cmake: Pass optimization flag to linker too

The linker may want to know the desired optimization level as when
the multilib configuration includes -Os as a selector.

Adopt the same pattern as the assembler optimization flags by allowing
toolchains to specify linker optimization flags which default to the
compiler optimization flags and the apply those using add_link_options.

Signed-off-by: Keith Packard <keithp@keithp.com>

Author: keith-packard

CMakeLists.txt

@@ -226,6 +226,12 @@ get_property(ASM_OPTIMIZE_FOR_SPEED_FLAG TARGET asm PROPERTY optimization_speed)
 get_property(ASM_OPTIMIZE_FOR_SIZE_FLAG  TARGET asm PROPERTY optimization_size)
 get_property(ASM_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG TARGET asm PROPERTY optimization_size_aggressive)
 
+get_property(LINKER_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG TARGET linker PROPERTY no_optimization)
+get_property(LINKER_OPTIMIZE_FOR_DEBUG_FLAG TARGET linker PROPERTY optimization_debug)
+get_property(LINKER_OPTIMIZE_FOR_SPEED_FLAG TARGET linker PROPERTY optimization_speed)
+get_property(LINKER_OPTIMIZE_FOR_SIZE_FLAG  TARGET linker PROPERTY optimization_size)
+get_property(LINKER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG TARGET linker PROPERTY optimization_size_aggressive)
+
 # Let the assembler inherit the optimization flags of the compiler if it is
 # not set explicitly.
 if(NOT ASM_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG)
@@ -244,23 +250,46 @@ if(NOT ASM_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG)
   set(ASM_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG ${COMPILER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG})
 endif()
 
+# Let the linker inherit the optimization flags of the compiler if it is
+# not set explicitly.
+if(NOT LINKER_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG)
+  set(LINKER_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG ${COMPILER_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
+endif()
+if(NOT LINKER_OPTIMIZE_FOR_DEBUG_FLAG)
+  set(LINKER_OPTIMIZE_FOR_DEBUG_FLAG ${COMPILER_OPTIMIZE_FOR_DEBUG_FLAG})
+endif()
+if(NOT LINKER_OPTIMIZE_FOR_SPEED_FLAG)
+  set(LINKER_OPTIMIZE_FOR_SPEED_FLAG ${COMPILER_OPTIMIZE_FOR_SPEED_FLAG})
+endif()
+if(NOT LINKER_OPTIMIZE_FOR_SIZE_FLAG)
+  set(LINKER_OPTIMIZE_FOR_SIZE_FLAG ${COMPILER_OPTIMIZE_FOR_SIZE_FLAG})
+endif()
+if(NOT LINKER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG)
+  set(LINKER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG ${COMPILER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG})
+endif()
+
 # From kconfig choice, pick the actual OPTIMIZATION_FLAG to use.
 # Kconfig choice ensures only one of these CONFIG_*_OPTIMIZATIONS is set.
 if(CONFIG_NO_OPTIMIZATIONS)
   set(COMPILER_OPTIMIZATION_FLAG ${COMPILER_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
   set(ASM_OPTIMIZATION_FLAG ${ASM_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
+  set(LINKER_OPTIMIZATION_FLAG ${LINKER_OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
 elseif(CONFIG_DEBUG_OPTIMIZATIONS)
   set(COMPILER_OPTIMIZATION_FLAG ${COMPILER_OPTIMIZE_FOR_DEBUG_FLAG})
   set(ASM_OPTIMIZATION_FLAG ${ASM_OPTIMIZE_FOR_DEBUG_FLAG})
+  set(LINKER_OPTIMIZATION_FLAG ${LINKER_OPTIMIZE_FOR_DEBUG_FLAG})
 elseif(CONFIG_SPEED_OPTIMIZATIONS)
   set(COMPILER_OPTIMIZATION_FLAG ${COMPILER_OPTIMIZE_FOR_SPEED_FLAG})
   set(ASM_OPTIMIZATION_FLAG ${ASM_OPTIMIZE_FOR_SPEED_FLAG})
+  set(LINKER_OPTIMIZATION_FLAG ${LINKER_OPTIMIZE_FOR_SPEED_FLAG})
 elseif(CONFIG_SIZE_OPTIMIZATIONS)
   set(COMPILER_OPTIMIZATION_FLAG ${COMPILER_OPTIMIZE_FOR_SIZE_FLAG}) # Default in kconfig
   set(ASM_OPTIMIZATION_FLAG ${ASM_OPTIMIZE_FOR_SIZE_FLAG})
+  set(LINKER_OPTIMIZATION_FLAG ${LINKER_OPTIMIZE_FOR_SIZE_FLAG})
 elseif(CONFIG_SIZE_OPTIMIZATIONS_AGGRESSIVE)
   set(COMPILER_OPTIMIZATION_FLAG ${COMPILER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG})
   set(ASM_OPTIMIZATION_FLAG ${ASM_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG})
+  set(LINKER_OPTIMIZATION_FLAG ${LINKER_OPTIMIZE_FOR_SIZE_AGGRESSIVE_FLAG})
 else()
   message(FATAL_ERROR
     "Unreachable code. Expected optimization level to have been chosen. See Kconfig.zephyr")
@@ -277,6 +306,7 @@ endif()
 zephyr_compile_options($<$<COMPILE_LANGUAGE:ASM>:${ASM_OPTIMIZATION_FLAG}>)
 zephyr_compile_options($<$<COMPILE_LANGUAGE:C>:${COMPILER_OPTIMIZATION_FLAG}>)
 zephyr_compile_options($<$<COMPILE_LANGUAGE:CXX>:${COMPILER_OPTIMIZATION_FLAG}>)
+add_link_options(${LINKER_OPTIMIZATION_FLAG})
 
 if(CONFIG_LTO)
   zephyr_compile_options($<TARGET_PROPERTY:compiler,optimization_lto>)