cmake: add support enhanced variants with multiple compilers

Retain support for older SDK versions by checking for both paths to GNU
toolchains.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

Author: nashif

cmake/modules/FindHostTools.cmake

@@ -95,7 +95,7 @@ zephyr_file(APPLICATION_ROOT TOOLCHAIN_ROOT)
 
 # Host-tools don't unconditionally set TOOLCHAIN_HOME anymore,
 # but in case Zephyr's SDK toolchain is used, set TOOLCHAIN_HOME
-if("${ZEPHYR_TOOLCHAIN_VARIANT}" STREQUAL "zephyr")
+if("${ZEPHYR_TOOLCHAIN_VARIANT}" MATCHES "^zephyr/?")
   set(TOOLCHAIN_HOME ${HOST_TOOLS_HOME})
 endif()
 
@@ -108,12 +108,11 @@ if("${ZEPHYR_TOOLCHAIN_VARIANT}" MATCHES "^([^/]+)/([^/]+)$")
   set(_variant "${CMAKE_MATCH_1}")
   set(_compiler "${CMAKE_MATCH_2}")
   set(ZEPHYR_TOOLCHAIN_VARIANT "${_variant}")
-  set(TOOLCHAIN_VARIANT_COMPILER "${_compiler}")
   set(TOOLCHAIN_VARIANT_COMPILER ${_compiler} CACHE STRING "compiler used by the toolchain variant" FORCE)
 endif()
 
 # Set cached ZEPHYR_TOOLCHAIN_VARIANT.
-set(ZEPHYR_TOOLCHAIN_VARIANT ${ZEPHYR_TOOLCHAIN_VARIANT} CACHE STRING "Zephyr toolchain variant")
+set(ZEPHYR_TOOLCHAIN_VARIANT ${ZEPHYR_TOOLCHAIN_VARIANT} CACHE STRING "Zephyr toolchain variant" FORCE)
 
 # Configure the toolchain based on what SDK/toolchain is in use.
 include(${TOOLCHAIN_ROOT}/cmake/toolchain/${ZEPHYR_TOOLCHAIN_VARIANT}/generic.cmake)

cmake/modules/FindZephyr-sdk.cmake

@@ -54,7 +54,7 @@ endif()
 # 1) Zephyr specified as toolchain (ZEPHYR_SDK_INSTALL_DIR still used if defined)
 # 2) No toolchain specified == Default to Zephyr toolchain
 # Until we completely deprecate it
-if(("zephyr" STREQUAL ${ZEPHYR_TOOLCHAIN_VARIANT}) OR
+if((${ZEPHYR_TOOLCHAIN_VARIANT} MATCHES "^zephyr/?") OR
    (NOT DEFINED ZEPHYR_TOOLCHAIN_VARIANT) OR
    (DEFINED ZEPHYR_SDK_INSTALL_DIR) OR
    (Zephyr-sdk_FIND_REQUIRED))

cmake/toolchain/zephyr/generic.cmake

@@ -1,10 +1,25 @@
 # SPDX-License-Identifier: Apache-2.0
 
-include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/generic.cmake)
+if(TOOLCHAIN_VARIANT_COMPILER STREQUAL "gnu" OR
+    NOT DEFINED TOOLCHAIN_VARIANT_COMPILER)
+  if(EXISTS ${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/gnu/generic.cmake)
+    include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/gnu/generic.cmake)
+  else()
+    include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/generic.cmake)
+  endif()
+  set(TOOLCHAIN_VARIANT_COMPILER "gnu" CACHE STRING "compiler used by the toolchain variant" FORCE)
 
-set(TOOLCHAIN_KCONFIG_DIR ${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr)
+  set(TOOLCHAIN_KCONFIG_DIR ${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr)
+  # Zephyr SDK < 0.17.1 does not set TOOLCHAIN_HAS_GLIBCXX
+  set(TOOLCHAIN_HAS_GLIBCXX ON CACHE BOOL "True if toolchain supports libstdc++")
+  message(STATUS "Found toolchain: zephyr ${SDK_VERSION} (${ZEPHYR_SDK_INSTALL_DIR})")
+elseif(TOOLCHAIN_VARIANT_COMPILER STREQUAL "llvm")
+  include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/llvm/generic.cmake)
+  set(TOOLCHAIN_VARIANT_COMPILER "llvm" CACHE STRING "compiler used by the toolchain variant" FORCE)
 
-# Zephyr SDK < 0.17.1 does not set TOOLCHAIN_HAS_GLIBCXX
-set(TOOLCHAIN_HAS_GLIBCXX ON CACHE BOOL "True if toolchain supports libstdc++")
+  set(TOOLCHAIN_KCONFIG_DIR ${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr)
 
-message(STATUS "Found toolchain: zephyr-sdk-gnu ${SDK_VERSION} (${ZEPHYR_SDK_INSTALL_DIR})")
+  message(STATUS "Found toolchain: zephyr ${SDK_VERSION} (${ZEPHYR_SDK_INSTALL_DIR})")
+else()
+  message(FATAL_ERROR "Unsupported TOOLCHAIN_VARIANT_COMPILER: ${TOOLCHAIN_VARIANT_COMPILER}")
+endif()

cmake/toolchain/zephyr/target.cmake

@@ -1,3 +1,16 @@
 # SPDX-License-Identifier: Apache-2.0
 
-include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/target.cmake)
+if(TOOLCHAIN_VARIANT_COMPILER STREQUAL "gnu" OR
+   TOOLCHAIN_VARIANT_COMPILER STREQUAL "default")
+  set(TOOLCHAIN_VARIANT_COMPILER gnu CACHE STRING "Variant compiler being used")
+  if(EXISTS ${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/gnu/target.cmake)
+    include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/gnu/target.cmake)
+  else()
+    include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/target.cmake)
+  endif()
+elseif (TOOLCHAIN_VARIANT_COMPILER STREQUAL "llvm")
+  set(TOOLCHAIN_VARIANT_COMPILER llvm CACHE STRING "Variant compiler being used")
+  include(${ZEPHYR_SDK_INSTALL_DIR}/cmake/zephyr/llvm/target.cmake)
+else()
+  message(FATAL_ERROR "Unsupported TOOLCHAIN_VARIANT_COMPILER: ${TOOLCHAIN_VARIANT_COMPILER}")
+endif()