options

The mabi and march options of the compiler and linker commands
were previously hardcoded and depended only on the 64BIT config
option. This update allows these flags to be set by the config
options currently available, plus an additional option to
specify the compressed ISA.

Signed-off-by: Jaron Kelleher <jkelleher@fb.com>

arch/riscv/Kconfig

@@ -9,6 +9,10 @@ config ARCH
 	default "riscv64" if 64BIT
 	default "riscv32"
 
+config COMPRESSED_ISA
+	bool
+	default y if 64BIT
+
 menu "RISCV Processor Options"
 
 config INCLUDE_RESET_VECTOR

cmake/compiler/gcc/target.cmake

@@ -49,11 +49,7 @@ elseif("${ARCH}" STREQUAL "arc")
     -mcpu=${GCC_M_CPU}
     )
 elseif("${ARCH}" STREQUAL "riscv")
-  if(CONFIG_64BIT)
-    list(APPEND TOOLCHAIN_C_FLAGS -mabi=lp64 -march=rv64imac -mcmodel=medany)
-  else()
-    list(APPEND TOOLCHAIN_C_FLAGS -mabi=ilp32 -march=rv32ima)
-  endif()
+  include(${CMAKE_CURRENT_LIST_DIR}/target_riscv.cmake)
 elseif("${ARCH}" STREQUAL "x86")
   include(${CMAKE_CURRENT_LIST_DIR}/target_x86.cmake)
 endif()

cmake/compiler/gcc/target_riscv.cmake

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: Apache-2.0
+
+set(riscv_mabi "lp")
+set(riscv_march "rv")
+
+if(CONFIG_64BIT)
+    string(CONCAT riscv_mabi  ${riscv_mabi} "64")
+    string(CONCAT riscv_march ${riscv_march} "64ima")
+    list(APPEND TOOLCHAIN_C_FLAGS -mcmodel=medany)
+else()
+    string(CONCAT riscv_mabi  "i" ${riscv_mabi} "32")
+    string(CONCAT riscv_march ${riscv_march} "32ima")
+endif()
+
+if(CONFIG_FLOAT)
+    string(CONCAT riscv_march ${riscv_march} "f")
+endif()
+
+if(CONFIG_COMPRESSED_ISA)
+    string(CONCAT riscv_march ${riscv_march} "c")
+endif()
+
+list(APPEND TOOLCHAIN_C_FLAGS -mabi=${riscv_mabi} -march=${riscv_march})
+list(APPEND TOOLCHAIN_LD_FLAGS -mabi=${riscv_mabi} -march=${riscv_march})