Build: Add LLVM toolchain support for an521 only.

Support for other platforms will follow.

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: Id036ecd78bf8e8909af30f78b2bfe5262b78c6b9
diff --git a/toolchain_LLVM.cmake b/toolchain_LLVM.cmake
new file mode 100644
index 0000000..d0f88f7
--- /dev/null
+++ b/toolchain_LLVM.cmake
@@ -0,0 +1,257 @@
+#-------------------------------------------------------------------------------
+# SPDX-License-Identifier: BSD-3-Clause
+# SPDX-FileCopyrightText: Copyright The TrustedFirmware-M Contributors
+#-------------------------------------------------------------------------------
+
+set(CMAKE_SYSTEM_NAME Generic)
+
+# Specify the cross compiler
+set(CMAKE_C_COMPILER clang)
+set(CMAKE_C_COMPILER_TARGET ${CROSS_COMPILE})
+
+set(CMAKE_ASM_COMPILER clang)
+set(CMAKE_ASM_COMPILER_TARGET ${CROSS_COMPILE})
+
+set(LINKER_VENEER_OUTPUT_FLAG -Wl,--cmse-implib,--out-implib=)
+set(COMPILER_CMSE_FLAG -mcmse -mfix-cmse-cve-2021-35465)
+
+set(CMAKE_USER_MAKE_RULES_OVERRIDE ${CMAKE_CURRENT_LIST_DIR}/cmake/set_extensions.cmake)
+
+# CMAKE_C_COMPILER_VERSION is not guaranteed to be defined.
+EXECUTE_PROCESS( COMMAND ${CMAKE_C_COMPILER} -dumpversion OUTPUT_VARIABLE LLVM_VERSION )
+if (LLVM_VERSION VERSION_LESS 18.1.3)
+    message(FATAL_ERROR "Please use newer LLVM compiler version starting from 18.1.3")
+endif()
+
+# ===================== Set toolchain CPU and Arch =============================
+# -mcpu gives better optimisation than -march so -mcpu shall be in preference
+
+if (TFM_SYSTEM_PROCESSOR)
+    if(TFM_SYSTEM_DSP)
+        string(APPEND TFM_SYSTEM_PROCESSOR "+dsp")
+    else()
+        string(APPEND TFM_SYSTEM_PROCESSOR "+nodsp")
+    endif()
+    if(CONFIG_TFM_ENABLE_FP)
+        string(APPEND TFM_SYSTEM_PROCESSOR "+fp")
+    else()
+        string(APPEND TFM_SYSTEM_PROCESSOR "+nofp")
+    endif()
+
+    set(CMAKE_C_FLAGS        "-mcpu=${TFM_SYSTEM_PROCESSOR}")
+    set(CMAKE_ASM_FLAGS      "-mcpu=${TFM_SYSTEM_PROCESSOR}")
+else()
+    if(CONFIG_TFM_ENABLE_FP)
+        string(APPEND TFM_SYSTEM_ARCHITECTURE "+fp")
+    endif()
+    if(NOT TFM_SYSTEM_DSP)
+        string(APPEND TFM_SYSTEM_ARCHITECTURE "+nodsp")
+    endif()
+    set(CMAKE_C_FLAGS        "-march=${TFM_SYSTEM_ARCHITECTURE}")
+    set(CMAKE_CXX_FLAGS      "-march=${TFM_SYSTEM_ARCHITECTURE}")
+    set(CMAKE_ASM_FLAGS      "-march=${TFM_SYSTEM_ARCHITECTURE}")
+    set(CMAKE_ASM_CPU_FLAG  ${TFM_SYSTEM_ARCHITECTURE})
+endif()
+
+if (CONFIG_TFM_FLOAT_ABI STREQUAL "hard")
+    set(COMPILER_CP_FLAG -mfloat-abi=hard)
+    set(LINKER_CP_OPTION -mfloat-abi=hard)
+    if (CONFIG_TFM_ENABLE_FP OR CONFIG_TFM_ENABLE_MVE_FP)
+        set(COMPILER_CP_FLAG -mfloat-abi=hard -mfpu=${CONFIG_TFM_FP_ARCH})
+        set(LINKER_CP_OPTION -mfloat-abi=hard -mfpu=${CONFIG_TFM_FP_ARCH})
+    endif()
+else()
+    set(COMPILER_CP_FLAG -mfloat-abi=soft)
+    set(LINKER_CP_OPTION -mfloat-abi=soft)
+endif()
+
+set(BL1_COMPILER_CP_FLAG -mfloat-abi=soft)
+set(BL1_LINKER_CP_OPTION -mfloat-abi=soft)
+
+set(BL2_COMPILER_CP_FLAG -mfloat-abi=soft)
+set(BL2_LINKER_CP_OPTION -mfloat-abi=soft)
+
+add_compile_options(
+     -Wno-ignored-optimization-argument
+     -Wno-unused-command-line-argument
+     -Wall
+     -Wno-error=cpp
+     -c
+     -fdata-sections
+     -ffunction-sections
+     -fno-builtin
+     -fshort-enums
+     -fshort-wchar
+     -funsigned-char
+     -std=c99
+)
+
+# Pointer Authentication Code and Branch Target Identification (PACBTI) Options
+# Not currently supported for LLVM.
+if(NOT ${CONFIG_TFM_BRANCH_PROTECTION_FEAT} STREQUAL BRANCH_PROTECTION_DISABLED)
+    message(FATAL_ERROR "BRANCH_PROTECTION NOT supported for LLVM")
+endif()
+
+add_link_options(
+    -lclang_rt.builtins   # needed for  __aeabi_memclr4(), __aeabi_memclr8(), __aeabi_memcpy4()
+    LINKER:-check-sections
+    LINKER:-fatal-warnings
+    LINKER:--gc-sections
+)
+
+if(NOT CONFIG_TFM_MEMORY_USAGE_QUIET)
+    add_link_options(LINKER:--print-memory-usage)
+endif()
+
+# Macro for adding scatter files. Supports multiple files
+macro(target_add_scatter_file target)
+    target_link_options(${target} PRIVATE -T $<TARGET_OBJECTS:${target}_scatter>)
+
+    add_library(${target}_scatter OBJECT)
+    foreach(scatter_file ${ARGN})
+        target_sources(${target}_scatter
+            PRIVATE
+                ${scatter_file}
+        )
+        # Cmake cannot use generator expressions in the
+        # set_source_file_properties command, so instead we just parse the regex
+        # for the filename and set the property on all files, regardless of if
+        # the generator expression would evaluate to true or not.
+        string(REGEX REPLACE ".*>:(.*)>$" "\\1" SCATTER_FILE_PATH "${scatter_file}")
+        set_source_files_properties(${SCATTER_FILE_PATH}
+            PROPERTIES
+            LANGUAGE C
+            KEEP_EXTENSION True # Don't use .o extension for the preprocessed file
+        )
+    endforeach()
+
+    add_dependencies(${target} ${target}_scatter)
+
+    set_property(TARGET ${target} APPEND PROPERTY LINK_DEPENDS $<TARGET_OBJECTS:${target}_scatter>)
+
+    target_link_libraries(${target}_scatter
+        platform_region_defs
+        psa_interface
+        tfm_config
+    )
+
+    target_compile_options(${target}_scatter PRIVATE -E -P -xc)
+endmacro()
+
+# Macro for converting the output *.axf file to finary files: bin, elf, hex
+macro(add_convert_to_bin_target target)
+    get_target_property(bin_dir ${target} RUNTIME_OUTPUT_DIRECTORY)
+    add_custom_target(${target}_bin
+        ALL DEPENDS ${target}
+        COMMAND ${CMAKE_OBJCOPY} -O binary $<TARGET_FILE:${target}> ${bin_dir}/${target}.bin
+        COMMAND ${CMAKE_OBJCOPY} -O elf32-littlearm $<TARGET_FILE:${target}> ${bin_dir}/${target}.elf
+        COMMAND ${CMAKE_OBJCOPY} -O ihex $<TARGET_FILE:${target}> ${bin_dir}/${target}.hex
+    )
+endmacro()
+
+# Set of macrots for sharing code between BL2 and RunTime, targeted for sharing MbedTLS library
+macro(target_share_symbols target)
+    get_target_property(TARGET_TYPE ${target} TYPE)
+    if (NOT TARGET_TYPE STREQUAL "EXECUTABLE")
+        message(FATAL_ERROR "${target} is not an executable. Symbols cannot be shared from libraries.")
+    endif()
+
+    foreach(symbol_file ${ARGN})
+        FILE(STRINGS ${symbol_file} SYMBOLS
+            LENGTH_MINIMUM 1
+        )
+        list(APPEND KEEP_SYMBOL_LIST ${SYMBOLS})
+    endforeach()
+
+    set(STRIP_SYMBOL_KEEP_LIST ${KEEP_SYMBOL_LIST})
+
+    # Force the target to not remove the symbols if they're unused.
+    list(TRANSFORM KEEP_SYMBOL_LIST PREPEND "-Wl,--undefined=")
+    target_link_options(${target}
+        PRIVATE
+            ${KEEP_SYMBOL_LIST}
+    )
+
+    list(TRANSFORM STRIP_SYMBOL_KEEP_LIST PREPEND  --keep-symbol=)
+    # strip all the symbols except those proveded as arguments
+    add_custom_target(${target}_shared_symbols
+        COMMAND ${CMAKE_OBJCOPY}
+            $<TARGET_FILE:${target}>
+            --wildcard ${STRIP_SYMBOL_KEEP_LIST}
+            --strip-all
+            $<TARGET_FILE_DIR:${target}>/${target}${CODE_SHARING_OUTPUT_FILE_SUFFIX}
+    )
+
+    # Ensure ${target} is built before $<TARGET_FILE:${target}> is used to generate ${target}_shared_symbols
+    add_dependencies(${target}_shared_symbols ${target})
+    # Allow the global clean target to rm the ${target}_shared_symbols created
+    set_target_properties(${target}_shared_symbols PROPERTIES
+        ADDITIONAL_CLEAN_FILES $<TARGET_FILE_DIR:${target}>/${target}${CODE_SHARING_OUTPUT_FILE_SUFFIX}
+    )
+endmacro()
+
+macro(target_link_shared_code target)
+    foreach(symbol_provider ${ARGN})
+        if (TARGET ${symbol_provider})
+            get_target_property(SYMBOL_PROVIDER_TYPE ${symbol_provider} TYPE)
+            if (NOT SYMBOL_PROVIDER_TYPE STREQUAL "EXECUTABLE")
+                message(FATAL_ERROR "${symbol_provider} is not an executable. Symbols cannot be shared from libraries.")
+            endif()
+        endif()
+
+        # Ensure ${symbol_provider}_shared_symbols is built before ${target}
+        add_dependencies(${target} ${symbol_provider}_shared_symbols)
+        # ${symbol_provider}_shared_symbols - a custom target is always considered out-of-date
+        # To only link when necessary, depend on ${symbol_provider} instead
+        set_property(TARGET ${target} APPEND PROPERTY LINK_DEPENDS $<TARGET_OBJECTS:${symbol_provider}>)
+        target_link_options(${target} PRIVATE LINKER:-R$<TARGET_FILE_DIR:${symbol_provider}>/${symbol_provider}${CODE_SHARING_INPUT_FILE_SUFFIX})
+    endforeach()
+endmacro()
+
+macro(target_strip_symbols target)
+    set(SYMBOL_LIST "${ARGN}")
+    list(TRANSFORM SYMBOL_LIST PREPEND  --strip-symbol=)
+
+    add_custom_command(
+        TARGET ${target}
+        POST_BUILD
+        COMMAND ${CMAKE_OBJCOPY}
+        ARGS $<TARGET_FILE:${target}> --wildcard ${SYMBOL_LIST} $<TARGET_FILE:${target}>
+    )
+endmacro()
+
+macro(target_strip_symbols_from_dependency target dependency)
+    set(SYMBOL_LIST "${ARGN}")
+    list(TRANSFORM SYMBOL_LIST PREPEND  --strip-symbol=)
+
+    add_custom_command(
+        TARGET ${target}
+        PRE_LINK
+        COMMAND ${CMAKE_OBJCOPY}
+        ARGS $<TARGET_FILE:${dependency}> --wildcard ${SYMBOL_LIST} $<TARGET_FILE:${dependency}>
+    )
+endmacro()
+
+macro(target_weaken_symbols target)
+    set(SYMBOL_LIST "${ARGN}")
+    list(TRANSFORM SYMBOL_LIST PREPEND  --weaken-symbol=)
+
+    add_custom_command(
+        TARGET ${target}
+        POST_BUILD
+        COMMAND ${CMAKE_OBJCOPY}
+        ARGS $<TARGET_FILE:${target}> --wildcard ${SYMBOL_LIST} $<TARGET_FILE:${target}>
+    )
+endmacro()
+
+macro(target_weaken_symbols_from_dependency target dependency)
+    set(SYMBOL_LIST "${ARGN}")
+    list(TRANSFORM SYMBOL_LIST PREPEND  --weaken-symbol=)
+
+    add_custom_command(
+        TARGET ${target}
+        PRE_LINK
+        COMMAND ${CMAKE_OBJCOPY}
+        ARGS $<TARGET_FILE:${dependency}> --wildcard ${SYMBOL_LIST} $<TARGET_FILE:${dependency}>
+    )
+endmacro()